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Editor Work2017 Vol. 25, No. s1
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2017, 25(s1): 1-6.
Abstract
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In the process of excavation of the karst area, the karst pipeline flooding muddy mud seriously affected the normal construction of the foundation pit. According to the example of the karst gushing water treatment project in the deep foundation pit of Yan'an Road, Guiyang Metro Line 2,technology has been studied. Based on the understanding of the hydrogeological characteristics of the karst gushing water area, the plugging method is adopted to select the appropriate grouting material and matching technology to realize the sealing of the gushing water. In the actual grouting work, summed up the experience of the previous grouting failure, the groundwater source and channel for in-depth analysis, on this basis to adjust the grouting design and implementation of the program, and finally through the drilling of auxiliary grouting hole, Karst groundwater connection channel for double liquid grouting to achieve a successful water shutoff. Grouting process control and scheme adjustment have reference for karst pipeline gushing in similar foundation pit engineering.
In the process of excavation of the karst area, the karst pipeline flooding muddy mud seriously affected the normal construction of the foundation pit. According to the example of the karst gushing water treatment project in the deep foundation pit of Yan'an Road, Guiyang Metro Line 2,technology has been studied. Based on the understanding of the hydrogeological characteristics of the karst gushing water area, the plugging method is adopted to select the appropriate grouting material and matching technology to realize the sealing of the gushing water. In the actual grouting work, summed up the experience of the previous grouting failure, the groundwater source and channel for in-depth analysis, on this basis to adjust the grouting design and implementation of the program, and finally through the drilling of auxiliary grouting hole, Karst groundwater connection channel for double liquid grouting to achieve a successful water shutoff. Grouting process control and scheme adjustment have reference for karst pipeline gushing in similar foundation pit engineering.
2017, 25(s1): 7-15.
Karstic water underground have a great threat to tunnel in karst area, such as cause tunnel water gushing, water inrush, mud in rush, etc. Based on the geological investigation, exploration, pumping test, analyzing karstic water development regularity and its distributed characteristics of diversion project nearby Kunming, and providing the basis of design and construction to water diversion project in Yunnan and future underground tunnel project. Investigation and analysis show that karst developed in Permian, Carboniferous, and Devonian, karst distributed banded near a groundwater discharge datum and fault basin, fault valleys, secondly in the fracture location controlled by new tectonic movement and the boundary of different micro hydrogeological unit; in the Permian limestone, groundwater drainage layered, in the Carboniferous and the Devonian that development aven and underground karst channel; in 1900~2150m elevation, karst development intensively, this area is the main runoff area of karstic underground water and have great influence on tunnel, it have potential of water gushing, water inrush, mud in rush, karst collapse and a karst cavity.
Karstic water underground have a great threat to tunnel in karst area, such as cause tunnel water gushing, water inrush, mud in rush, etc. Based on the geological investigation, exploration, pumping test, analyzing karstic water development regularity and its distributed characteristics of diversion project nearby Kunming, and providing the basis of design and construction to water diversion project in Yunnan and future underground tunnel project. Investigation and analysis show that karst developed in Permian, Carboniferous, and Devonian, karst distributed banded near a groundwater discharge datum and fault basin, fault valleys, secondly in the fracture location controlled by new tectonic movement and the boundary of different micro hydrogeological unit; in the Permian limestone, groundwater drainage layered, in the Carboniferous and the Devonian that development aven and underground karst channel; in 1900~2150m elevation, karst development intensively, this area is the main runoff area of karstic underground water and have great influence on tunnel, it have potential of water gushing, water inrush, mud in rush, karst collapse and a karst cavity.
2017, 25(s1): 16-23.
Guizhou is located in the mountain area of the Yunnan-Guizhou Plateau, with the special geographical position and high mountains and steep slopes. Widely distributed carbonate rocks lead to strong karstification, thus cause a large number of slope geological disasters controlled by strong karstification. This paper takes the Xinzhai collapse of Huishui County as a typical example of gently counter-inclined bedding slope in karst area. With the detailed field investigation and discrete element numerical simulation to explore the deformation-failure mechanism. Result shows that the slope controlled by gently counter-inclined and soft and hard layers structure with strong karstification. The slope occurs a concave cavity with the differential dissolution and then makes falling and toppling failure. Along the continuing process of the role of karst and water, the concave cavity expands and the structure plane extends further. Also the slope gradually has an expansion deformation from shallow to deep, finally results in large scale integrity sliding-destruction underlying soft rock. The deformation-failure mechanism is a collapse with periodical characters of differential dissolutionfalling and topplingcreeping and crackingsliding out.
Guizhou is located in the mountain area of the Yunnan-Guizhou Plateau, with the special geographical position and high mountains and steep slopes. Widely distributed carbonate rocks lead to strong karstification, thus cause a large number of slope geological disasters controlled by strong karstification. This paper takes the Xinzhai collapse of Huishui County as a typical example of gently counter-inclined bedding slope in karst area. With the detailed field investigation and discrete element numerical simulation to explore the deformation-failure mechanism. Result shows that the slope controlled by gently counter-inclined and soft and hard layers structure with strong karstification. The slope occurs a concave cavity with the differential dissolution and then makes falling and toppling failure. Along the continuing process of the role of karst and water, the concave cavity expands and the structure plane extends further. Also the slope gradually has an expansion deformation from shallow to deep, finally results in large scale integrity sliding-destruction underlying soft rock. The deformation-failure mechanism is a collapse with periodical characters of differential dissolutionfalling and topplingcreeping and crackingsliding out.
2017, 25(s1): 24-28.
Connectivity can reflect the penetration of fractures in rock mass, and is one of the key parameters of slope stability evaluation. It is of great significance to the prevention and control of engineering geological disasters. H-H connectivity estimation model is based on the principle of H-H trace length estimation model, and is extended to the calculation of lock length. The H-H estimation model belongs to the rectangular window method. When the trace length is estimated by the window method, the results will be affected by the window scale. When the method is extended to the connection rate calculation, the influence of the window scale should be taken into account. Experimentation area is Changchun Jingyue Economic Development Zone Dongsheng quarry, obtain the slope geometry information using digital photogrammetry technology, set the window length of slope inherent length, respectively set the window height is 1, 2, 3, 5, 8, 10, 15, 20, 30meters 9 scale to calculate the connectivity rate, the calculated results were 0.57, 0.35, 0.21, 0.16, 0.10, 0.09, 0.06, 0.05, 0.03 respectively. The results show that with the increase of the window height, the calculation results are reduced gradually, and the window scale has a significant influence on the calculation results.
Connectivity can reflect the penetration of fractures in rock mass, and is one of the key parameters of slope stability evaluation. It is of great significance to the prevention and control of engineering geological disasters. H-H connectivity estimation model is based on the principle of H-H trace length estimation model, and is extended to the calculation of lock length. The H-H estimation model belongs to the rectangular window method. When the trace length is estimated by the window method, the results will be affected by the window scale. When the method is extended to the connection rate calculation, the influence of the window scale should be taken into account. Experimentation area is Changchun Jingyue Economic Development Zone Dongsheng quarry, obtain the slope geometry information using digital photogrammetry technology, set the window length of slope inherent length, respectively set the window height is 1, 2, 3, 5, 8, 10, 15, 20, 30meters 9 scale to calculate the connectivity rate, the calculated results were 0.57, 0.35, 0.21, 0.16, 0.10, 0.09, 0.06, 0.05, 0.03 respectively. The results show that with the increase of the window height, the calculation results are reduced gradually, and the window scale has a significant influence on the calculation results.
2017, 25(s1): 29-34.
In the lower of Shennong river, it is widely covered by carbonatite with strong karstification, which has important influence on the construction of the Yiba highway. This paper takes Shujiacao area for example, researches on the karst development feature by in-site investigation and the data of geophysical prospecting and drilling. The results indicate that karst development is mainly controlled by formation lithology, topography and neoteetonics. The surface karst morphyology is multiple, and the underground karst cave and grike are development. The concrete development features are showed as below:(1)The surface karst becomes stronger from hill to valley, and the karst development depth is changed from several meters to hundred meters; the surface large karst morphology such as depression, doline etc.occur in the band distribution horizontally; depression and sinkhole are well developed at the intersection of valleys. (2)The caves and karst pipelines have four levels vertically, the elevation is 150~170m、220~250m and 310m respectively. At the same time, a mount of covered cave and karst pipelines are found in the Shujiacao valley. On the research above, the authors point out that stability of cave roof under bridge pile, covered karst collapse and different settlement of subgrade is the main engineering geological problems which have to take corresponding measures in the process of highway construction.
In the lower of Shennong river, it is widely covered by carbonatite with strong karstification, which has important influence on the construction of the Yiba highway. This paper takes Shujiacao area for example, researches on the karst development feature by in-site investigation and the data of geophysical prospecting and drilling. The results indicate that karst development is mainly controlled by formation lithology, topography and neoteetonics. The surface karst morphyology is multiple, and the underground karst cave and grike are development. The concrete development features are showed as below:(1)The surface karst becomes stronger from hill to valley, and the karst development depth is changed from several meters to hundred meters; the surface large karst morphology such as depression, doline etc.occur in the band distribution horizontally; depression and sinkhole are well developed at the intersection of valleys. (2)The caves and karst pipelines have four levels vertically, the elevation is 150~170m、220~250m and 310m respectively. At the same time, a mount of covered cave and karst pipelines are found in the Shujiacao valley. On the research above, the authors point out that stability of cave roof under bridge pile, covered karst collapse and different settlement of subgrade is the main engineering geological problems which have to take corresponding measures in the process of highway construction.
2017, 25(s1): 35-40.
There were 33km lines in the karst development area of the Guang-Qing Expressway expansion project. There have been many karst collapses during the construction of the area. The formation of karst collapse is due to the stress of rock and soil greater than the resistance to collapse. Different types of collapsing stress may cause diverse mechanical effects, which constitute varieties of collapsing modes. Based on the analysis of climate, topography, geological structure, hydrogeological conditions of the Guang-Qing highway and so on, the formation mechanism and catastrophe mode of karst collapses during construction are discussed. It is pointed out that rainfall and construction technology are the main inducing factors for karst collapse. The main catastrophe modes are analyzed in detail during the construction process, including the submerged model, the vibration mode and the load mode. The methods of preventing and dealing with these collapse modes are proposed. The analysis results can provide a reference for the prevention and treatment of collapse in karst areas.
There were 33km lines in the karst development area of the Guang-Qing Expressway expansion project. There have been many karst collapses during the construction of the area. The formation of karst collapse is due to the stress of rock and soil greater than the resistance to collapse. Different types of collapsing stress may cause diverse mechanical effects, which constitute varieties of collapsing modes. Based on the analysis of climate, topography, geological structure, hydrogeological conditions of the Guang-Qing highway and so on, the formation mechanism and catastrophe mode of karst collapses during construction are discussed. It is pointed out that rainfall and construction technology are the main inducing factors for karst collapse. The main catastrophe modes are analyzed in detail during the construction process, including the submerged model, the vibration mode and the load mode. The methods of preventing and dealing with these collapse modes are proposed. The analysis results can provide a reference for the prevention and treatment of collapse in karst areas.
2017, 25(s1): 41-47.
The Loess Plateau is the core region of the Belt and Road strategy implementation in China. In the recent years, more and more traffic, pipelines, water conservancy and other infrastructure construction are carried out in this region, and the rapid period development of long-distance pipeline construction has been come. In this paper, interpretation keys of the engineering geological conditions such as topography, geological structure and geological disasters were established by use of LANDSAT OLI/TIRS 8,GF-1 and QuickBird data in the survey of Pipeline Engineering Geology in Loess Plateau, meanwhile, use of UAV remote sensing in key section. And, the application of multilevel remote sensing in pipeline engineering geology survey was studied from four levels, low, medium, high and ultra-high resolution. The research results show that the multilevel remote sensing will play an important role in survey of engineering geology in the Belt and Road region due to advantages of rapidity, high efficiency and economy. The research results show that the multilevel remote sensing will play an important role in survey of engineering geology in the Belt and Road region due to advantages of rapidity, high efficiency and economy.
The Loess Plateau is the core region of the Belt and Road strategy implementation in China. In the recent years, more and more traffic, pipelines, water conservancy and other infrastructure construction are carried out in this region, and the rapid period development of long-distance pipeline construction has been come. In this paper, interpretation keys of the engineering geological conditions such as topography, geological structure and geological disasters were established by use of LANDSAT OLI/TIRS 8,GF-1 and QuickBird data in the survey of Pipeline Engineering Geology in Loess Plateau, meanwhile, use of UAV remote sensing in key section. And, the application of multilevel remote sensing in pipeline engineering geology survey was studied from four levels, low, medium, high and ultra-high resolution. The research results show that the multilevel remote sensing will play an important role in survey of engineering geology in the Belt and Road region due to advantages of rapidity, high efficiency and economy. The research results show that the multilevel remote sensing will play an important role in survey of engineering geology in the Belt and Road region due to advantages of rapidity, high efficiency and economy.
2017, 25(s1): 48-54.
To date, landslide risk assessment along linear projects is limited. Evaluation indexes based on hazard inducing environment, trigger conditions and disaster characteristics of landslide disaster and the property characteristics, exposure and resilience of disaster body are selected in this study. The evaluation method of contribution weight approach is applied to the risk quantitative evaluation of Lumao line experimentally. Risk grading and mapping are done in GIS system by natural breaks method and the acceptable risk level of the transmission line landslide disaster is quantitative analyzed. It is showed that lines of high vulnerability are lines of N5~N8,N30~N34. To prevent damage of those transmission lines, corresponding protection measures to geological hazards should be built. This method can provide technical support for risk management and selection of significant linear engineering affected by the landslide disaster.
To date, landslide risk assessment along linear projects is limited. Evaluation indexes based on hazard inducing environment, trigger conditions and disaster characteristics of landslide disaster and the property characteristics, exposure and resilience of disaster body are selected in this study. The evaluation method of contribution weight approach is applied to the risk quantitative evaluation of Lumao line experimentally. Risk grading and mapping are done in GIS system by natural breaks method and the acceptable risk level of the transmission line landslide disaster is quantitative analyzed. It is showed that lines of high vulnerability are lines of N5~N8,N30~N34. To prevent damage of those transmission lines, corresponding protection measures to geological hazards should be built. This method can provide technical support for risk management and selection of significant linear engineering affected by the landslide disaster.
2017, 25(s1): 55-59.
The depth of excavation in standard section is about 16.49m, and the pit depth of the east and west ends of the well location is about 17.72m and 18.21m respectively, the main soil layer on the foundation pit is cohesive soil and silty clay in Lucheng Railway Station of Changzhou Metro 2. Bored pile with bracing retaining and protection plan was employed in subway station deep foundation excavation project through the optimization design and demonstration, for realizing the design ideas of feasible technology, economical, practical and safe, environment-friendly and fuel-efficient. Three-axis mixing pile(high pressure jet grouting pile is used under the high voltage line) waterproof wall is adopted outside the foundation, and the tube well precipitation(drainage well, decompression well) is utilized inside the foundation. Compared with the diaphragm wall(internal support),the retaining structure of bored pile can reduce the cost of construction by about 30%under the same support condition. The engineering practice proves that the design scheme of the support project has reached the expected goal.
The depth of excavation in standard section is about 16.49m, and the pit depth of the east and west ends of the well location is about 17.72m and 18.21m respectively, the main soil layer on the foundation pit is cohesive soil and silty clay in Lucheng Railway Station of Changzhou Metro 2. Bored pile with bracing retaining and protection plan was employed in subway station deep foundation excavation project through the optimization design and demonstration, for realizing the design ideas of feasible technology, economical, practical and safe, environment-friendly and fuel-efficient. Three-axis mixing pile(high pressure jet grouting pile is used under the high voltage line) waterproof wall is adopted outside the foundation, and the tube well precipitation(drainage well, decompression well) is utilized inside the foundation. Compared with the diaphragm wall(internal support),the retaining structure of bored pile can reduce the cost of construction by about 30%under the same support condition. The engineering practice proves that the design scheme of the support project has reached the expected goal.
STUDY OF ACCELEROMETER DATA FUSION IN MONITORING OF GROUND SUBSIDENCE INDUCED BY TUNNEL CONSTRUCTION
2017, 25(s1): 60-67.
Monitoring and controlling of tunneling caused ground subsidence is a key issue related to construction safety. Instead of real-time monitoring, manually measurement using total station or leveling instrument is usually conducted at regular intervals. With the rapid development of wireless sensor networks and microelectro mechanical systems, geological engineers are able to carry out a real-time wireless monitoring of ground subsidence through sensor nodes deployed on the ground. In this paper, we provide a study of accelerometer data fusion in the use of ground settlement monitoring based on surface measurements during shield tunneling. Initially, two sets of sensor nodes were placed at the surface above the excavated tunnel; after obtaining the raw data, the normal vectors of the sensors were firstly derived with the help of rotation matrices, then the dip angles over time were obtained from the projection of normal vectors in the longitudinal section; finally, a centralized Kalman filter was applied to estimate the tilt angles of the sensor nodes based on the data from two respective sets of accelerometers. Using this method, the absolute ground settlement can be achieved via a distributed deployment of sensor nodes.
