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Editor Work2015 Vol. 23, No. 3
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2015, 23(3): 361-372.
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Data acquisition and inventory of landslide dams are the foundation of their regional research. Himalaya is located in the southwest of China. A number of landslide dams occurred here and brought serious property losses, as well as undesirable international influence. This paper is based on Remote Sensing and Geographic Information technologies. It obtains 136 landslide dams. Their spatial location, basic attributes and geometry features are obtained by RS image information extraction and field investigation. Then the landslide dams inventory is finished. It is found that the landslide dams are mainly caused by landslide, collapse and debris flow. The dams have the regional feature of concentrating distribution among Milin, Zhada, Jiacha, Cuona, Longzi and Longxian. Calculating information values of influence factors, it is found that landslide dam susceptibility increases at first, then decreases with the increase of elevation, slope and seismic acceleration. It decreases at first, then increases with the increase of seismic dot density. It also increases with the increase of tectonic line density, and decreases with the increase of distance to river. West slope, high mountain, Langxian tectonic melange and hard rock of lithology, High Himalaya tectonic region and Yarlu Zangbo tectonic region are the favorable factors of landslide dam formation. In view to the information values, among all the influence factors, elevation, geomorphic type, lithological characteristics and seismic dot density are more closely related to landslide dam susceptibility. As to the geometry features, there is a typical power function relation between dam length and dam area, as well as landslide area and dam area. Nevertheless, the relations between other geometry parameters are not striking.
Data acquisition and inventory of landslide dams are the foundation of their regional research. Himalaya is located in the southwest of China. A number of landslide dams occurred here and brought serious property losses, as well as undesirable international influence. This paper is based on Remote Sensing and Geographic Information technologies. It obtains 136 landslide dams. Their spatial location, basic attributes and geometry features are obtained by RS image information extraction and field investigation. Then the landslide dams inventory is finished. It is found that the landslide dams are mainly caused by landslide, collapse and debris flow. The dams have the regional feature of concentrating distribution among Milin, Zhada, Jiacha, Cuona, Longzi and Longxian. Calculating information values of influence factors, it is found that landslide dam susceptibility increases at first, then decreases with the increase of elevation, slope and seismic acceleration. It decreases at first, then increases with the increase of seismic dot density. It also increases with the increase of tectonic line density, and decreases with the increase of distance to river. West slope, high mountain, Langxian tectonic melange and hard rock of lithology, High Himalaya tectonic region and Yarlu Zangbo tectonic region are the favorable factors of landslide dam formation. In view to the information values, among all the influence factors, elevation, geomorphic type, lithological characteristics and seismic dot density are more closely related to landslide dam susceptibility. As to the geometry features, there is a typical power function relation between dam length and dam area, as well as landslide area and dam area. Nevertheless, the relations between other geometry parameters are not striking.
2015, 23(3): 373-382.
The article is based on field survey, and data of remote sensing interpretation. It elaborates genetic mechanism and characteristics of Dongyuege river debris flow hazards. It analyses the geological environmental background. The terrain conditions are long distance, large gradient and narrow canyon and straight channel. It provides a powerful terrain condition for the occurrence of debris flow. There are a lot of loose deposits of upstream. They provide sufficient material sources for the occurrence of debris flow. The debris flow lasted 2273 second. The flow rate was 4.62ms-1.The seepage was 1008m3s-1.Mizoguchi formed in a length of about 300m, and a maximum width of about 400m of the alluvial fan. The total debris volume was about 60.5104m3. The total solid volume of a single event was of 41.95104m3. The fluid was thick paste. The fluid had straight and strong uplift force and had structural movement without vertical exchange. The fluid had obvious characteristics that drag reduction and showers movement. The debris flow density was 2.04gcm-3.It was a large viscous debris flow. The corners ultra of debris flow was quite obvious from mizoguchi 2.5km. Its height was 4.1m. The debris flow overall impact was 64.01kN.The single rock block maximum impact force was 491.27 tf. Dongyuege debris flow had the features of high drop, large gradient, narrow canyons, gross volume, high-speed, and long-distance. It also had a characteristic that was hidden, sudden and devastating. It is a typical high debris flow. Analysing the debris flow mechanism and movement characteristics can provide a scientific basis for the early identification, monitoring warning and risk evaluation of the entire Nujiang River Basin, as well as the southwest mountains and canyons area high debris flow.