Monitoring and controlling of tunneling caused ground subsidence is a key issue related to construction safety. Instead of real-time monitoring, manually measurement using total station or leveling instrument is usually conducted at regular intervals. With the rapid development of wireless sensor networks and microelectro mechanical systems, geological engineers are able to carry out a real-time wireless monitoring of ground subsidence through sensor nodes deployed on the ground. In this paper, we provide a study of accelerometer data fusion in the use of ground settlement monitoring based on surface measurements during shield tunneling. Initially, two sets of sensor nodes were placed at the surface above the excavated tunnel; after obtaining the raw data, the normal vectors of the sensors were firstly derived with the help of rotation matrices, then the dip angles over time were obtained from the projection of normal vectors in the longitudinal section; finally, a centralized Kalman filter was applied to estimate the tilt angles of the sensor nodes based on the data from two respective sets of accelerometers. Using this method, the absolute ground settlement can be achieved via a distributed deployment of sensor nodes.
2017, 25(s1): 68-71.
On account of the complexity of the karst growth, it is difficult to predict water burst during tunnel construction. By methods of investigation and observation, this article take the Sanquan tunnel for example, to find the distribution, types, connectivity, and response after rainfall of water burst. The tunnel water burst range on K7+047 to K7+0130. The water burst is increased in the direction of rock tendency. Water burst mainly appear in the direction of underground river origin. Water burst points are connected. Under the influence of rainfall, rock fracture water burst vary in small amplitude, and karst pipe water burst vary sharply.
On account of the complexity of the karst growth, it is difficult to predict water burst during tunnel construction. By methods of investigation and observation, this article take the Sanquan tunnel for example, to find the distribution, types, connectivity, and response after rainfall of water burst. The tunnel water burst range on K7+047 to K7+0130. The water burst is increased in the direction of rock tendency. Water burst mainly appear in the direction of underground river origin. Water burst points are connected. Under the influence of rainfall, rock fracture water burst vary in small amplitude, and karst pipe water burst vary sharply.
2017, 25(s1): 72-77.
The problem of grouting to stop water and reinforce under the condition of dynamic water pressure is an important problem of groundwater control of shallow tunnel with fewer experiences in the aspects of ratio of slurry, grouting parameters of design and construction. Taking the underground water control engineering of a subway connecting passage as the background, combined with the current situation of complex geological conditions, high artesian head, and phenomenon of water inrush, construction technology of joint control scheme of WSS double fluid grouting under the condition of high pressure water head was presented, based on the idea of grouting, pressure decreases, and the control effect of the technology was studied by the method of scene detection and land subsidence monitoring. The results show that the joint control scheme has gained a good effect of grouting and reinforce under the condition of dynamic water pressure, and can ensures that the underground tunnel grouting process smoothly, achieve good groundwater treatment effect and ensure underground tunnel deformation control in a reasonable range.
The problem of grouting to stop water and reinforce under the condition of dynamic water pressure is an important problem of groundwater control of shallow tunnel with fewer experiences in the aspects of ratio of slurry, grouting parameters of design and construction. Taking the underground water control engineering of a subway connecting passage as the background, combined with the current situation of complex geological conditions, high artesian head, and phenomenon of water inrush, construction technology of joint control scheme of WSS double fluid grouting under the condition of high pressure water head was presented, based on the idea of grouting, pressure decreases, and the control effect of the technology was studied by the method of scene detection and land subsidence monitoring. The results show that the joint control scheme has gained a good effect of grouting and reinforce under the condition of dynamic water pressure, and can ensures that the underground tunnel grouting process smoothly, achieve good groundwater treatment effect and ensure underground tunnel deformation control in a reasonable range.
2017, 25(s1): 78-89.
With the help of digital photographic measurement technology, the deformation and failure character and dynamical evolution process of the overlying rock strata of NO.2 open-pit of Jingning phosphorite mine of Yunnan Phosphate Chemical Group Co., LTD., was studied during transformation from open-pit to underground mining of sublevel caving method. And we carried similar material simulating experiment to do target researching on these issues. In the meantime, the thickness effects of the deformation and failure character of the overmation and failure character of the overlying rock strata was also investigated. The results showed that:(1)As the stope spatial range is increased, the range and extent of tlying rock strata increases. And the evolution process of mining deformation of the overlying rock strata could be divided into three stages, which contained the stage of roof caving in originally small and local scale, linear continuous increase stage and the whole nonlinear violent collapse stage. (2)After the ore body thickness increasing from 6.80meters to 11.40meters, the mining influence area of overlying rock strata, the extent of deformation and failure and caving angle all extend, and the geometric shape of settlement curve changed from approximate ladle-shaped type to asymmetric half-bow shape. (3)After the full recovery stage, the evolution process of mining deformation and failure of the overlying rock strata appear obviously paroxysmal and timing effects. The conclusions provide a theoretical reference for ground pressure management in mine transition from open pit to underground mining.
With the help of digital photographic measurement technology, the deformation and failure character and dynamical evolution process of the overlying rock strata of NO.2 open-pit of Jingning phosphorite mine of Yunnan Phosphate Chemical Group Co., LTD., was studied during transformation from open-pit to underground mining of sublevel caving method. And we carried similar material simulating experiment to do target researching on these issues. In the meantime, the thickness effects of the deformation and failure character of the overmation and failure character of the overlying rock strata was also investigated. The results showed that:(1)As the stope spatial range is increased, the range and extent of tlying rock strata increases. And the evolution process of mining deformation of the overlying rock strata could be divided into three stages, which contained the stage of roof caving in originally small and local scale, linear continuous increase stage and the whole nonlinear violent collapse stage. (2)After the ore body thickness increasing from 6.80meters to 11.40meters, the mining influence area of overlying rock strata, the extent of deformation and failure and caving angle all extend, and the geometric shape of settlement curve changed from approximate ladle-shaped type to asymmetric half-bow shape. (3)After the full recovery stage, the evolution process of mining deformation and failure of the overlying rock strata appear obviously paroxysmal and timing effects. The conclusions provide a theoretical reference for ground pressure management in mine transition from open pit to underground mining.
2017, 25(s1): 90-96.
Shield tunnelling is more and more popular in the modern underground projects because of its high efficiency, and its geological condition is more and more complicated. As a special geological environment, dense sand has a direct impact on shield tunnelling. But so far, the study on the characteristics of dense sand has not yet reached the mature stage. In this paper, portable digital microscope was employed to capture images of undisturbed sand which comes from Sutong GIL Utility Tunnel Engineering; Adobe Photoshop splicing, the spliced image were subsequently converted into binary picture to produce contour boundary for particle shape; finally image-Pro plus was used to count and analyze particle shape parameters; the test results and the Sutong GIL Utility Tunnel Engineering survey results were compared. It is concluded that the method can be used as an effective means to accomplish the dense sand particle shape quantification and the dense sand has a long axis distribution in the space, which has a good correlation with the shape parameters of the particles. The results of the study have reference value for the study of particle shape, and have guiding significance for the construction of shield tunnel.
Shield tunnelling is more and more popular in the modern underground projects because of its high efficiency, and its geological condition is more and more complicated. As a special geological environment, dense sand has a direct impact on shield tunnelling. But so far, the study on the characteristics of dense sand has not yet reached the mature stage. In this paper, portable digital microscope was employed to capture images of undisturbed sand which comes from Sutong GIL Utility Tunnel Engineering; Adobe Photoshop splicing, the spliced image were subsequently converted into binary picture to produce contour boundary for particle shape; finally image-Pro plus was used to count and analyze particle shape parameters; the test results and the Sutong GIL Utility Tunnel Engineering survey results were compared. It is concluded that the method can be used as an effective means to accomplish the dense sand particle shape quantification and the dense sand has a long axis distribution in the space, which has a good correlation with the shape parameters of the particles. The results of the study have reference value for the study of particle shape, and have guiding significance for the construction of shield tunnel.
2017, 25(s1): 97-102.
In recent years, as a new type of renewable energy, geothermal resources obtained significant environmental, social and economic benefit. Through the means of targeted data collection, high-precision gravity survey, well correlation analysis, and scientific construction organization,Tongre-19 and injection geothermal well had been successfully completed. And the mode of combination of exploitation and injection was employed in this project. The depth of the Tongre-19 geothermal well is 2370.00m, the well yield is 603m3d-1,the temperature of water is 45℃.With these conditions, the well has been evaluated as high-quality geothermal well. For the important geographical position, being adjacent to Beijing Sub-center, this project can provide important data and present important references for geothermal resources research in this area.
In recent years, as a new type of renewable energy, geothermal resources obtained significant environmental, social and economic benefit. Through the means of targeted data collection, high-precision gravity survey, well correlation analysis, and scientific construction organization,Tongre-19 and injection geothermal well had been successfully completed. And the mode of combination of exploitation and injection was employed in this project. The depth of the Tongre-19 geothermal well is 2370.00m, the well yield is 603m3d-1,the temperature of water is 45℃.With these conditions, the well has been evaluated as high-quality geothermal well. For the important geographical position, being adjacent to Beijing Sub-center, this project can provide important data and present important references for geothermal resources research in this area.
2017, 25(s1): 103-107.
According to investigation of permanent roadways, the Y-shape intersection is main form of No.2mine area in Jinchuan mine. For roadway intersection, many factors have influenced stability of roadway, sequence excavation is fallen into this category. A finite element software is utilized to simulate Y-shape roadway intersection in No.2mine area in Jinchuan, and analyzed stress and displacement influenced by different excavation sequences. There are two types of excavation sequences:type one:main roadway-branch roadway; type two:main roadway-branch roadway-main roadway. The results showed as follows:the displacement of intersection roadway by type-two sequence is bigger than displacement intersection roadway by type-one sequence. Branch roadway excavation leaded to value difference in both sides of roadway. As displacement increased, the stresses of roadway have been offset. This features provided some reference for roadway support. Finally, Y-shaped intersection excavation should first choose type-one sequence for stable. Appropriate support should be used in roadway intersection excavated by type-two.
According to investigation of permanent roadways, the Y-shape intersection is main form of No.2mine area in Jinchuan mine. For roadway intersection, many factors have influenced stability of roadway, sequence excavation is fallen into this category. A finite element software is utilized to simulate Y-shape roadway intersection in No.2mine area in Jinchuan, and analyzed stress and displacement influenced by different excavation sequences. There are two types of excavation sequences:type one:main roadway-branch roadway; type two:main roadway-branch roadway-main roadway. The results showed as follows:the displacement of intersection roadway by type-two sequence is bigger than displacement intersection roadway by type-one sequence. Branch roadway excavation leaded to value difference in both sides of roadway. As displacement increased, the stresses of roadway have been offset. This features provided some reference for roadway support. Finally, Y-shaped intersection excavation should first choose type-one sequence for stable. Appropriate support should be used in roadway intersection excavated by type-two.
2017, 25(s1): 108-114.
Jiaodong Peninsula locates at the southeastern edge of north China craton with a complex geological structure. It is an important producing area of gold in China. To reveal the metallogenic regularity in depth, Shandong Gold Geology and Mineral Resources Co.applied the small-caliber diamond wireline core drilling to prospect the deep gold deposit of Sanshandao. Shengli Logging Company of Engineering Company also conducted the digitizing geophysical well logging in 4000m depth by a small-caliber logs( 60mm) developed its own that made the new record in the field of ultra-depth drilling using small-caliber logs. This study applied the model founded by other researchers to calculate the parameters of Rock mechanics and In-Situ stress by using difference time of S-wave which is predicted by combining the curve of the difference time of p-wave and density. The results showed the minimum horizontal stress was 0.02MPam-1 that calculated from geophysical parametric inversion. The gradient of maximum horizontal stress ranges from 0.024MPam-1 to 0.03MPam-1 and the gradient of vertical stress keeps 0.027MPam-1. The magnitude of in-situ stress in descending order is vertical stress, maximum horizontal stress, and minimum horizontal stress. The type of in-situ stress belongs to normal fault. Finally, this result showed the significance to mining operation in depth. The results could be utilized to guide design of deep mine excavation in the future.
Jiaodong Peninsula locates at the southeastern edge of north China craton with a complex geological structure. It is an important producing area of gold in China. To reveal the metallogenic regularity in depth, Shandong Gold Geology and Mineral Resources Co.applied the small-caliber diamond wireline core drilling to prospect the deep gold deposit of Sanshandao. Shengli Logging Company of Engineering Company also conducted the digitizing geophysical well logging in 4000m depth by a small-caliber logs( 60mm) developed its own that made the new record in the field of ultra-depth drilling using small-caliber logs. This study applied the model founded by other researchers to calculate the parameters of Rock mechanics and In-Situ stress by using difference time of S-wave which is predicted by combining the curve of the difference time of p-wave and density. The results showed the minimum horizontal stress was 0.02MPam-1 that calculated from geophysical parametric inversion. The gradient of maximum horizontal stress ranges from 0.024MPam-1 to 0.03MPam-1 and the gradient of vertical stress keeps 0.027MPam-1. The magnitude of in-situ stress in descending order is vertical stress, maximum horizontal stress, and minimum horizontal stress. The type of in-situ stress belongs to normal fault. Finally, this result showed the significance to mining operation in depth. The results could be utilized to guide design of deep mine excavation in the future.
2017, 25(s1): 115-118.
A large number of experimental data indicators that there is a good correlation between the physico-mechanical property indexes of rock and soil. On-site and laboratory tests in a nuclear power plant are performed to investigate the space distribution and correlation of dynamic parameters and static parameters. Also carry out some statistics and analysis on the engineering property indexes of the tertiary sandstone. Regression analysis indicates that there exists good correlation between natural uniaxial compressive strength and natural density, elastic modulus, pressure meter test parameters and shear wave velocity. Correlation equations are established to make it useful on geotechnical engineering designing and construction.
A large number of experimental data indicators that there is a good correlation between the physico-mechanical property indexes of rock and soil. On-site and laboratory tests in a nuclear power plant are performed to investigate the space distribution and correlation of dynamic parameters and static parameters. Also carry out some statistics and analysis on the engineering property indexes of the tertiary sandstone. Regression analysis indicates that there exists good correlation between natural uniaxial compressive strength and natural density, elastic modulus, pressure meter test parameters and shear wave velocity. Correlation equations are established to make it useful on geotechnical engineering designing and construction.
2017, 25(s1): 119-122.
Red layer pumped well in Chongqing is drilled in the red strata area of Penglai Formation to Zhenzhuchong Formation of Jurassic. It solved the difficulties of getting water for the people that lived in Chongqing red layer area. But the new problem of use and maintenance of pumped well is coming out after that. The function of some pumped well is gradually degradation. Through the investigation and analysis of pumped well in Chongqing red layer area, this paper found that after two years of the pumped well built, the function of some pumped wells is going to degrade. Such as with heavy sand and silt at the bottom of well, the water volume decreased, turbid water, the protective pip destroyed, water level falls and the well wall collapse and jam the well, et al. Growth over time, the function of pumped well degrades sharply. Taking effective well washing and maintenance measures can increase the water volume and improve the water quality. It can promote the using function.
Red layer pumped well in Chongqing is drilled in the red strata area of Penglai Formation to Zhenzhuchong Formation of Jurassic. It solved the difficulties of getting water for the people that lived in Chongqing red layer area. But the new problem of use and maintenance of pumped well is coming out after that. The function of some pumped well is gradually degradation. Through the investigation and analysis of pumped well in Chongqing red layer area, this paper found that after two years of the pumped well built, the function of some pumped wells is going to degrade. Such as with heavy sand and silt at the bottom of well, the water volume decreased, turbid water, the protective pip destroyed, water level falls and the well wall collapse and jam the well, et al. Growth over time, the function of pumped well degrades sharply. Taking effective well washing and maintenance measures can increase the water volume and improve the water quality. It can promote the using function.
2017, 25(s1): 123-128.
A power plant in basalt complex geological conditions, exploration and development of the right to expose the bed on the right bank of confined water. Research shows that the fractured basalt aquifer system with the inhomogeneity, anisotropy and multi-level characteristics. In this paper, the method of evaluating the permeability of rock mass is given based on the fracture characteristics and permeability coefficient. According to the burial conditions, the chemical composition of the water can be divided into upper and lower water pressure of confined water, respectively. The distribution characteristics of confined water level and discharge, the dynamic characteristics of confined water, water chemistry characteristics, storage environment characteristics, supply, runoff and discharge characteristics are discussed, analyzed the influence of confined water on the dam, take targeted treatment measures based on the analysis results, achieved good results.
A power plant in basalt complex geological conditions, exploration and development of the right to expose the bed on the right bank of confined water. Research shows that the fractured basalt aquifer system with the inhomogeneity, anisotropy and multi-level characteristics. In this paper, the method of evaluating the permeability of rock mass is given based on the fracture characteristics and permeability coefficient. According to the burial conditions, the chemical composition of the water can be divided into upper and lower water pressure of confined water, respectively. The distribution characteristics of confined water level and discharge, the dynamic characteristics of confined water, water chemistry characteristics, storage environment characteristics, supply, runoff and discharge characteristics are discussed, analyzed the influence of confined water on the dam, take targeted treatment measures based on the analysis results, achieved good results.
2017, 25(s1): 129-134.
Crown land is a high gravity dam hydroelectric complex geological conditions, rock dam reasonably accurate evaluation of the quality and effective treatment of defects in the dam's safety is essential. Based on the sketch and the actual excavation of exposed geological conditions, through the geological documentation of qualitative evaluation and quantitative assessment of the gravity geophysical detection of rock foundation excavation comprehensive evaluation results show that rock excavation to expose essentially the same geology and previous surveys, the overall rock mass dam to meet the requirements. It has certain guiding significance for the rock mass evaluation of gravity dam foundation in the future.
Crown land is a high gravity dam hydroelectric complex geological conditions, rock dam reasonably accurate evaluation of the quality and effective treatment of defects in the dam's safety is essential. Based on the sketch and the actual excavation of exposed geological conditions, through the geological documentation of qualitative evaluation and quantitative assessment of the gravity geophysical detection of rock foundation excavation comprehensive evaluation results show that rock excavation to expose essentially the same geology and previous surveys, the overall rock mass dam to meet the requirements. It has certain guiding significance for the rock mass evaluation of gravity dam foundation in the future.
2017, 25(s1): 135-139.
In this article, through field sampling of a practical project in Beijing, determine the regional soil hardening model parameters through indoor triaxial test and consolidation test. Such as the strength parameters and stiffness parameters are greater than survey report provides. The finite element analysis software Midas GTS was used to simulate the excavation process of the foundation pit in modified Mohr Coulomb model, and compared with the measured data to verify the applicability of the model parameters. The strength parameters and the stiffness parameters of the soil determined by indoor triaxial test and consolidation test are more consistent with the mechanical properties of the undisturbed soil. These parameters can be used to predict the deformation of foundation pit and the force of supporting structure more reasonably. It provides a new reference for optimization of geotechnical engineering design.
In this article, through field sampling of a practical project in Beijing, determine the regional soil hardening model parameters through indoor triaxial test and consolidation test. Such as the strength parameters and stiffness parameters are greater than survey report provides. The finite element analysis software Midas GTS was used to simulate the excavation process of the foundation pit in modified Mohr Coulomb model, and compared with the measured data to verify the applicability of the model parameters. The strength parameters and the stiffness parameters of the soil determined by indoor triaxial test and consolidation test are more consistent with the mechanical properties of the undisturbed soil. These parameters can be used to predict the deformation of foundation pit and the force of supporting structure more reasonably. It provides a new reference for optimization of geotechnical engineering design.
2017, 25(s1): 140-146.
The distinguishing grain size of coarse and fine particles is an important discriminant indicator for the seepage deformation type of cohesionless coarse grain soil. As the determination methods and the values are not unified, statistical analysis on seepage deformation testing results were taken with 62 sand samples from 7 projects to verify the suitability of different methods. The results show that the coincidence rate of the discrimination result and the testing result of seepage deformation is 93.55%when 2mm is used as the distinguishing grain size instead of d70d10, which is much higher than 51.61%. Thus, 2mm is recommended as the distinguishing grain size of coarse and fine particles for the non-uniform continuously graded sand.
The distinguishing grain size of coarse and fine particles is an important discriminant indicator for the seepage deformation type of cohesionless coarse grain soil. As the determination methods and the values are not unified, statistical analysis on seepage deformation testing results were taken with 62 sand samples from 7 projects to verify the suitability of different methods. The results show that the coincidence rate of the discrimination result and the testing result of seepage deformation is 93.55%when 2mm is used as the distinguishing grain size instead of d70d10, which is much higher than 51.61%. Thus, 2mm is recommended as the distinguishing grain size of coarse and fine particles for the non-uniform continuously graded sand.
2017, 25(s1): 147-152.
The medium-coarse sand has good physical and mechanical properties and extensive engineering applications. In order to further study on medium-coarse sand permeability and permeability deformation, statistical analysis on the type and parameter of permeability deformation is carried out base on the testing data of 48 samples taken from 6 projects. The results indicate that the permeability deformation types of all the samples are soil flow with the critical gradient value of 0.6~1.2,failure gradient 0.9~1.7, and permeability coefficient 2.010-2cms-1~2.010-4cms-1,meanwhile, the critical gradient and failture gradient have good correlativity.
The medium-coarse sand has good physical and mechanical properties and extensive engineering applications. In order to further study on medium-coarse sand permeability and permeability deformation, statistical analysis on the type and parameter of permeability deformation is carried out base on the testing data of 48 samples taken from 6 projects. The results indicate that the permeability deformation types of all the samples are soil flow with the critical gradient value of 0.6~1.2,failure gradient 0.9~1.7, and permeability coefficient 2.010-2cms-1~2.010-4cms-1,meanwhile, the critical gradient and failture gradient have good correlativity.
2017, 25(s1): 153-157.
Fine grains in loose soils can be erosion and re-deposition by seepage which can change the grain series and micro-structure of the soils. Accordingly the macro properties such as strength and modulus can be changes. In this paper test based on nuclear magnetic resonance instrument observation and simulation based on pore network model were carried out to analyze the effects of the migration of fine grains on the soils macro-properties. It is shown that fine grains are eroded and migrated along depth with pore water flow and most of them are assembled at the middle of the soil layer, which causes the porosity at the diddle layer is obvious smaller than that of the upper and lower layers. During seepage, pore water cannot flows through the whole area. In fact, at the upper, lower and middle layers, there all exist small or large areas which are not filled by water. Simulation shows that the area of the middle layer spread by water and the flow channels are the least, therefore under the same flow rate the pore water pressure is higher, so the changes of the strength and stiffness in the middle layer are the largest.
Fine grains in loose soils can be erosion and re-deposition by seepage which can change the grain series and micro-structure of the soils. Accordingly the macro properties such as strength and modulus can be changes. In this paper test based on nuclear magnetic resonance instrument observation and simulation based on pore network model were carried out to analyze the effects of the migration of fine grains on the soils macro-properties. It is shown that fine grains are eroded and migrated along depth with pore water flow and most of them are assembled at the middle of the soil layer, which causes the porosity at the diddle layer is obvious smaller than that of the upper and lower layers. During seepage, pore water cannot flows through the whole area. In fact, at the upper, lower and middle layers, there all exist small or large areas which are not filled by water. Simulation shows that the area of the middle layer spread by water and the flow channels are the least, therefore under the same flow rate the pore water pressure is higher, so the changes of the strength and stiffness in the middle layer are the largest.
2017, 25(s1): 158-163.
In tunnel excavation, there exist the water inrush and mud burst disaster-causing structures which are closed to the excavated surface or are outside of the contour lines. Due to the thickness of water-resisting and mud-resisting rock-soil plate, located in the water inrush and mud burst disaster-causing structures between the excavated surface and the front of the excavated surface or between the excavated contour line and outside of the excavated contour line, is less than the minimum safety thickness of the rock-soil plate, and under the stress of the underground water of the water inrush disaster-causing structure or the stress of the clay of mud burst disaster-causing structure, water-resisting and mud-resisting rock-soil plate is instable, water inrush or mud burst disasters are triggered in tunnel excavation. Based on the cases of water inrush and mud burst disasters in decade, this paper summarizes and proposes the structure types and the patterns of the water-resisting and mud-resisting rock-soil plate causing water inrush and mud burst disasters. It also analyses five types of the water-resisting and mud-resisting rock-soil plates:the various sizes of broken rock blocks with or without clay(rock particles and sand-cobbles),the fractured rocks filled with or without fractured clay, the clay or fault gouge, the complete rock, and the water-resisting and mud-resisting rock-soil initial support plate. Meanwhile, on the fundament of those five types of the water-resisting and mud-resisting rock-soil plates, this paper presents five failure patterns:seepage(collapsibility) failure, shear failure, softening and burst failure, cracking and burst failure, and bending failure. It also analyses the interrelations between the structure types and the patterns of the water-resisting and mud-resisting rock-soil plate.
In tunnel excavation, there exist the water inrush and mud burst disaster-causing structures which are closed to the excavated surface or are outside of the contour lines. Due to the thickness of water-resisting and mud-resisting rock-soil plate, located in the water inrush and mud burst disaster-causing structures between the excavated surface and the front of the excavated surface or between the excavated contour line and outside of the excavated contour line, is less than the minimum safety thickness of the rock-soil plate, and under the stress of the underground water of the water inrush disaster-causing structure or the stress of the clay of mud burst disaster-causing structure, water-resisting and mud-resisting rock-soil plate is instable, water inrush or mud burst disasters are triggered in tunnel excavation. Based on the cases of water inrush and mud burst disasters in decade, this paper summarizes and proposes the structure types and the patterns of the water-resisting and mud-resisting rock-soil plate causing water inrush and mud burst disasters. It also analyses five types of the water-resisting and mud-resisting rock-soil plates:the various sizes of broken rock blocks with or without clay(rock particles and sand-cobbles),the fractured rocks filled with or without fractured clay, the clay or fault gouge, the complete rock, and the water-resisting and mud-resisting rock-soil initial support plate. Meanwhile, on the fundament of those five types of the water-resisting and mud-resisting rock-soil plates, this paper presents five failure patterns:seepage(collapsibility) failure, shear failure, softening and burst failure, cracking and burst failure, and bending failure. It also analyses the interrelations between the structure types and the patterns of the water-resisting and mud-resisting rock-soil plate.
2017, 25(s1): 164-169.
Changchun subway tunnel excavated through the strong weathered mudstone layer, strong weather mudstone belongs to the weak rock, it has rheological properties, and it has very significant impact on the stability of the subway tunnel and other underground structure. The study on the creep mechanics characteristics of weak rock mass can provide the theoretical basis for the surrounding rock of the subway tunnel and the design of the underground structure. The strong weathered mudstone sampling was carried out in the excavation surface of the subway tunnel in the study area. Direct shear creep tests were carried out the creep characteristics of strong weathered mudstone were obtained. The long-term strength of mudstone was obtained by different methods:transition creep law, the first inflection point method and isochronous curves method, and the results were compared and analyzed. The results show that the long-term strength of mudstone is obviously reduced compared with the instantaneous strength,c/c is 20%~40%, and tan/tan is 60%~70%.Therefore, it is necessary to use the long-term strength index as a reference in the actual design of rock engineering.
Changchun subway tunnel excavated through the strong weathered mudstone layer, strong weather mudstone belongs to the weak rock, it has rheological properties, and it has very significant impact on the stability of the subway tunnel and other underground structure. The study on the creep mechanics characteristics of weak rock mass can provide the theoretical basis for the surrounding rock of the subway tunnel and the design of the underground structure. The strong weathered mudstone sampling was carried out in the excavation surface of the subway tunnel in the study area. Direct shear creep tests were carried out the creep characteristics of strong weathered mudstone were obtained. The long-term strength of mudstone was obtained by different methods:transition creep law, the first inflection point method and isochronous curves method, and the results were compared and analyzed. The results show that the long-term strength of mudstone is obviously reduced compared with the instantaneous strength,c/c is 20%~40%, and tan/tan is 60%~70%.Therefore, it is necessary to use the long-term strength index as a reference in the actual design of rock engineering.
2017, 25(s1): 170-177.
The influence of blasting vibration on the interaction between the rock pile and the embedded rock mass is obvious, which is an important factor affecting the failure of the anti-slide pile. According to the prototype of a landslide in Yueyang, Hunan Province, the dynamic response of anti-slide pile and embedded rock mass with blasting vibration is established by FLAC3D.The results show that under the condition of the width and height of the fixed bedrock and the depth of the anti-slide pile, the displacement, acceleration, velocity and stress of the rock in the embedded rock are in accordance with their homogeneity under the conditions of the elevation amplification effect. However, when the wave impedance difference in the inhomogeneous rock mass is large, the acceleration response does not exactly accord with the elevation amplification effect. The displacement, acceleration and velocity curves of the embedded rock mass in the same horizontal position of the cantilever anti-slide pile are consistent and the stress is inconsistent. The pile at both ends of the moment and the shear force is small, the middle is large, and after the blasting the middle of the landslide and the trailing edge of the landslide are susceptible to torsional failure, it should strengthen the anti-slide pile in the bedrock and sliding body interface and landslide protection of central and trailing edge. Based on the above results, the frequency of the blasting vibration process is analyzed by MATLAB,which can be judged to be safe after blasting. The results provide a scientific basis for the design and construction of landslide.
The influence of blasting vibration on the interaction between the rock pile and the embedded rock mass is obvious, which is an important factor affecting the failure of the anti-slide pile. According to the prototype of a landslide in Yueyang, Hunan Province, the dynamic response of anti-slide pile and embedded rock mass with blasting vibration is established by FLAC3D.The results show that under the condition of the width and height of the fixed bedrock and the depth of the anti-slide pile, the displacement, acceleration, velocity and stress of the rock in the embedded rock are in accordance with their homogeneity under the conditions of the elevation amplification effect. However, when the wave impedance difference in the inhomogeneous rock mass is large, the acceleration response does not exactly accord with the elevation amplification effect. The displacement, acceleration and velocity curves of the embedded rock mass in the same horizontal position of the cantilever anti-slide pile are consistent and the stress is inconsistent. The pile at both ends of the moment and the shear force is small, the middle is large, and after the blasting the middle of the landslide and the trailing edge of the landslide are susceptible to torsional failure, it should strengthen the anti-slide pile in the bedrock and sliding body interface and landslide protection of central and trailing edge. Based on the above results, the frequency of the blasting vibration process is analyzed by MATLAB,which can be judged to be safe after blasting. The results provide a scientific basis for the design and construction of landslide.
2017, 25(s1): 178-182.
Saturation effective shear strength parameters(c',') are the basic parameters for the establishment of unsaturated soil shear strength. In order to investigate the relation between c ',' and the depositional age of loess, intact samples from L1,S1,L5 and L9,were taken from Jingyang, Shanxi Province. Using consolidated undrained(CU)test of conventional triaxial apparatus, obtain the effective shear strength parameters c' and '.Established the empirical estimation model between c' of Jingyang loess and the depositional age.
Saturation effective shear strength parameters(c',') are the basic parameters for the establishment of unsaturated soil shear strength. In order to investigate the relation between c ',' and the depositional age of loess, intact samples from L1,S1,L5 and L9,were taken from Jingyang, Shanxi Province. Using consolidated undrained(CU)test of conventional triaxial apparatus, obtain the effective shear strength parameters c' and '.Established the empirical estimation model between c' of Jingyang loess and the depositional age.
2017, 25(s1): 183-188.
Flocculation of montmorillonite colloids is influenced by the concentration and type of cations in water. NaCl, KCl, CaCl2 and MgCl2 solution were arranged into the same concentration gradient. The deposition process of montmorillonite in solution was observed. It was found that the flocculation of montmorillonite increased with the increase of the concentration of sodium and potassium ions. Calcium and magnesium ions have a critical flocculation value for montmorillonite flocculation, which is more stable than the critical concentration. It is known by the Zeta potential that it is caused by exclusive action.The law below the critical concentration is the same as that of monovalent cations. The ionic type also has an effect on the volume expansion of Montmorillonite. In the same concentration gradient, volume expansion increment ranked NaCl KCl MgCl2 CaCl2. Zeta test results show that the potential causes of flocculation and concentration of liquid suspension is cation valence state that the Montmorillonite Granules electric double layer changes.
Flocculation of montmorillonite colloids is influenced by the concentration and type of cations in water. NaCl, KCl, CaCl2 and MgCl2 solution were arranged into the same concentration gradient. The deposition process of montmorillonite in solution was observed. It was found that the flocculation of montmorillonite increased with the increase of the concentration of sodium and potassium ions. Calcium and magnesium ions have a critical flocculation value for montmorillonite flocculation, which is more stable than the critical concentration. It is known by the Zeta potential that it is caused by exclusive action.The law below the critical concentration is the same as that of monovalent cations. The ionic type also has an effect on the volume expansion of Montmorillonite. In the same concentration gradient, volume expansion increment ranked NaCl KCl MgCl2 CaCl2. Zeta test results show that the potential causes of flocculation and concentration of liquid suspension is cation valence state that the Montmorillonite Granules electric double layer changes.
2017, 25(s1): 189-193.
In order to investigate the relationship between yielding stress of structures(k) and matrix suction(),intact samples from first palaeosol(S1) and fifth loess(L5)were taken from Jingyang, Shanxi Province. The specimens were prepared as 8groups with the expected moisture content from dry to saturated respectively. Based on high-pressure consolidation test,k under different moisture content were investigated, and the wetting soil-water characteristics curves(SWCC) is measured with filter paper method. The results suggest that with the matrix suction raise,k of S1 and L5 present a S model changes. When matrix suction less than a,k is in the lowly gentle stage of the S model. When matrix suction greater than r,k is in the highly gentle stage of the S model; as well as matrix suction between them,k have a quick increase as matrix suction increases. Gravity stress is pre-consolidation pressure, and discuss the change characteristics of structures strength with matrix suction in detail.