The article is based on field survey, and data of remote sensing interpretation. It elaborates genetic mechanism and characteristics of Dongyuege river debris flow hazards. It analyses the geological environmental background. The terrain conditions are long distance, large gradient and narrow canyon and straight channel. It provides a powerful terrain condition for the occurrence of debris flow. There are a lot of loose deposits of upstream. They provide sufficient material sources for the occurrence of debris flow. The debris flow lasted 2273 second. The flow rate was 4.62ms-1.The seepage was 1008m3s-1.Mizoguchi formed in a length of about 300m, and a maximum width of about 400m of the alluvial fan. The total debris volume was about 60.5104m3. The total solid volume of a single event was of 41.95104m3. The fluid was thick paste. The fluid had straight and strong uplift force and had structural movement without vertical exchange. The fluid had obvious characteristics that drag reduction and showers movement. The debris flow density was 2.04gcm-3.It was a large viscous debris flow. The corners ultra of debris flow was quite obvious from mizoguchi 2.5km. Its height was 4.1m. The debris flow overall impact was 64.01kN.The single rock block maximum impact force was 491.27 tf. Dongyuege debris flow had the features of high drop, large gradient, narrow canyons, gross volume, high-speed, and long-distance. It also had a characteristic that was hidden, sudden and devastating. It is a typical high debris flow. Analysing the debris flow mechanism and movement characteristics can provide a scientific basis for the early identification, monitoring warning and risk evaluation of the entire Nujiang River Basin, as well as the southwest mountains and canyons area high debris flow.
2015, 23(3): 383-393.
Many secondary natural geological disasters are caused by Lushan MS7.0 and Ludian MS6.3 earthquake. Some scholars consider the disasters may be associated with topographic amplification effect of seismic waves. But it is still lack of a large number of slope seismic response data to verify such hypothesis. The strong monitoring site of Luding Lengzhuguan is located on both sides of the Lengzhuguan valley, a tributary of the Dadu River and situated to the right back of the river. Tunnels excavated in different parts of the slope are used to place earthquake monitoring instruments on both sides of the valley. The instruments monitored the Kangding MS6.3 earthquake on November 22, 2014 in Sichuan, China. The earthquake monitoring data show the follows:(1)Reference to Kangding Guzan strong earthquake monitoring station of the main shock records(its horizontal and vertical PGA components are 16.4 and 15.7gal, respectively),the horizontal and vertical PGA amplification factors of the 1# monitoring site on the top of the peninsular terrain on the right bank reach 10.6-11.5 and 7.1,respectively. The Arias Intensity of the 1# monitoring site is largest. The Predominant Period was concentrated in the low-frequency, and horizontal to vertical spectral ratio reaches 11.1. The horizontal and vertical PGA amplification factors of the 2# monitoring site in the middle reach 4.3-5.0 and 2.3,respectively. Both of the Arias Intensity and horizontal to vertical spectral ratio were smaller than those at 1#.(2)The slope terrain variation on the left bank is small and the record of PGA is low.the result at the 5# monitoring site is enlarged obviously. The horizontal and vertical PGA amplification factors are 2.1-4.5 and 1.7-2.3,respectively. The monitoring sites on the left bank have several Predominant Period. The amplification effect is more prominent at high-frequency. The Arias Intensity of each is smaller than the right monitoring sites.(3)Ground motion topographic amplification effect in the nearly linear slope part is weak(6# and 7#).Some monitoring sites are narrowed to varying degrees. The amplification factor of the outside monitoring site is larger than the level depth of the inside monitoring site. Studies suggest that ground motion topographic amplification effect is obvious on both sides of the Lengzhuguan valley. The topography amplification effect of the peninsular terrain on the right bank is stronger than that on the left nearly linear slope. Furthermore, the amplification factor on the top of the peninsular terrain on the right bank is bigger than that on the middle. The topography amplification effect on the part of slope break is obvious and the part of nearly linear slope is weaker. According to direction of seismic wave propagation, the Lengzhuguan monitoring station is at the back side for Kangding earthquake. It is contrary for Lushan earthquake. Comparison of the results between the seismic data of Kangding earthquake and Lushan earthquake, it is found that the PGA amplification coefficients of each monitoring site during Kangding earthquake is bigger than those at Lushan earthquake. One result reaches to 5 times.