In order to investigate the relationship between yielding stress of structures(k) and matrix suction(),intact samples from first palaeosol(S1) and fifth loess(L5)were taken from Jingyang, Shanxi Province. The specimens were prepared as 8groups with the expected moisture content from dry to saturated respectively. Based on high-pressure consolidation test,k under different moisture content were investigated, and the wetting soil-water characteristics curves(SWCC) is measured with filter paper method. The results suggest that with the matrix suction raise,k of S1 and L5 present a S model changes. When matrix suction less than a,k is in the lowly gentle stage of the S model. When matrix suction greater than r,k is in the highly gentle stage of the S model; as well as matrix suction between them,k have a quick increase as matrix suction increases. Gravity stress is pre-consolidation pressure, and discuss the change characteristics of structures strength with matrix suction in detail.
2017, 25(s1): 194-199.
Based on the research of the physical and mechanical properties of different red mud additive on red clay under various water contents, this paper show the influence and mechanism of red clay under different amount of red mud with moisture content. By scanning electron microscopy, this experiment explores the effect of soil samples on the microstructure. In the larger sense, the results show that sheer strength of soil, which is incorporatied into red mud in different ratio, increases at first and then decreases as the increase of moisture content. Compression test show that, the compressibility decreased with increasing moisture content, and the decrease amplitude increases with the growth of red mud content. From microscopic view point, the red mud additive can change the aggregation of soil particles into prothallial plate; the loose structure became denser; the reduction of pore space also makes its capacity of absorbing water is declining.
Based on the research of the physical and mechanical properties of different red mud additive on red clay under various water contents, this paper show the influence and mechanism of red clay under different amount of red mud with moisture content. By scanning electron microscopy, this experiment explores the effect of soil samples on the microstructure. In the larger sense, the results show that sheer strength of soil, which is incorporatied into red mud in different ratio, increases at first and then decreases as the increase of moisture content. Compression test show that, the compressibility decreased with increasing moisture content, and the decrease amplitude increases with the growth of red mud content. From microscopic view point, the red mud additive can change the aggregation of soil particles into prothallial plate; the loose structure became denser; the reduction of pore space also makes its capacity of absorbing water is declining.
2017, 25(s1): 200-206.
Based on practical engineering, first of all, through lab mixing proportion test and compressive strength test to determine construction scheme of cement-soil mixing pile. In addition, through the static load test to determine ultimate bearing capacity of composite foundation and strengthen the body single pile. Finally, through light dynamic penetration test, cone penetration test and core-drilling to test quality of cement-soil mixing pile, and put forward objective testing conclusion which is suitable for site conditions. This paper not only provide the basis for construction engineering design and construction, but also have practical significance for similar construction engineering.
Based on practical engineering, first of all, through lab mixing proportion test and compressive strength test to determine construction scheme of cement-soil mixing pile. In addition, through the static load test to determine ultimate bearing capacity of composite foundation and strengthen the body single pile. Finally, through light dynamic penetration test, cone penetration test and core-drilling to test quality of cement-soil mixing pile, and put forward objective testing conclusion which is suitable for site conditions. This paper not only provide the basis for construction engineering design and construction, but also have practical significance for similar construction engineering.
2017, 25(s1): 207-212.
Nano bentonite is a kind of new material, which is widely used in other industries, and has a great potential for application due to its rich resourses, low price and relatively mature production technology. This paper designed five groups of different dosage ratio of nano bentonite-red clay, and unconsolidated undrained triaxial tests under four different confining pressures were performed in each group respectively under the optimum moisture content of red clay. Finally, the effect of different content of nano bentonite on the mechanical properties of red clay was analyzed by the stress-strain curve. Thus we can get the law of shear strength and shear strength. The test results indicate that the addition of nano bentonite filled the pores of soil particles, which improved the mechanical properties of red clay. The optimum content is between 2%~3%,with the increase of the content of the red clay, the cohesion of the red clay increases at first and then decreases, while the internal friction angle of the red clay does not change. The test results indicate that the binding property of the main components of nano bentonite montmorillonite can increase the soil particle cement, and its expansive property is beneficial to filling the pore of the soil particles and its specific surface area can obviously enhance the mechanical properties of red clay.
Nano bentonite is a kind of new material, which is widely used in other industries, and has a great potential for application due to its rich resourses, low price and relatively mature production technology. This paper designed five groups of different dosage ratio of nano bentonite-red clay, and unconsolidated undrained triaxial tests under four different confining pressures were performed in each group respectively under the optimum moisture content of red clay. Finally, the effect of different content of nano bentonite on the mechanical properties of red clay was analyzed by the stress-strain curve. Thus we can get the law of shear strength and shear strength. The test results indicate that the addition of nano bentonite filled the pores of soil particles, which improved the mechanical properties of red clay. The optimum content is between 2%~3%,with the increase of the content of the red clay, the cohesion of the red clay increases at first and then decreases, while the internal friction angle of the red clay does not change. The test results indicate that the binding property of the main components of nano bentonite montmorillonite can increase the soil particle cement, and its expansive property is beneficial to filling the pore of the soil particles and its specific surface area can obviously enhance the mechanical properties of red clay.
2017, 25(s1): 213-219.
In the three axis test of sand, there is an important relationship between the evolution of pore structure and its mechanical properties and strength characteristics. This paper based on synchrotron radiation micro CT scanning, combined with three axial compression experiment of silty sand soil in Hexi area of Nanjing, using self-developed micro three axis compression observation control system online, get images of Nanjing fine sand saturated pores in the load under different confining pressure in the process of structure in real time. Three-dimensional reconstruction of scanned image by ImageJ and Avizo software, get the pore structure of space image of the sand sample in the loading process, and then simplified as pore network model, then porosity, pore shape and pore radius were used to analyze the pore structure evolution. The results show that:(1)the loose condition of Nanjing fine sand under pressure showed typical strain softening characteristics of low confining, with the increase of confining pressure began to show characteristics of strain softening-hardening; (2)in the moderate compact state, the Nanjing fine sand showed a strain softening-hardening characteristic during the triaxial compression test, that is, from the shear state to the dilatancy state. Therefore, the porosity can be used to express the relationship between the porosity of peak strength and residual strength.(3)the interconnection of small pores is the cause of the emergence of large pores, which led to the loose condition of Nanjing fine sand appeared quasi-steady state.
In the three axis test of sand, there is an important relationship between the evolution of pore structure and its mechanical properties and strength characteristics. This paper based on synchrotron radiation micro CT scanning, combined with three axial compression experiment of silty sand soil in Hexi area of Nanjing, using self-developed micro three axis compression observation control system online, get images of Nanjing fine sand saturated pores in the load under different confining pressure in the process of structure in real time. Three-dimensional reconstruction of scanned image by ImageJ and Avizo software, get the pore structure of space image of the sand sample in the loading process, and then simplified as pore network model, then porosity, pore shape and pore radius were used to analyze the pore structure evolution. The results show that:(1)the loose condition of Nanjing fine sand under pressure showed typical strain softening characteristics of low confining, with the increase of confining pressure began to show characteristics of strain softening-hardening; (2)in the moderate compact state, the Nanjing fine sand showed a strain softening-hardening characteristic during the triaxial compression test, that is, from the shear state to the dilatancy state. Therefore, the porosity can be used to express the relationship between the porosity of peak strength and residual strength.(3)the interconnection of small pores is the cause of the emergence of large pores, which led to the loose condition of Nanjing fine sand appeared quasi-steady state.
2017, 25(s1): 220-224.
General loess slope deformation and destruction associated with surface water infiltration leads to the rise of ground water level. However, in-situ observation found the loess area, surface water infiltration depth is limited, the rain moist peak within 2meters in general. Under moist peak to the moisture content of a long between the underground water level is constant, so how is the surface water recharge of groundwater, has been controversial. To this end, the paper used in Zhengning county in Gansu province Q3 loess reshape unsaturated seepage characteristics of soil column experiment was carried out. In a 4m tall glass barrel preparation of soil samples, the soil column spacing according to certain insert moisture meter probe, uniform infiltration water in the top 1000mL of water a day, measured at a given time along the moisture content of soil column section. The results found that with the supplies the extension of time, the peak down, wet moist peak after the upper soil moisture content is almost the same, when moist peak reach the bottom of the soil column, the formation of groundwater level, and the phenomenon of field observation. This shows that the surface activity with the following, above the saturated zone, while the moisture content of soil unchanged, but there is a steady unsaturated seepage, it was the only one the loess area, the groundwater recharge mode.
General loess slope deformation and destruction associated with surface water infiltration leads to the rise of ground water level. However, in-situ observation found the loess area, surface water infiltration depth is limited, the rain moist peak within 2meters in general. Under moist peak to the moisture content of a long between the underground water level is constant, so how is the surface water recharge of groundwater, has been controversial. To this end, the paper used in Zhengning county in Gansu province Q3 loess reshape unsaturated seepage characteristics of soil column experiment was carried out. In a 4m tall glass barrel preparation of soil samples, the soil column spacing according to certain insert moisture meter probe, uniform infiltration water in the top 1000mL of water a day, measured at a given time along the moisture content of soil column section. The results found that with the supplies the extension of time, the peak down, wet moist peak after the upper soil moisture content is almost the same, when moist peak reach the bottom of the soil column, the formation of groundwater level, and the phenomenon of field observation. This shows that the surface activity with the following, above the saturated zone, while the moisture content of soil unchanged, but there is a steady unsaturated seepage, it was the only one the loess area, the groundwater recharge mode.
2017, 25(s1): 225-229.
Using TFB-1 triaxial apparatus of stress and strain control, to the red clay was subjected to saturated consolidation undrained triaxial test, based on the hardening characteristics of the stress-strain curve of red clay, the constitutive model was fitted. The result of the experiment shows that the stress-strain curve of red clay shows hardening property and its strengthening inflection point appears at the strain of 0.5%~2%; strain hardening type red clay should stress and strain characteristic curve for fitting a power function model, but to strengthen the position of the inflection point is not sensitive.
Using TFB-1 triaxial apparatus of stress and strain control, to the red clay was subjected to saturated consolidation undrained triaxial test, based on the hardening characteristics of the stress-strain curve of red clay, the constitutive model was fitted. The result of the experiment shows that the stress-strain curve of red clay shows hardening property and its strengthening inflection point appears at the strain of 0.5%~2%; strain hardening type red clay should stress and strain characteristic curve for fitting a power function model, but to strengthen the position of the inflection point is not sensitive.
2017, 25(s1): 230-234.
Guangxi is a province of aluminum production in China, in the production of aluminum will produce a red mud which would cause pollution. Because the alkaline base of red mud is difficult to remove, groundwater would be polluted. Dumping large amounts of red mud, not only take up large tracts of land, dry red mud can also cause dust pollution. Effectively recycling of red mud has become an urgent task. This study attempts to use aluminium oxide, which is as one of the main components of red mud to mixed with red clay. Researching the physical and mechanical properties of red clay which mix in alumina. This experiment adopts mixed rate respectively of 0, 1%, 2%, and 4%. Using this five mixing ratio of Al2O3. To testing its liquid-plastic limit. Analysis the liquid-plastic limit changes of red clay with different rate of the doped alumina. By compaction test, concluded that the red clay under different mixed rate of maximum dry density and the optimum moisture content. Finally, tri-axial shear test of non-consolidation and non-drainage on the reshape sample of red clay, obtained the variation of the stress-strain curves, elasticity modulus, shear strength parameter in the same moisture content, different mixing rates, under different confining pressures. The experimental results show that the modified red clay with high liquid and plastic limit features, and its status is hard. Along with the addition of aluminum oxide increases, the liquid limit, plastic limit, and plasticity index, moisture content, maximum dry density decreases; with the same alumina mixed quantity of cases, as the confining pressure increases the shear strength increased, under the same confining pressure, with the increase of alumina mixed, shear strength in the low first, then increased.
Guangxi is a province of aluminum production in China, in the production of aluminum will produce a red mud which would cause pollution. Because the alkaline base of red mud is difficult to remove, groundwater would be polluted. Dumping large amounts of red mud, not only take up large tracts of land, dry red mud can also cause dust pollution. Effectively recycling of red mud has become an urgent task. This study attempts to use aluminium oxide, which is as one of the main components of red mud to mixed with red clay. Researching the physical and mechanical properties of red clay which mix in alumina. This experiment adopts mixed rate respectively of 0, 1%, 2%, and 4%. Using this five mixing ratio of Al2O3. To testing its liquid-plastic limit. Analysis the liquid-plastic limit changes of red clay with different rate of the doped alumina. By compaction test, concluded that the red clay under different mixed rate of maximum dry density and the optimum moisture content. Finally, tri-axial shear test of non-consolidation and non-drainage on the reshape sample of red clay, obtained the variation of the stress-strain curves, elasticity modulus, shear strength parameter in the same moisture content, different mixing rates, under different confining pressures. The experimental results show that the modified red clay with high liquid and plastic limit features, and its status is hard. Along with the addition of aluminum oxide increases, the liquid limit, plastic limit, and plasticity index, moisture content, maximum dry density decreases; with the same alumina mixed quantity of cases, as the confining pressure increases the shear strength increased, under the same confining pressure, with the increase of alumina mixed, shear strength in the low first, then increased.
2017, 25(s1): 235-247.
Seepage-stress coupling in fractured rock mass is a hot and difficult issue in the field of rock mechanics and engineering research. Firstly, the research status of the experiments and mathematical models of the coupling of fractured rock mass were described systematically. Meanwhile, some common numerical analysis methods and their applications were summed up. Then the hotspots and engineering applications of coupling were summarized. According to the analysis of the research status of seepage-stress coupling, some suggestions were put forward:(1)In most of past researches, the relationship between permeability and normal stress were focused, and the effects study of shear stress or three dimensional stress on permeability were less. So the latter should be carried out. (2)In view of the difficulty of simulating the expansion of fractures by traditional numerical methods, new numerical methods that can consider the generation and expansion of fissures, such as meshless method, numerical manifold method and coupling analysis of FEM/DEM,should be developed. (3)Considering the mechanism and application study of multifield coupling of fractured rock mass in special environment, such as high or low temperature, chemical corrosion, et al. And the characteristics of rock such as heterogeneity, rheological properties should also be taken into account. (4)Although there were disparity between the existing models and the actual situations, the theories should also be fully utilized to make the design and analysis of the project more reasonable.
Seepage-stress coupling in fractured rock mass is a hot and difficult issue in the field of rock mechanics and engineering research. Firstly, the research status of the experiments and mathematical models of the coupling of fractured rock mass were described systematically. Meanwhile, some common numerical analysis methods and their applications were summed up. Then the hotspots and engineering applications of coupling were summarized. According to the analysis of the research status of seepage-stress coupling, some suggestions were put forward:(1)In most of past researches, the relationship between permeability and normal stress were focused, and the effects study of shear stress or three dimensional stress on permeability were less. So the latter should be carried out. (2)In view of the difficulty of simulating the expansion of fractures by traditional numerical methods, new numerical methods that can consider the generation and expansion of fissures, such as meshless method, numerical manifold method and coupling analysis of FEM/DEM,should be developed. (3)Considering the mechanism and application study of multifield coupling of fractured rock mass in special environment, such as high or low temperature, chemical corrosion, et al. And the characteristics of rock such as heterogeneity, rheological properties should also be taken into account. (4)Although there were disparity between the existing models and the actual situations, the theories should also be fully utilized to make the design and analysis of the project more reasonable.
2017, 25(s1): 248-252.
The toppling of the rock slope most have anti dip layered structure, the typical structural feature of the reversal incline slope is that the rock layer and the slope surface are coincident with the strike and but they have opposite dip. It's more likely to happen with different toppling failure if there are one or more sets of joints whose strike is the same as the slope cut the rock into discrete blocks. This paper combined the engineering geological condition of Longshou Mine and used the soft material small model to study the toppling caused by the open-pit mining at its body force condition of self-weight. The results show that the existence of fault destroyed the continuity of the rock mass, increased flexibility of rock mass and significantly reduces the deformation modulus of rock mass. The consequent fault located in the compression zone gets a lot of lateral force owing to the large deformation, and when the lateral force is greater than the physical component of the fault rock mass self-weight in the direction of the lateral force, it will toppling with wide-angle and reversal.
The toppling of the rock slope most have anti dip layered structure, the typical structural feature of the reversal incline slope is that the rock layer and the slope surface are coincident with the strike and but they have opposite dip. It's more likely to happen with different toppling failure if there are one or more sets of joints whose strike is the same as the slope cut the rock into discrete blocks. This paper combined the engineering geological condition of Longshou Mine and used the soft material small model to study the toppling caused by the open-pit mining at its body force condition of self-weight. The results show that the existence of fault destroyed the continuity of the rock mass, increased flexibility of rock mass and significantly reduces the deformation modulus of rock mass. The consequent fault located in the compression zone gets a lot of lateral force owing to the large deformation, and when the lateral force is greater than the physical component of the fault rock mass self-weight in the direction of the lateral force, it will toppling with wide-angle and reversal.
2017, 25(s1): 253-260.
Jinchuan nickel mine is Chinese most important nickel mineral resource base, which was characterized developed faults, structure plane and mine high grader. Longshou mine uses hexagonal approach cut and fill method. The collapse of the upper ore body and the filling body in the west mining area of Longshou Mine has a great influence on the below mining activities. This paper aims to analyze the mechanism of deformation and failure of mine body and filling. The numerical calculation model was used to analyze the changes of plastic yield zone and stress field during the process of filling and cementation. In the shallow area of mine body, the plastic yield area gradually increases with the progress of the stratified mining under the action of self-stress. Under the action of tectonic stress and self-stress, the plastic yield area of the deep mine body is larger than that of the deep ore body. With the excavation and filling, the vertical and horizontal structural stresses made the stress field redistributed, which was more favorable for the stability of rock mass. The upper plastic yield disappeared and the model entire yield area decreased. The tensile stress was mainly concentrated in the vicinity of the hexagonal section, especially the roof of rock. The horizontal and vertical tectonic stress changed the stress state of mine stope, and the tensile stress area around the hexagonal cross section decreased and the distribution was more uniform, which was favorable for the stability of the hexagonal section. But the compressive stress increased in the whole model area, and the plastic yield was easy to be far away from the hexagonal cross section. The long time cut and fill process will adversely affect the stability of the filling body and mine rock.
Jinchuan nickel mine is Chinese most important nickel mineral resource base, which was characterized developed faults, structure plane and mine high grader. Longshou mine uses hexagonal approach cut and fill method. The collapse of the upper ore body and the filling body in the west mining area of Longshou Mine has a great influence on the below mining activities. This paper aims to analyze the mechanism of deformation and failure of mine body and filling. The numerical calculation model was used to analyze the changes of plastic yield zone and stress field during the process of filling and cementation. In the shallow area of mine body, the plastic yield area gradually increases with the progress of the stratified mining under the action of self-stress. Under the action of tectonic stress and self-stress, the plastic yield area of the deep mine body is larger than that of the deep ore body. With the excavation and filling, the vertical and horizontal structural stresses made the stress field redistributed, which was more favorable for the stability of rock mass. The upper plastic yield disappeared and the model entire yield area decreased. The tensile stress was mainly concentrated in the vicinity of the hexagonal section, especially the roof of rock. The horizontal and vertical tectonic stress changed the stress state of mine stope, and the tensile stress area around the hexagonal cross section decreased and the distribution was more uniform, which was favorable for the stability of the hexagonal section. But the compressive stress increased in the whole model area, and the plastic yield was easy to be far away from the hexagonal cross section. The long time cut and fill process will adversely affect the stability of the filling body and mine rock.
2017, 25(s1): 261-265.
Anchor cable failure is mainly caused by pre-stressed anchor cable's pre-stressing loss. Prestress loss is ineluctability, but it could be taken measures to ensure the effect of the anchor cable prestress. This paper analyzed the rule of pre-stress changing, the factors that make the anchor cable's pre-stress changing and also the impact on the pre-stress changing by means of anchor cable's monitoring data and slope deformation monitoring data. The results show that the fastest stage of pre-stress loss occurred in a period of time after anchor cable tension; optimization measures can be used to ensure the initial effective pre-stress; the period of pre-stress quickly reduce continuous long time in slope reinforcement with anchor acble.
Anchor cable failure is mainly caused by pre-stressed anchor cable's pre-stressing loss. Prestress loss is ineluctability, but it could be taken measures to ensure the effect of the anchor cable prestress. This paper analyzed the rule of pre-stress changing, the factors that make the anchor cable's pre-stress changing and also the impact on the pre-stress changing by means of anchor cable's monitoring data and slope deformation monitoring data. The results show that the fastest stage of pre-stress loss occurred in a period of time after anchor cable tension; optimization measures can be used to ensure the initial effective pre-stress; the period of pre-stress quickly reduce continuous long time in slope reinforcement with anchor acble.
2017, 25(s1): 266-273.
The geological conditions in the Three Gorges Reservoir area of the Yangtze River are complicated. The main distribution strata of the Wuxia Gorge narrows in Wushan County are the Triassic Daye Formation and the Jialingjiang Formation limestone, in which the north bank of the Yangtze River is dominated by the anti-dip rocky reservoir bank. In the long geological history of the evolutionary process, a number of bank slopes and dangerous rocks of poor stability have been formed, resulting in further deterioration of the stability of the Three Gorges reservoir after impoundment. On November 23, 2008(two months after the 175m experimental impoundment of the Three Gorges Reservoir), 380000m3 dangerous rock at Gongjiafang collapsed, generating a surge with a height of 13m, which was a serious threat to the safety of the Yangtze River channel. Wuxia Gorge is characterized by large terrain height difference, steep slope, large scale of the potential landslide body and difficult to control. Based on the study of the deformation and instability characteristics of a section of the dangerous rock mass between Gongjiafang and Dulong on the north bank of the Wuxia River, the prevention and control measures of the reservoir bank of poor stability were researched and discussed, providing a certain reference value for the comprehensive improvement of the dangerous rock slope.
The geological conditions in the Three Gorges Reservoir area of the Yangtze River are complicated. The main distribution strata of the Wuxia Gorge narrows in Wushan County are the Triassic Daye Formation and the Jialingjiang Formation limestone, in which the north bank of the Yangtze River is dominated by the anti-dip rocky reservoir bank. In the long geological history of the evolutionary process, a number of bank slopes and dangerous rocks of poor stability have been formed, resulting in further deterioration of the stability of the Three Gorges reservoir after impoundment. On November 23, 2008(two months after the 175m experimental impoundment of the Three Gorges Reservoir), 380000m3 dangerous rock at Gongjiafang collapsed, generating a surge with a height of 13m, which was a serious threat to the safety of the Yangtze River channel. Wuxia Gorge is characterized by large terrain height difference, steep slope, large scale of the potential landslide body and difficult to control. Based on the study of the deformation and instability characteristics of a section of the dangerous rock mass between Gongjiafang and Dulong on the north bank of the Wuxia River, the prevention and control measures of the reservoir bank of poor stability were researched and discussed, providing a certain reference value for the comprehensive improvement of the dangerous rock slope.
2017, 25(s1): 274-278.
The Tangyang landslide section close to the dam located in Kajiwa reservoir. Its huge scale, has a certain effect on power plant engineering. According to the research on the geological conditions, deformation characteristics and the formation mechanism of the slope, according to the data, earthquake, rainstorm, leading edge, landslide, the status of the landslide is evaluated by 5 factors. The rigid body limit equilibrium method and the FLAC3D quantitative calculation are carried out. The qualitative and quantitative evaluation are basically the same.
The Tangyang landslide section close to the dam located in Kajiwa reservoir. Its huge scale, has a certain effect on power plant engineering. According to the research on the geological conditions, deformation characteristics and the formation mechanism of the slope, according to the data, earthquake, rainstorm, leading edge, landslide, the status of the landslide is evaluated by 5 factors. The rigid body limit equilibrium method and the FLAC3D quantitative calculation are carried out. The qualitative and quantitative evaluation are basically the same.
2017, 25(s1): 279-283.
In Zambia, the activities of ants are intense. The ant caves are everywhere, with different sizes and heights. Cavities exist in the ant mounds above the surface and in the ant caves underground. The cavities underground have great effects on the foundations and the basis of the construction. As only a few large-scaled programs such as the runways of the airport are in Zambia, few researches on the influences and the treatments of the ant caves on the constructions had been done. Therefore, it is rather important to study the impacts of the ant caves on the constructions of the International Airport in Zambia. This essay is based on the materials of investigation and the monographic study on the International Airport in Zambia. Through the field investigation, excavation of the ant caves, field load tests, infiltration tests and the soil tests, we get to find out the categories, the scope of influence and the physical and mechanical properties of the ant caves. As the ant caves have the harmful uneven settlements impact on the construction of the Airport, it is suggested that the comprehensive treatment measures should be taken such as clearing, dynamic compactions, grouting and ant-killed medicines and so on.
In Zambia, the activities of ants are intense. The ant caves are everywhere, with different sizes and heights. Cavities exist in the ant mounds above the surface and in the ant caves underground. The cavities underground have great effects on the foundations and the basis of the construction. As only a few large-scaled programs such as the runways of the airport are in Zambia, few researches on the influences and the treatments of the ant caves on the constructions had been done. Therefore, it is rather important to study the impacts of the ant caves on the constructions of the International Airport in Zambia. This essay is based on the materials of investigation and the monographic study on the International Airport in Zambia. Through the field investigation, excavation of the ant caves, field load tests, infiltration tests and the soil tests, we get to find out the categories, the scope of influence and the physical and mechanical properties of the ant caves. As the ant caves have the harmful uneven settlements impact on the construction of the Airport, it is suggested that the comprehensive treatment measures should be taken such as clearing, dynamic compactions, grouting and ant-killed medicines and so on.
2017, 25(s1): 284-288.
At present, the widely used method of regional debris flow hazard assessment was proposed by Liu Xi-lin. Because the method is based on administrative region as assessment unit, it does not reflect the geomorphic conditions of debris flow, and it is difficult to get some assessment indexes. Based on watershed unit, the article establishes the assessment system of debris flow. According to the topographic conditions, source conditions and hydrodynamic conditions required for the formation of debris flow, the factors related to debris flow source, channel and rainfall are selected and assigned as the assessment index, which are analyzed and evaluated using GIS technique. Taking the Dadu river basin as an example, according to the development characteristics of debris flow, relevant factors and indexes are selected to evaluate debris flow hazard; the evaluation results are in accordance with the actual situation, which is helpful for planning to reduce the damage by government.
At present, the widely used method of regional debris flow hazard assessment was proposed by Liu Xi-lin. Because the method is based on administrative region as assessment unit, it does not reflect the geomorphic conditions of debris flow, and it is difficult to get some assessment indexes. Based on watershed unit, the article establishes the assessment system of debris flow. According to the topographic conditions, source conditions and hydrodynamic conditions required for the formation of debris flow, the factors related to debris flow source, channel and rainfall are selected and assigned as the assessment index, which are analyzed and evaluated using GIS technique. Taking the Dadu river basin as an example, according to the development characteristics of debris flow, relevant factors and indexes are selected to evaluate debris flow hazard; the evaluation results are in accordance with the actual situation, which is helpful for planning to reduce the damage by government.
2017, 25(s1): 289-294.
The top of the high-steep slope are usually arduous and unreachable, the identification and evaluation of high position geological disaster are the difficult problem in the disaster prevention. Based on a typical high and steep slope and aided by the unmanned aerial vehicle photograph, to identify the geological characteristics of potential unstable rock mass and deformation rock mass on the top part of the steep-slope. Digital photogrammetry technology were used to obtain the information of the rock mass structure and the geometric characteristics. Studied the stability of the potential unstable rock mass, trajectory of the falling rock mass and the impact energy, then the slope geological hazard were evaluated. Vulnerability analysis and economic loss calculation after disaster of the three types of structures, such as bridge, subgrade, shed tunnel, showed that the shed tunnel is the best, and if the other structures are used, it is necessary to reinforce the slope.
The top of the high-steep slope are usually arduous and unreachable, the identification and evaluation of high position geological disaster are the difficult problem in the disaster prevention. Based on a typical high and steep slope and aided by the unmanned aerial vehicle photograph, to identify the geological characteristics of potential unstable rock mass and deformation rock mass on the top part of the steep-slope. Digital photogrammetry technology were used to obtain the information of the rock mass structure and the geometric characteristics. Studied the stability of the potential unstable rock mass, trajectory of the falling rock mass and the impact energy, then the slope geological hazard were evaluated. Vulnerability analysis and economic loss calculation after disaster of the three types of structures, such as bridge, subgrade, shed tunnel, showed that the shed tunnel is the best, and if the other structures are used, it is necessary to reinforce the slope.
2017, 25(s1): 295-300.
The Beijing Capital International Airport Terminal 2 has been built using more than ten years. In recent years, the ground fissures have been found in the Z2-Z3-F region. The ground fissures made the road surface uneven, have affected the normal use of the Terminal 2. In order to find out the characteristics and causes of the ground fissures, and provide basis for the prevention and control of the ground fissures, by collecting and summarizing related literature and survey data, comprehensive geophysical prospecting method, road surface displacement monitoring results. Briefly introduces regional geological environment background of the ground fissures, and preliminarily studies the main features of ground fissures and systematically analyzes the factors and mechanism of ground fissure disaster at last. Tectonic activity is the intrinsic factors that give rise to the ground fissures disaster, is the main cause of the formation and development of the ground fissures, the ground uneven settlement caused by the underground water level changing, is the extrinsic factor, it is also an cause of the development of ground fissures. Pointed out that it is not feasible and economical to use the engineering measures to cure the ground fissures radically. Thus, a few pieces of preventive advice and measures are proposed, such as the internet of things technology, it provides a useful reference for the treatment of the ground fissures in the future.
The Beijing Capital International Airport Terminal 2 has been built using more than ten years. In recent years, the ground fissures have been found in the Z2-Z3-F region. The ground fissures made the road surface uneven, have affected the normal use of the Terminal 2. In order to find out the characteristics and causes of the ground fissures, and provide basis for the prevention and control of the ground fissures, by collecting and summarizing related literature and survey data, comprehensive geophysical prospecting method, road surface displacement monitoring results. Briefly introduces regional geological environment background of the ground fissures, and preliminarily studies the main features of ground fissures and systematically analyzes the factors and mechanism of ground fissure disaster at last. Tectonic activity is the intrinsic factors that give rise to the ground fissures disaster, is the main cause of the formation and development of the ground fissures, the ground uneven settlement caused by the underground water level changing, is the extrinsic factor, it is also an cause of the development of ground fissures. Pointed out that it is not feasible and economical to use the engineering measures to cure the ground fissures radically. Thus, a few pieces of preventive advice and measures are proposed, such as the internet of things technology, it provides a useful reference for the treatment of the ground fissures in the future.
2017, 25(s1): 301-308.
By simulating the complex mountain building slope in natural, storm and earthquake conditions, the research targeted how the properties of soft interlayer or anti-slide pile diameters affect the stability, and also investigated the plastic failure area distribution. The results show:(1)The stability has obviously promoted after the pit is backfilled, especially in the storm condition. (2)After the anti-slide pile reinforced the slope, the damage caused by earthquake is faintly. But the pile diameter is critical in the storm condition. (3)When the pile diameter is small, the anti-slide piles and anchor cable have reinforce the slope together. As the pile diameter increase, the anchor cable becomes ineffective. (4)Under a smaller angle, the plastic failure area is located in the soft interlayer by shear failure. When the angle takes the maximum, the failure area transfers to the shallow soil by tensile failure.
By simulating the complex mountain building slope in natural, storm and earthquake conditions, the research targeted how the properties of soft interlayer or anti-slide pile diameters affect the stability, and also investigated the plastic failure area distribution. The results show:(1)The stability has obviously promoted after the pit is backfilled, especially in the storm condition. (2)After the anti-slide pile reinforced the slope, the damage caused by earthquake is faintly. But the pile diameter is critical in the storm condition. (3)When the pile diameter is small, the anti-slide piles and anchor cable have reinforce the slope together. As the pile diameter increase, the anchor cable becomes ineffective. (4)Under a smaller angle, the plastic failure area is located in the soft interlayer by shear failure. When the angle takes the maximum, the failure area transfers to the shallow soil by tensile failure.
2017, 25(s1): 309-315.
Quantitative assessment of regional hazard is an important item of risk analysis. In this paper, it aims to realize the spatial-temporal probability when induced factors are unavailable. For the Yuyangguan county, in the southwest Hubei province, China, we achieved landslide hazard probability at large scale combining the spatial probability, temporal and exceedance probability. We obtained the spatial probability of landslide-occurrence by Weights of Evidence model based on 9 indicators, including slope, elevation, aspect, plan curvature, lithology, et al.,with success rate 0.84 and prediction rate 0.74. Based on the assumption of a Poisson distribution, we obtained temporal probability for four return periods(5, 10, 20 and 50 years).Using the statistics of landslide magnitude and frequency, the exceedance probability was achieved for two volume scenarios(50000 cubic meters, 100, 000 cubic meters).Lastly, we obtained landslide hazard maps for four periods, from 5 to 50 years, and for landslide two volume scenarios(AL 50000m3, and AL 100000m3). The results showed that in ten years return period, landslide probability would be 0.2-0.3 and 0.1-0.2 respectively at two volume scenarios, mainly concentrate at the urban construction areas along both sides of Yuyangguan river. With the increase of recurrence period, the probability of landslide hazard would increase to 0.5-0.6, 0.3-0.4,with the affected area extended to Dongwan, Hutounao and Sanfangping. The conclusion can provide scientific support for urban construction in mountainous towns.