Many secondary natural geological disasters are caused by Lushan MS7.0 and Ludian MS6.3 earthquake. Some scholars consider the disasters may be associated with topographic amplification effect of seismic waves. But it is still lack of a large number of slope seismic response data to verify such hypothesis. The strong monitoring site of Luding Lengzhuguan is located on both sides of the Lengzhuguan valley, a tributary of the Dadu River and situated to the right back of the river. Tunnels excavated in different parts of the slope are used to place earthquake monitoring instruments on both sides of the valley. The instruments monitored the Kangding MS6.3 earthquake on November 22, 2014 in Sichuan, China. The earthquake monitoring data show the follows:(1)Reference to Kangding Guzan strong earthquake monitoring station of the main shock records(its horizontal and vertical PGA components are 16.4 and 15.7gal, respectively),the horizontal and vertical PGA amplification factors of the 1# monitoring site on the top of the peninsular terrain on the right bank reach 10.6-11.5 and 7.1,respectively. The Arias Intensity of the 1# monitoring site is largest. The Predominant Period was concentrated in the low-frequency, and horizontal to vertical spectral ratio reaches 11.1. The horizontal and vertical PGA amplification factors of the 2# monitoring site in the middle reach 4.3-5.0 and 2.3,respectively. Both of the Arias Intensity and horizontal to vertical spectral ratio were smaller than those at 1#.(2)The slope terrain variation on the left bank is small and the record of PGA is low.the result at the 5# monitoring site is enlarged obviously. The horizontal and vertical PGA amplification factors are 2.1-4.5 and 1.7-2.3,respectively. The monitoring sites on the left bank have several Predominant Period. The amplification effect is more prominent at high-frequency. The Arias Intensity of each is smaller than the right monitoring sites.(3)Ground motion topographic amplification effect in the nearly linear slope part is weak(6# and 7#).Some monitoring sites are narrowed to varying degrees. The amplification factor of the outside monitoring site is larger than the level depth of the inside monitoring site. Studies suggest that ground motion topographic amplification effect is obvious on both sides of the Lengzhuguan valley. The topography amplification effect of the peninsular terrain on the right bank is stronger than that on the left nearly linear slope. Furthermore, the amplification factor on the top of the peninsular terrain on the right bank is bigger than that on the middle. The topography amplification effect on the part of slope break is obvious and the part of nearly linear slope is weaker. According to direction of seismic wave propagation, the Lengzhuguan monitoring station is at the back side for Kangding earthquake. It is contrary for Lushan earthquake. Comparison of the results between the seismic data of Kangding earthquake and Lushan earthquake, it is found that the PGA amplification coefficients of each monitoring site during Kangding earthquake is bigger than those at Lushan earthquake. One result reaches to 5 times.
2015, 23(3): 394-400.
To the creeping slope, accurate determination of creep segment and lock segment is the basement of stability evaluating and evolution trend predicting. This paper examines a deformable body of bending rock bank slope in southwest mountainous of China. The examination is based on the comprehensive analysis on the slope engineering geological conditions. The field investigation, ground displacement monitoring, drilling, adit, underground displacement monitoring and geophysical prospecting are used to detecting the structural characteristics of the bank slope. Then, the ground and underground deformation zoning is taking to the slope. The present stability status is examined. The locked segment and creeping segment are divided accordingly. The results show the follows.(1)The bank slope has occurred bending and toppling during the river bed scour. The depth of bending fracture plane is between 20m and 80m.(2)Creeping segment is located in middle-anterior and posterior of the slope. The locked segment is located in the middle of the slope. These results can be used to stability evaluating of these slopes. They have some reference meaning to investigation method and comprehensive analysis of other creeping slopes.
To the creeping slope, accurate determination of creep segment and lock segment is the basement of stability evaluating and evolution trend predicting. This paper examines a deformable body of bending rock bank slope in southwest mountainous of China. The examination is based on the comprehensive analysis on the slope engineering geological conditions. The field investigation, ground displacement monitoring, drilling, adit, underground displacement monitoring and geophysical prospecting are used to detecting the structural characteristics of the bank slope. Then, the ground and underground deformation zoning is taking to the slope. The present stability status is examined. The locked segment and creeping segment are divided accordingly. The results show the follows.(1)The bank slope has occurred bending and toppling during the river bed scour. The depth of bending fracture plane is between 20m and 80m.(2)Creeping segment is located in middle-anterior and posterior of the slope. The locked segment is located in the middle of the slope. These results can be used to stability evaluating of these slopes. They have some reference meaning to investigation method and comprehensive analysis of other creeping slopes.
2015, 23(3): 401-407.