Quantitative assessment of regional hazard is an important item of risk analysis. In this paper, it aims to realize the spatial-temporal probability when induced factors are unavailable. For the Yuyangguan county, in the southwest Hubei province, China, we achieved landslide hazard probability at large scale combining the spatial probability, temporal and exceedance probability. We obtained the spatial probability of landslide-occurrence by Weights of Evidence model based on 9 indicators, including slope, elevation, aspect, plan curvature, lithology, et al.,with success rate 0.84 and prediction rate 0.74. Based on the assumption of a Poisson distribution, we obtained temporal probability for four return periods(5, 10, 20 and 50 years).Using the statistics of landslide magnitude and frequency, the exceedance probability was achieved for two volume scenarios(50000 cubic meters, 100, 000 cubic meters).Lastly, we obtained landslide hazard maps for four periods, from 5 to 50 years, and for landslide two volume scenarios(AL 50000m3, and AL 100000m3). The results showed that in ten years return period, landslide probability would be 0.2-0.3 and 0.1-0.2 respectively at two volume scenarios, mainly concentrate at the urban construction areas along both sides of Yuyangguan river. With the increase of recurrence period, the probability of landslide hazard would increase to 0.5-0.6, 0.3-0.4,with the affected area extended to Dongwan, Hutounao and Sanfangping. The conclusion can provide scientific support for urban construction in mountainous towns.
2017, 25(s1): 316-324.
This article collects the deformation characteristics of tunnel inside structures and outside slopes for right side tunnel of Tianhe Tunnel of Ya'an-Kangding Expressway. With assistance of supplementary investigation of geological data which including engineering geological mapping, engineering geological drilling, monitoring and measurement in tunnel, displacement monitoring of slope surface and deep displacement monitoring in drilling hole, the cause of deformation of the above tunnel section is thus discussed and analyzed. It reveals that such non-layered rock structure is influenced by vicinity tectonics and unfavorable structural plane of extroversion is developed. Especially, multi-stage eruptions and sedimentary cycle ever appeared in the local basalt tectonics and the eruption interval is long which leads to complex lithology, and in addition, pelitic siltstone or silty tuff with 4m thickness the most is found in the investigated area. Under the impact of adverse working conditions such as shallow cover, artificial excavation disturbance and precipitation, tectonic bias or bedding-like slippage is probably generated along the structural plane of extroversion and lithologic boundary. In the following treatment design and construction, according to the pre-survey for the characteristics and genetic analysis of the deformation, we designed the targeted deformation treatments for different sub-section, and continued to strengthen the construction monitoring and measurement. At the time of the announcement, the deformation section of the tunnel has been completed and the tunnel has been broken through. The monitoring inside and outside the cave revealed the overall stability of the slope. The tunnel structure was in a convergent state of deformation. So, it is necessary to reacquaint the structural characteristics and physical-mechanical properties of such massive rock which evidently has theoretical research value and practical guidance significance for similar engineering project.
This article collects the deformation characteristics of tunnel inside structures and outside slopes for right side tunnel of Tianhe Tunnel of Ya'an-Kangding Expressway. With assistance of supplementary investigation of geological data which including engineering geological mapping, engineering geological drilling, monitoring and measurement in tunnel, displacement monitoring of slope surface and deep displacement monitoring in drilling hole, the cause of deformation of the above tunnel section is thus discussed and analyzed. It reveals that such non-layered rock structure is influenced by vicinity tectonics and unfavorable structural plane of extroversion is developed. Especially, multi-stage eruptions and sedimentary cycle ever appeared in the local basalt tectonics and the eruption interval is long which leads to complex lithology, and in addition, pelitic siltstone or silty tuff with 4m thickness the most is found in the investigated area. Under the impact of adverse working conditions such as shallow cover, artificial excavation disturbance and precipitation, tectonic bias or bedding-like slippage is probably generated along the structural plane of extroversion and lithologic boundary. In the following treatment design and construction, according to the pre-survey for the characteristics and genetic analysis of the deformation, we designed the targeted deformation treatments for different sub-section, and continued to strengthen the construction monitoring and measurement. At the time of the announcement, the deformation section of the tunnel has been completed and the tunnel has been broken through. The monitoring inside and outside the cave revealed the overall stability of the slope. The tunnel structure was in a convergent state of deformation. So, it is necessary to reacquaint the structural characteristics and physical-mechanical properties of such massive rock which evidently has theoretical research value and practical guidance significance for similar engineering project.
2017, 25(s1): 325-331.
The excavated in the mountain for a mining tunnel will have both advantages and disadvantages on the stability of the slope, and the adverse effects may lead to serious consequences such as failure of slope. In this paper, a series of generalized slope model is established. Based on the three dimensional fast Lagrangian analysis of continua, the numerical simulation software FLAC3D is used to simulate the excavation at different locations of the generalized model. The stability of the slope after excavation is analyzed, and the influence of mine location on slope stability is summarized. In order to verify the rule from the generalized model, the physical model is established and the numerical simulation is carried out with the background of the geological landslides disaster of Shanyang in Shaanxi Province. The results show that when the excavation is in the shoulder position, the slope is more stable than that without excavation. When the excavation position near the slope, the stability of the slope is reduced. When the excavation is gradually moved from the surface to the inside of the slope, the stability of the slope decreases first and then increases, especially when the excavation is near the most dangerous sliding surface, the slope has its lowest stability. This paper can be used as the theoretical guidance for the activity of mine slope safety.
The excavated in the mountain for a mining tunnel will have both advantages and disadvantages on the stability of the slope, and the adverse effects may lead to serious consequences such as failure of slope. In this paper, a series of generalized slope model is established. Based on the three dimensional fast Lagrangian analysis of continua, the numerical simulation software FLAC3D is used to simulate the excavation at different locations of the generalized model. The stability of the slope after excavation is analyzed, and the influence of mine location on slope stability is summarized. In order to verify the rule from the generalized model, the physical model is established and the numerical simulation is carried out with the background of the geological landslides disaster of Shanyang in Shaanxi Province. The results show that when the excavation is in the shoulder position, the slope is more stable than that without excavation. When the excavation position near the slope, the stability of the slope is reduced. When the excavation is gradually moved from the surface to the inside of the slope, the stability of the slope decreases first and then increases, especially when the excavation is near the most dangerous sliding surface, the slope has its lowest stability. This paper can be used as the theoretical guidance for the activity of mine slope safety.
2017, 25(s1): 332-336.
Study the correlation analysis of land subsidence, groundwater level and formation lithology based on the land subsidence monitoring data in recent fifty years, put forward that land subsidence in Xi'an is mainly controlled by the properties of rock and soil and water exploitation, and consider that sand and clay interbed structure is the internal reasons of ground subsidence, groundwater over exploitation is inducing factors of land subsidence, the two and the ground settlement are the specific high correlation. The susceptibility, distribution range and amount of land subsidence are jointly determined by thickness ratio of cohesive soil and underground water level dynamic. In this paper, a new method to study the mechanism of land subsidence is explored, which has a positive significance to master the law of ground subsidence development, predicting the development of land subsidence and effectively preventing and controlling land subsidence.
Study the correlation analysis of land subsidence, groundwater level and formation lithology based on the land subsidence monitoring data in recent fifty years, put forward that land subsidence in Xi'an is mainly controlled by the properties of rock and soil and water exploitation, and consider that sand and clay interbed structure is the internal reasons of ground subsidence, groundwater over exploitation is inducing factors of land subsidence, the two and the ground settlement are the specific high correlation. The susceptibility, distribution range and amount of land subsidence are jointly determined by thickness ratio of cohesive soil and underground water level dynamic. In this paper, a new method to study the mechanism of land subsidence is explored, which has a positive significance to master the law of ground subsidence development, predicting the development of land subsidence and effectively preventing and controlling land subsidence.
2017, 25(s1): 337-348.
Recent years, with the development of national economy, specially on hydropower project construction which brings many problems such as high slope, and disasters like debris flows. Therefore, people pay more attention to the investigation of potential risks on geological hazards. This article combines the typical engineering cases, classifies the engineering bank slopes and their mainly damage types, explains how to carry out disaster potential risks identification, the main measures of disaster reduction and disaster prevention are expounded. And discusses the key points of potential risks identification of the construction of hydropower project. It is a good reference and guidance for people to recognize and pay attention to the potential risks of slope.
Recent years, with the development of national economy, specially on hydropower project construction which brings many problems such as high slope, and disasters like debris flows. Therefore, people pay more attention to the investigation of potential risks on geological hazards. This article combines the typical engineering cases, classifies the engineering bank slopes and their mainly damage types, explains how to carry out disaster potential risks identification, the main measures of disaster reduction and disaster prevention are expounded. And discusses the key points of potential risks identification of the construction of hydropower project. It is a good reference and guidance for people to recognize and pay attention to the potential risks of slope.
2017, 25(s1): 349-356.
Yindongzi gully is a typical small watershed debris flow in earthquake stricken area where 14 debris flow events happened from 2009 rainy season beginning to the end of rainy season in 2013,which is the result of Wenchuan earthquake and subsequent heavy rainfall for several years. Therefore, it is very significantly to study the mechanism and procession of debris flow for understanding its long-term activities and riskness in earthquake disturbed area. The characteristics of material supplies and rainfall condition have been analyzed by filed investigation, experiment and collecting antecedent rainfall events reference, and calculating some parameters of debris flow, such as density, velocity, etc. Finally, the riskness of Yindongzi gully is analyzed according to the volume of material supplies presently and,providing some advices for debris flow prevention. The conclusion are that(1):After Wenchuan earthquake, Yindongzi debris flow is a frequently and diluted debris flow, and frequency is 3.5 times a year while density is 1.5~1.6tm-3.(2)During 7 years of water erosion the total volume of material supplies decreased from 35.93104m3 to 23.02104m3, and the percentage of fine particles that smaller than 10mm reduced from 27.04%to 18.22%,which indicate that Yindongzi debris flow events will be diluted debris flow type.(3)When rainfall duration more than 8 hours, the mean rainfall intensity will be 11.53mmh-1 that less than the average value of the whole Wenchuan earthquake striken area. Therefore, Yindongzi gully in high dangerous condition presently.
Yindongzi gully is a typical small watershed debris flow in earthquake stricken area where 14 debris flow events happened from 2009 rainy season beginning to the end of rainy season in 2013,which is the result of Wenchuan earthquake and subsequent heavy rainfall for several years. Therefore, it is very significantly to study the mechanism and procession of debris flow for understanding its long-term activities and riskness in earthquake disturbed area. The characteristics of material supplies and rainfall condition have been analyzed by filed investigation, experiment and collecting antecedent rainfall events reference, and calculating some parameters of debris flow, such as density, velocity, etc. Finally, the riskness of Yindongzi gully is analyzed according to the volume of material supplies presently and,providing some advices for debris flow prevention. The conclusion are that(1):After Wenchuan earthquake, Yindongzi debris flow is a frequently and diluted debris flow, and frequency is 3.5 times a year while density is 1.5~1.6tm-3.(2)During 7 years of water erosion the total volume of material supplies decreased from 35.93104m3 to 23.02104m3, and the percentage of fine particles that smaller than 10mm reduced from 27.04%to 18.22%,which indicate that Yindongzi debris flow events will be diluted debris flow type.(3)When rainfall duration more than 8 hours, the mean rainfall intensity will be 11.53mmh-1 that less than the average value of the whole Wenchuan earthquake striken area. Therefore, Yindongzi gully in high dangerous condition presently.
2017, 25(s1): 357-364.
Soil of debris flow has a broadly graded weight distribution, a great disparity in size, a high dispersion in fine components, which caused the effects of Particles Transport on Soil Pores Clogging(PTSPC)in the process of rainfall and seepage. Due to the interaction between soil and rainwater, small particles can be detached and transported, some of them may clog at pores, PTSPC decreased the permeability of soils in debris flow sources, PTSPC played an important role in the process of debris flow preparation and initiation. This research article summarized extensive literature of debris flow, and reviews relevant fine particles transport at home and abroad. Finally, several research directions were proposed based on the effects of PTSPC.The study provided new ideas for the mechanism of rainfall-induced debris flow, and a theoretical basis for disaster prevention and mitigation.
Soil of debris flow has a broadly graded weight distribution, a great disparity in size, a high dispersion in fine components, which caused the effects of Particles Transport on Soil Pores Clogging(PTSPC)in the process of rainfall and seepage. Due to the interaction between soil and rainwater, small particles can be detached and transported, some of them may clog at pores, PTSPC decreased the permeability of soils in debris flow sources, PTSPC played an important role in the process of debris flow preparation and initiation. This research article summarized extensive literature of debris flow, and reviews relevant fine particles transport at home and abroad. Finally, several research directions were proposed based on the effects of PTSPC.The study provided new ideas for the mechanism of rainfall-induced debris flow, and a theoretical basis for disaster prevention and mitigation.
2017, 25(s1): 365-373.
The Jiaobangou Basin in Dechang county have some features such as large watershed area, complex and diverse topography, rich rainfall and abundant sources which provide the potential conditions for causing debris flow. This paper analyzes the pregnant environment characteristics and the formation conditions of debris flow, and divides the multi-scale assessment units of debris flow watershed based on topography and geological conditions. On the basis of analysis, the debris flow hazards are quantitative assessed by the multi-factor coupling method of topography, geology and hydrology. Using the method of hydrological analysis, Jiaobangou watershed, the watershed area of 45.71km2,which divided into 28 assessment units(8 units in the early mature stage, 13 units in the full mature stage, 5 units in the late mature stage and 2 units in the old stage), is accurately calculated 8 high hazard areas, 6 medium hazard areas, 10 low hazard areas and 4 safe areas. The hazard assessment is close to actual experiences in Jiaobangou watershed, which can provide great significance to the disaster prevention and mitigation in the area.
The Jiaobangou Basin in Dechang county have some features such as large watershed area, complex and diverse topography, rich rainfall and abundant sources which provide the potential conditions for causing debris flow. This paper analyzes the pregnant environment characteristics and the formation conditions of debris flow, and divides the multi-scale assessment units of debris flow watershed based on topography and geological conditions. On the basis of analysis, the debris flow hazards are quantitative assessed by the multi-factor coupling method of topography, geology and hydrology. Using the method of hydrological analysis, Jiaobangou watershed, the watershed area of 45.71km2,which divided into 28 assessment units(8 units in the early mature stage, 13 units in the full mature stage, 5 units in the late mature stage and 2 units in the old stage), is accurately calculated 8 high hazard areas, 6 medium hazard areas, 10 low hazard areas and 4 safe areas. The hazard assessment is close to actual experiences in Jiaobangou watershed, which can provide great significance to the disaster prevention and mitigation in the area.
2017, 25(s1): 374-376.
By 2013,there are a total of 5001 types of Mines in Shanxi Province, and the mining area of 13233.74km2. The amount of 5 types of geological disasterslandslides, landslides, debris flows, ground fissures, ground collapse-aggregate 3828,the impact of about 326.50km2 and direct economic loss of 891.4157million yuan; among them, the ground collapse and ground fissures accounted for 78.37% of the total geological disasters, as the main types of disaster, and caused economic loss and potential threat to the maximum. During nine years, 2004~2013,the total number of geological disasters in the province increased by 80%,the overall growth trend in the main, especially in the collapse of the largest increase from 21 to 404; the overall scale of the disaster is main small, but large scale increased significantly, from 78 to 764 increase. Under current conditions, capacity building ahead of production in severe overcapacity, weak demand and mineral resources, resulting in mining margins, mining intensity, and the elimination of backward production capacity, improve the implementation of ecological compensation mechanism of the policy, so the expected number of geological disaster in the future growth will slow down.
By 2013,there are a total of 5001 types of Mines in Shanxi Province, and the mining area of 13233.74km2. The amount of 5 types of geological disasterslandslides, landslides, debris flows, ground fissures, ground collapse-aggregate 3828,the impact of about 326.50km2 and direct economic loss of 891.4157million yuan; among them, the ground collapse and ground fissures accounted for 78.37% of the total geological disasters, as the main types of disaster, and caused economic loss and potential threat to the maximum. During nine years, 2004~2013,the total number of geological disasters in the province increased by 80%,the overall growth trend in the main, especially in the collapse of the largest increase from 21 to 404; the overall scale of the disaster is main small, but large scale increased significantly, from 78 to 764 increase. Under current conditions, capacity building ahead of production in severe overcapacity, weak demand and mineral resources, resulting in mining margins, mining intensity, and the elimination of backward production capacity, improve the implementation of ecological compensation mechanism of the policy, so the expected number of geological disaster in the future growth will slow down.
2017, 25(s1): 377-383.
Many scholars at home and abroad field tests considering regional special soil slope effect of atmospheric environment, especially to the expansion of field tests on soil slope more deeply, and the study on the red clay slope is relatively small. In China, the red clay is widely distributed and its engineering properties are complex. The engineering problems related to the red clay slope are often encountered on the project. If the red clay slope is neglected, it is easy to cause the engineering disaster. Therefore, the establishment of the in situ monitoring system of red clay slope in Guilin city of Guangxi Yanshan area, set up a small weather station, the measurement system of soil moisture and buried TDR thermistor temperature sensor, tracking test the evolution of red clay slope soil water content and soil temperature with climate change, to provide a reference for the follow-up related to the verification model scholars. The monitoring results show that the net radiation and atmospheric temperature are the main factors affecting the slope soil temperature change of red clay, soil temperature change may indirectly reflect the changes of soil moisture content; temperature range of slope of red clay, toe temperature minimum; change slope soil water content are the main factors influencing the red clay slope the stability of the temperature changes play a role in promoting, the coupling effect of temperature and humidity of the two eventually lead to the instability of slope.