Displacement-time curves represent the status and relative stability of landslide deformation. They are vital to predict landslide deformation monitoring. Currently, landslide deformation monitoring data on the whole process is rare. Most monitoring data is short-term before sliding event. The deformation monitoring data of some unexpected landslide is even more difficult to collect. Therefore, studies on the type and distribution of curve clusters are difficult due to the lack of data. Some of the landslide warning theories are derived from inferential and theoretical analysis and lack data support. With a physical modeling approach, a physic simulation framework is designed for variable angle. The displacement data automatic acquisition system is developed. During the testing for more than one year, the equipments and model materials are continuously adjusted and optimized. Eventually, seven groups of twelve displacement-time curves are collected. The landslide deformation and failure of displacement-time curve clusters under different loading conditions are obtained. They are scientific data for further theoretical research.
Displacement-time curves represent the status and relative stability of landslide deformation. They are vital to predict landslide deformation monitoring. Currently, landslide deformation monitoring data on the whole process is rare. Most monitoring data is short-term before sliding event. The deformation monitoring data of some unexpected landslide is even more difficult to collect. Therefore, studies on the type and distribution of curve clusters are difficult due to the lack of data. Some of the landslide warning theories are derived from inferential and theoretical analysis and lack data support. With a physical modeling approach, a physic simulation framework is designed for variable angle. The displacement data automatic acquisition system is developed. During the testing for more than one year, the equipments and model materials are continuously adjusted and optimized. Eventually, seven groups of twelve displacement-time curves are collected. The landslide deformation and failure of displacement-time curve clusters under different loading conditions are obtained. They are scientific data for further theoretical research.
2015, 23(3): 408-414.
On January 27, 2006, a rockfall happened at Yaoyanjiao of Houchang town in Weining county, Guizhou province. Yaoyanjiao high-steep slope has overlying strata covered by carbonate and underlain with soft rock. It also has nearly horizontal coal seams. Based on the analysis of disaster characteristic and process, the conceptual model of generation mechanism is established. There are several deep dissection dissolution cracks and horizontal caves caused by intense karst in high-steep slope. High-steep dyke is therefore formed in high-steep slope. The excessive mining of coal seam from the deep of slope body to slope surface has resulted in high stress concentration in the lower part of dyke and developed into failure. Quantitative analysis of generation mechanism and process is conducted by the employment of MIDAS/GTS software. Further analysis of critical safe distance of mining face from cliff face is done at different recovery ratios. The results can provide reference for analogous conditions of coal mining.
On January 27, 2006, a rockfall happened at Yaoyanjiao of Houchang town in Weining county, Guizhou province. Yaoyanjiao high-steep slope has overlying strata covered by carbonate and underlain with soft rock. It also has nearly horizontal coal seams. Based on the analysis of disaster characteristic and process, the conceptual model of generation mechanism is established. There are several deep dissection dissolution cracks and horizontal caves caused by intense karst in high-steep slope. High-steep dyke is therefore formed in high-steep slope. The excessive mining of coal seam from the deep of slope body to slope surface has resulted in high stress concentration in the lower part of dyke and developed into failure. Quantitative analysis of generation mechanism and process is conducted by the employment of MIDAS/GTS software. Further analysis of critical safe distance of mining face from cliff face is done at different recovery ratios. The results can provide reference for analogous conditions of coal mining.
PHYSICAL MODEL TESTS ON THE GROUTING SAND CONSOLIDATION ENGINEERING FOR SLOPE WITH GRANULAR MIXTURES
2015, 23(3): 415-419.
At present, there are limited studies on prevention and control measures of slope with granular mixtures. This paper recommends grouting sand to firm sand-sliding slope. Such sand slope has the characteristics of dynamic braking.This paper uses outdoor grouting physical simulation experiment. The grouted sand blocks have the shapes similar to tongue, ganoderma lucidum, cylindrical, long inverted cone and short inverted cone. The effective radiuses respectively are 46.3cm, 26cm, 21.4cm, 16.5cm, 40cm and 29.4cm. The screening tests are done on the stacking structure of granular mixtures influences on the grouting sand consolidation measures. The most main influence is the void ratio. The diffusion radius formula and grouting quantity formula are obtained with computer. The shear tests of consolidate bodies show that the shear strength is enhanced, which indicates the feasibility and rationality of grouting sand consolidation engineering. It is of great reference value for the grouting sand consolidation engineering.