Many scholars at home and abroad field tests considering regional special soil slope effect of atmospheric environment, especially to the expansion of field tests on soil slope more deeply, and the study on the red clay slope is relatively small. In China, the red clay is widely distributed and its engineering properties are complex. The engineering problems related to the red clay slope are often encountered on the project. If the red clay slope is neglected, it is easy to cause the engineering disaster. Therefore, the establishment of the in situ monitoring system of red clay slope in Guilin city of Guangxi Yanshan area, set up a small weather station, the measurement system of soil moisture and buried TDR thermistor temperature sensor, tracking test the evolution of red clay slope soil water content and soil temperature with climate change, to provide a reference for the follow-up related to the verification model scholars. The monitoring results show that the net radiation and atmospheric temperature are the main factors affecting the slope soil temperature change of red clay, soil temperature change may indirectly reflect the changes of soil moisture content; temperature range of slope of red clay, toe temperature minimum; change slope soil water content are the main factors influencing the red clay slope the stability of the temperature changes play a role in promoting, the coupling effect of temperature and humidity of the two eventually lead to the instability of slope.
2017, 25(s1): 384-389.
On July 26, 2016, a heavy rainfall suddenly happened in Wolong County, Sichuan Province, which caused mountain torrents across the Wolong territory of Pitiao River tributary, inducing debris flow disaster. Based on environmental geologic conditions, especially characteristics of the source conditions under heavy rainfall condition, the authors discussed the starting and accumulating process and disaster characteristics of Xiongmaogou debris flow. The results showed that heavy rainfall was the dynamic factor for debris flow to occur; the disaster scale was large, which poured about 50million cubic meters earthwork; since no debris flow protection engineering was built in the channel, and the flood control facilities construction standards was low, the flood control dam was filled with mud and the fluid overflowed the river and rushed to the downstream houses, resulting in serious disasters. The typical example of Xiongmaogou debris flow indicated that debris flow in Wenchuan earthquake area has become active. Therefore, it's necessary to carry out debris flow risk assessment and monitoring and disaster early warning in Wenchuan earthquake area, and to take effective engineering measures to control the occurrence of debris flow to reduce the damage.
On July 26, 2016, a heavy rainfall suddenly happened in Wolong County, Sichuan Province, which caused mountain torrents across the Wolong territory of Pitiao River tributary, inducing debris flow disaster. Based on environmental geologic conditions, especially characteristics of the source conditions under heavy rainfall condition, the authors discussed the starting and accumulating process and disaster characteristics of Xiongmaogou debris flow. The results showed that heavy rainfall was the dynamic factor for debris flow to occur; the disaster scale was large, which poured about 50million cubic meters earthwork; since no debris flow protection engineering was built in the channel, and the flood control facilities construction standards was low, the flood control dam was filled with mud and the fluid overflowed the river and rushed to the downstream houses, resulting in serious disasters. The typical example of Xiongmaogou debris flow indicated that debris flow in Wenchuan earthquake area has become active. Therefore, it's necessary to carry out debris flow risk assessment and monitoring and disaster early warning in Wenchuan earthquake area, and to take effective engineering measures to control the occurrence of debris flow to reduce the damage.
2017, 25(s1): 390-399.
In recent years, the control of dangerous rockmass in Chongqing region showed that current classification scheme of dangerous rockmass lacked unified definition and connotation, thus easily leading to confusion and controversy, and meanwhile, difficult classification of some dangerous rockmass. Directing at the deficiencies of current classification scheme of dangerous rockmass, this thesis, based on the analysis and summary of domestic chief classification scheme of dangerous rockmass, studied the problem of classification scheme of dangerous rockmass combining with the investigation results of typical accidents of dangerous rockmass slumping happening in recent years. Firstly, according to the initial movement mode of dangerous rockmass failure, it divided dangerous rockmass into such six modes as toppling, sliding, shearing, overhanging, subsiding and falling with 11 subclasses based on differences of combination characteristics of fissure and influencing factors; Secondly, it conducted a detailed definition, location and characteristics of controlling fissure, formation conditions and influencing factors, deformation mechanism, and finally, it analyzed and explained them integrating with typical cases of dangerous rockmass slumping. As the new classification of dangerous rockmass was inclusive, clearly defined and specified as well as highly practical, it could effectively guide the exploration and evaluation, monitoring and forecasting, control of dangerous rockmass.
In recent years, the control of dangerous rockmass in Chongqing region showed that current classification scheme of dangerous rockmass lacked unified definition and connotation, thus easily leading to confusion and controversy, and meanwhile, difficult classification of some dangerous rockmass. Directing at the deficiencies of current classification scheme of dangerous rockmass, this thesis, based on the analysis and summary of domestic chief classification scheme of dangerous rockmass, studied the problem of classification scheme of dangerous rockmass combining with the investigation results of typical accidents of dangerous rockmass slumping happening in recent years. Firstly, according to the initial movement mode of dangerous rockmass failure, it divided dangerous rockmass into such six modes as toppling, sliding, shearing, overhanging, subsiding and falling with 11 subclasses based on differences of combination characteristics of fissure and influencing factors; Secondly, it conducted a detailed definition, location and characteristics of controlling fissure, formation conditions and influencing factors, deformation mechanism, and finally, it analyzed and explained them integrating with typical cases of dangerous rockmass slumping. As the new classification of dangerous rockmass was inclusive, clearly defined and specified as well as highly practical, it could effectively guide the exploration and evaluation, monitoring and forecasting, control of dangerous rockmass.
2017, 25(s1): 400-406.
Landslide-debris flow usually triggered by heavy rainfall is a kind of great hazard chain. This paper takes the landslide-debris flow which is located at the southern Dagou Village of Mapaoquan Town, Tianshui City, Gansu Province as an example. In order to get the physical parameters needed in the simulation, 4 groups of mudstone samples were taken from the lateral sliding surface of landslide area to conduct consolidated undrained(CU)triaxial tests and some conventional laboratory tests. The above experiments show that the friction angle of saturated mudstone is 11nd is smaller than that of channel slope. Based on the experimental results, we utilized LS-RAPID which is a simulation software system to simulate the movement process of the landslide-debris flow. The simulation results show that the landslide sliding average speed is 5.2ms-1 when it moved to toe of slope. The landslide was converted into debris flow under the powerful impact in the sliding process of landslide, then caused larger disaster area. Accumulation range and shape of simulation and actual measurement are the similar.
Landslide-debris flow usually triggered by heavy rainfall is a kind of great hazard chain. This paper takes the landslide-debris flow which is located at the southern Dagou Village of Mapaoquan Town, Tianshui City, Gansu Province as an example. In order to get the physical parameters needed in the simulation, 4 groups of mudstone samples were taken from the lateral sliding surface of landslide area to conduct consolidated undrained(CU)triaxial tests and some conventional laboratory tests. The above experiments show that the friction angle of saturated mudstone is 11nd is smaller than that of channel slope. Based on the experimental results, we utilized LS-RAPID which is a simulation software system to simulate the movement process of the landslide-debris flow. The simulation results show that the landslide sliding average speed is 5.2ms-1 when it moved to toe of slope. The landslide was converted into debris flow under the powerful impact in the sliding process of landslide, then caused larger disaster area. Accumulation range and shape of simulation and actual measurement are the similar.
2017, 25(s1): 407-414.
Due to the characteristics like high and steep slope and its strong concealment, the accurate identification of dangerous rocks in high and steep slope has always been confronting with great difficulty. The author uses technology like unmanned aerial vehicle aerial photography and Agisoft PhotoScan to establish the dioramas and three-dimentional data of the rock mass in high and steep slopes. Based on the principle that three points which are non-collinear can specify a plane, the author uses Visual Basic language to write a program in order to complete the calculation of structual plane's occurrence, thereby a algorithm is formed to accurately indetify the structual plane of rock mass and massively and rapidly extract point cloud data to calclulate the geometrical characteristics of structual plane's occurrence. And a typical rock mass slope in Zhejiang Immortals scenery area is selected as a case to analyze. After confirming the dangerous rocks, the motion features of the unstable rocks are predicted and analyzed with the assist of rolling rocks simulation software. The results show that once stones fall from A-D they will all hit directly in travel line, therefore cause great threaten to the security of travelers. It is advisable to take engineering measures as soon as possible to reduce risk levels.
Due to the characteristics like high and steep slope and its strong concealment, the accurate identification of dangerous rocks in high and steep slope has always been confronting with great difficulty. The author uses technology like unmanned aerial vehicle aerial photography and Agisoft PhotoScan to establish the dioramas and three-dimentional data of the rock mass in high and steep slopes. Based on the principle that three points which are non-collinear can specify a plane, the author uses Visual Basic language to write a program in order to complete the calculation of structual plane's occurrence, thereby a algorithm is formed to accurately indetify the structual plane of rock mass and massively and rapidly extract point cloud data to calclulate the geometrical characteristics of structual plane's occurrence. And a typical rock mass slope in Zhejiang Immortals scenery area is selected as a case to analyze. After confirming the dangerous rocks, the motion features of the unstable rocks are predicted and analyzed with the assist of rolling rocks simulation software. The results show that once stones fall from A-D they will all hit directly in travel line, therefore cause great threaten to the security of travelers. It is advisable to take engineering measures as soon as possible to reduce risk levels.
2017, 25(s1): 415-420.
At home and abroad for cast-in-place piles of underwater concrete quality inspecting method are many, such as the low strain reflected wave method, high strain dynamic test method, the single pile vertical static load compression test, core method, ultrasonic transmission method et al. Each method has its scope of application and limitations. Ultrasonic transmission method and compared with other methods, this method is of high precision, intuitive and reliable results, is suitable for large diameter pile, the pile of super-long pile testing, therefore, in cast-in-place piles integrity testing, has been widely used, especially in the bridge piles, extend, almost all use the sound wave transmission method of large diameter pile detection. In this paper, a construction site of large diameter piles of ultrasonic transmission method is investigated, through waveform and image contrast, better ltrasonic transmission method was verified test super-long and large diameter effect of these measures. In this paper, a construction site of large diameter piles of ultrasonic transmission method is investigated, through waveform and image contrast, better ultrasonic transmission method was verified test super-long and large diameter effect of these measures.
At home and abroad for cast-in-place piles of underwater concrete quality inspecting method are many, such as the low strain reflected wave method, high strain dynamic test method, the single pile vertical static load compression test, core method, ultrasonic transmission method et al. Each method has its scope of application and limitations. Ultrasonic transmission method and compared with other methods, this method is of high precision, intuitive and reliable results, is suitable for large diameter pile, the pile of super-long pile testing, therefore, in cast-in-place piles integrity testing, has been widely used, especially in the bridge piles, extend, almost all use the sound wave transmission method of large diameter pile detection. In this paper, a construction site of large diameter piles of ultrasonic transmission method is investigated, through waveform and image contrast, better ltrasonic transmission method was verified test super-long and large diameter effect of these measures. In this paper, a construction site of large diameter piles of ultrasonic transmission method is investigated, through waveform and image contrast, better ultrasonic transmission method was verified test super-long and large diameter effect of these measures.
2017, 25(s1): 421-427.
Because of the high degree of heterogeneity and complexity of karst aquifer media, there are many uncertainties in the tunnel construction. This paper takes the proposed Qiganshan Tunnel of Chengkai Expressway in Chengkou county as an example, using on-line tracer technique, getting high-resolution tracer data, combining with the method of quantitative interpretation to analyze the potential flow direction and flow field of karst groundwater in the tunnel area. By putting the tracer into the borehole to carry out work, the test results identify the relation between the groundwater of the testsite and outlets of several underground rivers. This result could be a useful tool to identify the karst underground water ridge and calculate the hydro-stress gradient of the tunnel area. This test greatly improves the precision of hydrogeology investigation in the tunnel area. By this example, it is indicated that the on-line tracer technique is of great value for popularization and application in the study of aquifer media and its related exploration in karst areas of Southwest China.
Because of the high degree of heterogeneity and complexity of karst aquifer media, there are many uncertainties in the tunnel construction. This paper takes the proposed Qiganshan Tunnel of Chengkai Expressway in Chengkou county as an example, using on-line tracer technique, getting high-resolution tracer data, combining with the method of quantitative interpretation to analyze the potential flow direction and flow field of karst groundwater in the tunnel area. By putting the tracer into the borehole to carry out work, the test results identify the relation between the groundwater of the testsite and outlets of several underground rivers. This result could be a useful tool to identify the karst underground water ridge and calculate the hydro-stress gradient of the tunnel area. This test greatly improves the precision of hydrogeology investigation in the tunnel area. By this example, it is indicated that the on-line tracer technique is of great value for popularization and application in the study of aquifer media and its related exploration in karst areas of Southwest China.
2017, 25(s1): 428-433.
CO2 capture, utilization and storage(CCUS) is one of the important technical ways for greenhouse gas reduction. The sealing capacity of caprocks is an important index for screening CO2 storage site, which has one ticket veto. Based on the knowledge of sealing mechanism, the physical sealing capacity of caprocks is defined in the context of CCUS.According to the assessment thought of oil/gas reservoirs, the maximum CO2 plume height is chosen as the quantitative index for sealing capacity assessment. In consideration of mechanical equilibrium between CO2 buoyancy and capillary pressure of caprocks, the maximum CO2 plume height is calculated for Jilin oil field as a case study. This paper provides a way for quantitative assessment of effective CO2 capacity before the CO2 breakthrough.
CO2 capture, utilization and storage(CCUS) is one of the important technical ways for greenhouse gas reduction. The sealing capacity of caprocks is an important index for screening CO2 storage site, which has one ticket veto. Based on the knowledge of sealing mechanism, the physical sealing capacity of caprocks is defined in the context of CCUS.According to the assessment thought of oil/gas reservoirs, the maximum CO2 plume height is chosen as the quantitative index for sealing capacity assessment. In consideration of mechanical equilibrium between CO2 buoyancy and capillary pressure of caprocks, the maximum CO2 plume height is calculated for Jilin oil field as a case study. This paper provides a way for quantitative assessment of effective CO2 capacity before the CO2 breakthrough.
2017, 25(s1): 434-439.
Large-scale accumulation slopes are widespread in the hydropower engineering constructions. The stability of accumulation slope has a great impact on the feasibility of the project and the safe operation. The accumulation horizon of complex composition has significant randomness and the parameters have variability. These characteristics make some uncertainty in the stability analysis of the stability of this type of slope. Based on probability theory, we use K-S test method to verify the distribution type of the physical and mechanical parameters. This method can reduce the influence of errors caused by artificial assumption. And sample the parameters respectively tested by K-S test method and artificial assumption method to obtain the state function and get the safety factor and reliability by using Monte Carlo Method. Comparison of two distribution type test methods, the K-S test method combined with Monte-Carlo method can improve the accuracy of reliability analysis effectively.
Large-scale accumulation slopes are widespread in the hydropower engineering constructions. The stability of accumulation slope has a great impact on the feasibility of the project and the safe operation. The accumulation horizon of complex composition has significant randomness and the parameters have variability. These characteristics make some uncertainty in the stability analysis of the stability of this type of slope. Based on probability theory, we use K-S test method to verify the distribution type of the physical and mechanical parameters. This method can reduce the influence of errors caused by artificial assumption. And sample the parameters respectively tested by K-S test method and artificial assumption method to obtain the state function and get the safety factor and reliability by using Monte Carlo Method. Comparison of two distribution type test methods, the K-S test method combined with Monte-Carlo method can improve the accuracy of reliability analysis effectively.
2017, 25(s1): 440-444.
In order to reduce the influence of surface roughness on the test result, rectangular section probe of T-bar test is presented. Assuming that soft clay strength obeys the Tresca yield condition and the resistance of rectangular probe is equal to the sum of that of single level and vertical plate without thickness, the approximate solution of the coefficient of the resistance of rectangular section probes is obtained. A comparison between rectangle section probe and oval section probe is made in terms of mechanical characteristics, deformation and strength. Results show that rectangular probe is better than oval cross section probes in those aspects. Rectangular cross section probe is a kind of applicable test probe.
In order to reduce the influence of surface roughness on the test result, rectangular section probe of T-bar test is presented. Assuming that soft clay strength obeys the Tresca yield condition and the resistance of rectangular probe is equal to the sum of that of single level and vertical plate without thickness, the approximate solution of the coefficient of the resistance of rectangular section probes is obtained. A comparison between rectangle section probe and oval section probe is made in terms of mechanical characteristics, deformation and strength. Results show that rectangular probe is better than oval cross section probes in those aspects. Rectangular cross section probe is a kind of applicable test probe.
2017, 25(s1): 445-451.
Based on the facts that BP neural networks have some flaws, such as characteristics of low efficiency and low accuracy. A new BP neural networks was put forward to forecast the surface settlement of pits, which depend on Simulated Annealing. The kernel functions was determined by the theory of optimization of overall situation, which could improve the efficiency and accuracy of BP neural networks. According to the typical pits excavation cases in Shanghai, the SA-BP neural networks that based on Simulated Annealing was built to forecast the surface settlement of pits. And the result was juxtaposed with normal distribution and skew distribution and the results of statistical analysis. The result shown that the results obtained by SA-BP neural networks were closer to reality than others, the error was low. And the method can be used to analysis and forecast the surface settlement of pits.
Based on the facts that BP neural networks have some flaws, such as characteristics of low efficiency and low accuracy. A new BP neural networks was put forward to forecast the surface settlement of pits, which depend on Simulated Annealing. The kernel functions was determined by the theory of optimization of overall situation, which could improve the efficiency and accuracy of BP neural networks. According to the typical pits excavation cases in Shanghai, the SA-BP neural networks that based on Simulated Annealing was built to forecast the surface settlement of pits. And the result was juxtaposed with normal distribution and skew distribution and the results of statistical analysis. The result shown that the results obtained by SA-BP neural networks were closer to reality than others, the error was low. And the method can be used to analysis and forecast the surface settlement of pits.
2017, 25(s1): 452-457.
Xianshuihe fault zone is a strong left-lateral strike-slip fault, with large strength and high frequency activity, exposes millions of people to potential risk from strong motion and earthquake-induced secondary geological disasters in southwest China. The seismicity on this faults zone has the typical features of characteristic earthquakes and obvious active faults segmentation. In this work base on characteristic earthquake model in each active fault segmentation, seismic time history and peak value of strong ground motions on near field observation points is predicted by stochastic finite-fault source model. Parameters of source model composed by magnitude of characteristic earthquake, geometric dimensioning of characteristic rupture plane, the stress drop and so on. Finally, the prediction map of ground motion made by characteristic earthquake near the whole fault zone is obtained. Research technology and methods have important implications for China's earthquake disaster reduction work, and benefit innovation and development of China's seismic zoning.
Xianshuihe fault zone is a strong left-lateral strike-slip fault, with large strength and high frequency activity, exposes millions of people to potential risk from strong motion and earthquake-induced secondary geological disasters in southwest China. The seismicity on this faults zone has the typical features of characteristic earthquakes and obvious active faults segmentation. In this work base on characteristic earthquake model in each active fault segmentation, seismic time history and peak value of strong ground motions on near field observation points is predicted by stochastic finite-fault source model. Parameters of source model composed by magnitude of characteristic earthquake, geometric dimensioning of characteristic rupture plane, the stress drop and so on. Finally, the prediction map of ground motion made by characteristic earthquake near the whole fault zone is obtained. Research technology and methods have important implications for China's earthquake disaster reduction work, and benefit innovation and development of China's seismic zoning.
2017, 25(s1): 458-462.
The southeast of the Qinghai-Tibet Plateau in China, contains the richest hydro-energy resource. There is an urgent need for identification and monitoring of the large number of landslides developing in Xiluodu reservoir area. This article makes it possible to observe the deformation of a large landslide before and after impoundment using archived ALOS PALSAR,ENVISAT ASAR and recent programmed TerraSAR-X synthetic aperture radar data based on InSAR Technology. Based on the geological background and field investigation, the deformation characteristics and sliding mode of the landslide are revealed. (1)The landslide is an ancient landslide, and the deformation area today is in front of the accumulation body. It had obvious deformation before the impoundment, and the maximum deformation is located in the middle of the sliding body with main line- of -slope deformation. The rear area of the landslide is a material reduction area, with main vertical deformation. According to the interference phase of the ascending and descending data, the sliding mode is considered as a push type. (2)D-InSAR results show that the slope develops three value ladders after the impoundment, where has cracks and raised paths through fields, and the sliding mode is a pull type. (3)The groundwater activity is strong in the study area, and the field survey shows that the underground water level is high. The sliding surface has been connected before the filling. Due to the rising reservoir water level, saturated rock mass in the central area of the landslide and moist surface structure, which decrease the anti-sliding ability, and the landslide sliding mode change from the push-type to the pull-type.
The southeast of the Qinghai-Tibet Plateau in China, contains the richest hydro-energy resource. There is an urgent need for identification and monitoring of the large number of landslides developing in Xiluodu reservoir area. This article makes it possible to observe the deformation of a large landslide before and after impoundment using archived ALOS PALSAR,ENVISAT ASAR and recent programmed TerraSAR-X synthetic aperture radar data based on InSAR Technology. Based on the geological background and field investigation, the deformation characteristics and sliding mode of the landslide are revealed. (1)The landslide is an ancient landslide, and the deformation area today is in front of the accumulation body. It had obvious deformation before the impoundment, and the maximum deformation is located in the middle of the sliding body with main line- of -slope deformation. The rear area of the landslide is a material reduction area, with main vertical deformation. According to the interference phase of the ascending and descending data, the sliding mode is considered as a push type. (2)D-InSAR results show that the slope develops three value ladders after the impoundment, where has cracks and raised paths through fields, and the sliding mode is a pull type. (3)The groundwater activity is strong in the study area, and the field survey shows that the underground water level is high. The sliding surface has been connected before the filling. Due to the rising reservoir water level, saturated rock mass in the central area of the landslide and moist surface structure, which decrease the anti-sliding ability, and the landslide sliding mode change from the push-type to the pull-type.
2017, 25(s1): 463-469.
In the process of reclaiming the backfill in the steep slope, due to the high compressibility and gravity of the ordinary backfill, it has a great adverse effect on the stability of the steep slope. Taking the slope of a highway in Longgang of Shenzhen as an example, the Abaqus software was used to simulate the stress of steep slope subgrade and retaining wall, and the steep slope roadbed is divided into two parts:backfill light and ordinary backfill. The stability of the slope soil and the retaining wall, and the stress and strain and displacement of the wall are analyzed and compared. The simulation results show that the soils of the slope and the soil at the junction of the retaining wall and the soil are in the form of ordinary backfill, and the two soils are destroyed. In the backfill condition, the plastic strain zone does not penetrate the entire sliding surface. The maximum stress of the steep slope embankment retaining wall is 165kPa in the normal filling condition, the wall displacement is 100.3mm, the anti-sliding stability coefficient and the anti-overturning stability coefficient are 1.45 and 2.51. The maximum stress of the soil is 133kPa, the overall displacement is reduced by about 87mm, and the anti-sliding stability coefficient and anti-overturning stability coefficient are 1.64 and 3.01 respectively. According to the comparison and analysis of the simulation results in two kinds of working conditions, it is shown that the application of lightweight soil in steep slope subgrade backfill can improve the safety of the slope and reduce the pressure of the retaining structure obviously compared with the conventional filling, and it has a high engineering application value.
In the process of reclaiming the backfill in the steep slope, due to the high compressibility and gravity of the ordinary backfill, it has a great adverse effect on the stability of the steep slope. Taking the slope of a highway in Longgang of Shenzhen as an example, the Abaqus software was used to simulate the stress of steep slope subgrade and retaining wall, and the steep slope roadbed is divided into two parts:backfill light and ordinary backfill. The stability of the slope soil and the retaining wall, and the stress and strain and displacement of the wall are analyzed and compared. The simulation results show that the soils of the slope and the soil at the junction of the retaining wall and the soil are in the form of ordinary backfill, and the two soils are destroyed. In the backfill condition, the plastic strain zone does not penetrate the entire sliding surface. The maximum stress of the steep slope embankment retaining wall is 165kPa in the normal filling condition, the wall displacement is 100.3mm, the anti-sliding stability coefficient and the anti-overturning stability coefficient are 1.45 and 2.51. The maximum stress of the soil is 133kPa, the overall displacement is reduced by about 87mm, and the anti-sliding stability coefficient and anti-overturning stability coefficient are 1.64 and 3.01 respectively. According to the comparison and analysis of the simulation results in two kinds of working conditions, it is shown that the application of lightweight soil in steep slope subgrade backfill can improve the safety of the slope and reduce the pressure of the retaining structure obviously compared with the conventional filling, and it has a high engineering application value.
2017, 25(s1): 470-477.
The reliability of FEM strength reduction in slope stability analysis and its result evaluation are the key factors that influence the engineering application of this method. Based on the ultimate bearing capacity problem of foundation and the slope stability benchmark examples of Australian Computer Application Association(ACADS). This paper deals with the reliability, the slope failure criterion and result evaluation of FEM strength reduction in slope stability analysis. A result evaluation method based on the ratio of width and length of the plastic zone b/L was proposed. Results show that the FEM strength reduction method is effective in the condition of sufficient and reasonable mesh density. And there is no significant difference between different slope failure criterions in this condition, while the plastic strain zone connection criterion is the most objective criterion. The results show that the relevance are very high between the safety factor and the ratio of width and length of the plastic zone b/L.The smaller value of this ratio, the higher precision of the safety factor. And the relative error of safety factor is less than 5%when the ratio b/L is less than 0.05. If the slip mechanism and the slip face could be determined from the equivalent plastic strain distribution, the difference of safety factor from that of finer mesh grid is less than 5% and the accuracy of the FEM strength reduction method is sufficient.
The reliability of FEM strength reduction in slope stability analysis and its result evaluation are the key factors that influence the engineering application of this method. Based on the ultimate bearing capacity problem of foundation and the slope stability benchmark examples of Australian Computer Application Association(ACADS). This paper deals with the reliability, the slope failure criterion and result evaluation of FEM strength reduction in slope stability analysis. A result evaluation method based on the ratio of width and length of the plastic zone b/L was proposed. Results show that the FEM strength reduction method is effective in the condition of sufficient and reasonable mesh density. And there is no significant difference between different slope failure criterions in this condition, while the plastic strain zone connection criterion is the most objective criterion. The results show that the relevance are very high between the safety factor and the ratio of width and length of the plastic zone b/L.The smaller value of this ratio, the higher precision of the safety factor. And the relative error of safety factor is less than 5%when the ratio b/L is less than 0.05. If the slip mechanism and the slip face could be determined from the equivalent plastic strain distribution, the difference of safety factor from that of finer mesh grid is less than 5% and the accuracy of the FEM strength reduction method is sufficient.
2017, 25(s1): 478-483.
In this study, a new kind of structure quantitative parameter based on strain energy is proposed to describe soil structure on the basis of research of related structure quantitative parameters. Undisturbed and remolded loess in Chifeng City of China was investigated by conventional triaxial test under different confining pressures, and stress-strain curves were drawn though the test. The structure parameter based on strain energy was calculated with the comparison of the structure parameter based on stress difference. And then the construction features of Chifeng loess were analyzed to study the applicability of this new structure parameter. The results show that the two kinds of structure parameters both range from 1.5 to 2.0,which is irrelevant to the confining pressures. The new structure parameter based on strain energy is suitable to describe soil structure in actual application.
In this study, a new kind of structure quantitative parameter based on strain energy is proposed to describe soil structure on the basis of research of related structure quantitative parameters. Undisturbed and remolded loess in Chifeng City of China was investigated by conventional triaxial test under different confining pressures, and stress-strain curves were drawn though the test. The structure parameter based on strain energy was calculated with the comparison of the structure parameter based on stress difference. And then the construction features of Chifeng loess were analyzed to study the applicability of this new structure parameter. The results show that the two kinds of structure parameters both range from 1.5 to 2.0,which is irrelevant to the confining pressures. The new structure parameter based on strain energy is suitable to describe soil structure in actual application.
2017, 25(s1): 484-489.
As a new way to deal with liquefiable foundation, resonant compaction method has already been applied to practical engineering. For the further study of treatment effect on liquefiable ground using resonant compaction method and the law of energy transfer in the resonance state, this paper mainly analyzes two different conditions of silts and sands by using laboratory model test. In this paper, the authors arrange sensors in the soil to monitor the changes of vibratory acceleration in soil layer. The test results show that the compactness of silts and sands foundation treated by resonant compaction method is greatly improved. At the same time, the effect of sands foundation is better than silts foundation. The effective reinforcement range of silts foundation using resonant compaction method is about 20cm. The effective reinforcement range of sands foundation using resonant compaction method is 20~30cm. Along the transverse direction, the energy transmission of silts and sands foundation is decreasing. Along the longitudinal direction, the energy transfer of silts foundation is the largest in the lower soil layer, is second in the upper soil layer, is the smallest in the middle soil layer. The energy transfer of sands foundation is the largest in the upper soil layer, is second in the lower soil layer, is the smallest in the middle soil layer.
As a new way to deal with liquefiable foundation, resonant compaction method has already been applied to practical engineering. For the further study of treatment effect on liquefiable ground using resonant compaction method and the law of energy transfer in the resonance state, this paper mainly analyzes two different conditions of silts and sands by using laboratory model test. In this paper, the authors arrange sensors in the soil to monitor the changes of vibratory acceleration in soil layer. The test results show that the compactness of silts and sands foundation treated by resonant compaction method is greatly improved. At the same time, the effect of sands foundation is better than silts foundation. The effective reinforcement range of silts foundation using resonant compaction method is about 20cm. The effective reinforcement range of sands foundation using resonant compaction method is 20~30cm. Along the transverse direction, the energy transmission of silts and sands foundation is decreasing. Along the longitudinal direction, the energy transfer of silts foundation is the largest in the lower soil layer, is second in the upper soil layer, is the smallest in the middle soil layer. The energy transfer of sands foundation is the largest in the upper soil layer, is second in the lower soil layer, is the smallest in the middle soil layer.
2017, 25(s1): 490-495.
Aiming at the impact of pollutants on the aeration zone environment, this article establish the hydrogeological model by Hydrus-1D software and conduct numerical simulation of contaminant transport in aeration zone with numerical simulation method by taking the COD of a power plant as the predictor. The simulation results reflect the rules of contaminant transport and the conclusion show that under the condition that contaminant discharge is simplified as a constant point source, the pollution in aeration zone move downward with time, the closer to the infiltration point position, pollutant concentration is higher; the farther to the infiltration point position, the lower the concentration of pollutants. In soil profile, along with the depth increase, the pollutant concentration change rate increase.
Aiming at the impact of pollutants on the aeration zone environment, this article establish the hydrogeological model by Hydrus-1D software and conduct numerical simulation of contaminant transport in aeration zone with numerical simulation method by taking the COD of a power plant as the predictor. The simulation results reflect the rules of contaminant transport and the conclusion show that under the condition that contaminant discharge is simplified as a constant point source, the pollution in aeration zone move downward with time, the closer to the infiltration point position, pollutant concentration is higher; the farther to the infiltration point position, the lower the concentration of pollutants. In soil profile, along with the depth increase, the pollutant concentration change rate increase.
2017, 25(s1): 496-502.
The in-situ hydrogeological test is a variety of experiments which is indispensable in a hydrogeological investigation in order to obtain the hydrogeological parameters and find out the groundwater movement conditions. In recent years, human activities and urban development changed the hydrogeological conditions of riverbed in Yongding River, followed by the changed hydrogeological parameters. In this paper, different hydrogeological parameters of the Yongding River bed are obtained by six double-ring infiltration tests, two percolation pit tests, four pumping tests. It was found that, the vertical average permeability coefficients of the exterior and the middle of the surface river bed are 2.155md-1, 1.469md-1, 0.557md-1 and 0.3865md-1,respectively. The permeability coefficients of the deep layers of the Lianshi Lake and the thermal power plant were 5.92md-1, 2.68md-1.The permeability coefficients of Zhaocun, Efang, Lugou Bridge and Lianshi Road were 10md-1, 28md-1, 70md-1, 124md-1,respectively. According the dispersion test conducted in the section of the Lugou Bridge of Yongding River, the longitudinal dispersion coefficient(DL),actual groundwater flowrate(U) and dispersion degree(a) are 0.772m2h-1, 0.146mh-1 and 5.287m, respectively. The acquisition of hydrogeological parameters under the present conditions provides an important basis for groundwater resources calculation and evaluation, groundwater numerical simulation and forecasting, groundwater exploitation, protection and scientific management, and provides support for the construction of the green ecological development zone in Yongding River.
The in-situ hydrogeological test is a variety of experiments which is indispensable in a hydrogeological investigation in order to obtain the hydrogeological parameters and find out the groundwater movement conditions. In recent years, human activities and urban development changed the hydrogeological conditions of riverbed in Yongding River, followed by the changed hydrogeological parameters. In this paper, different hydrogeological parameters of the Yongding River bed are obtained by six double-ring infiltration tests, two percolation pit tests, four pumping tests. It was found that, the vertical average permeability coefficients of the exterior and the middle of the surface river bed are 2.155md-1, 1.469md-1, 0.557md-1 and 0.3865md-1,respectively. The permeability coefficients of the deep layers of the Lianshi Lake and the thermal power plant were 5.92md-1, 2.68md-1.The permeability coefficients of Zhaocun, Efang, Lugou Bridge and Lianshi Road were 10md-1, 28md-1, 70md-1, 124md-1,respectively. According the dispersion test conducted in the section of the Lugou Bridge of Yongding River, the longitudinal dispersion coefficient(DL),actual groundwater flowrate(U) and dispersion degree(a) are 0.772m2h-1, 0.146mh-1 and 5.287m, respectively. The acquisition of hydrogeological parameters under the present conditions provides an important basis for groundwater resources calculation and evaluation, groundwater numerical simulation and forecasting, groundwater exploitation, protection and scientific management, and provides support for the construction of the green ecological development zone in Yongding River.
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