At present, there are limited studies on prevention and control measures of slope with granular mixtures. This paper recommends grouting sand to firm sand-sliding slope. Such sand slope has the characteristics of dynamic braking.This paper uses outdoor grouting physical simulation experiment. The grouted sand blocks have the shapes similar to tongue, ganoderma lucidum, cylindrical, long inverted cone and short inverted cone. The effective radiuses respectively are 46.3cm, 26cm, 21.4cm, 16.5cm, 40cm and 29.4cm. The screening tests are done on the stacking structure of granular mixtures influences on the grouting sand consolidation measures. The most main influence is the void ratio. The diffusion radius formula and grouting quantity formula are obtained with computer. The shear tests of consolidate bodies show that the shear strength is enhanced, which indicates the feasibility and rationality of grouting sand consolidation engineering. It is of great reference value for the grouting sand consolidation engineering.
2015, 23(3): 420-428.
Designing of pile-anti-slide with anchor cable includes anchor cable tensile force and pile internal force. Pile internal force can be obtained by anchor cable tensile force. The cost of pile structure can be obtained by pile internal force. Then anchor cable tensile force affects the cost of pile-anchor cable structure. Therefore, anchor cable tensile force computing is especially important in the design of pile-anchor cable structure. This paper analyzes and studies the relationship between the cost of pile-anchor cable structure and anchor cable tensile force. It establishes anchor cable tensile force matching with the cost of pile-anchor cable structure calculation models from three aspects of relation curve model, polynomial fitting model and optimized deformation consistence condition model. It combinesm and Kmethods of pile internal force calculation and structural mechanics' principle of virtual work and diagram multiplication method. A calculation programs by Visual C++is complied to calculate the cost of pile-anchor cable structure with different anchor cable tensile force through different case studies. It presents the relation diagrams between the cost of pile-anchor cable structure and anchor cable tensile force. The results show that the cost of pile-anchor cable structure first decreases and then increases with the increase of anchor cable tensile force. Three kinds of model calculation results of anchor cable tensile force matching with the cost of pile-anchor cable structure are very close. Anchor cable tensile force calculated by any method can be considered as the final anchor cable tensile force design value. At this point, the plus and minus extremums of bending moment of pile are not equal. This also shows that anchor cable tensile force is not necessarily the optimal when the plus and minus extremums of bending moment of pile are equal. Although pile body status is ideal at the moment, the cost may be higher, so that economic benefit is poor.
Designing of pile-anti-slide with anchor cable includes anchor cable tensile force and pile internal force. Pile internal force can be obtained by anchor cable tensile force. The cost of pile structure can be obtained by pile internal force. Then anchor cable tensile force affects the cost of pile-anchor cable structure. Therefore, anchor cable tensile force computing is especially important in the design of pile-anchor cable structure. This paper analyzes and studies the relationship between the cost of pile-anchor cable structure and anchor cable tensile force. It establishes anchor cable tensile force matching with the cost of pile-anchor cable structure calculation models from three aspects of relation curve model, polynomial fitting model and optimized deformation consistence condition model. It combinesm and Kmethods of pile internal force calculation and structural mechanics' principle of virtual work and diagram multiplication method. A calculation programs by Visual C++is complied to calculate the cost of pile-anchor cable structure with different anchor cable tensile force through different case studies. It presents the relation diagrams between the cost of pile-anchor cable structure and anchor cable tensile force. The results show that the cost of pile-anchor cable structure first decreases and then increases with the increase of anchor cable tensile force. Three kinds of model calculation results of anchor cable tensile force matching with the cost of pile-anchor cable structure are very close. Anchor cable tensile force calculated by any method can be considered as the final anchor cable tensile force design value. At this point, the plus and minus extremums of bending moment of pile are not equal. This also shows that anchor cable tensile force is not necessarily the optimal when the plus and minus extremums of bending moment of pile are equal. Although pile body status is ideal at the moment, the cost may be higher, so that economic benefit is poor.
2015, 23(3): 429-437.
In the harder-hit earthquake areas such as Wenchuan, the constancy of unstable rock is considered as a key work of the disaster control because there are many kinds of geologic hazards caused by the earthquake. This paper is based on the reliability theory and uses the limit state characteristics of falling unstable rocks. It establishes the equation of constancy judging probability limit state. It also determines the mean value, variability and distribution shape of the unstable rock angle of rupture, the unstable rock angle of equivalent internal friction, weight per unit length, equivalent cohesion, height and other basic variables in the functions by means of field measurement and probability statistics. Based on these studies, the paper develops the calculation method of falling unstable rock stability reliability index. At the same time, it studies the parameter sensitivity of each basic variable. The result shows that the variables in descending order from high to low sensitivity are the unstable rock angle of rupture, the equivalent cohesion, the height, the weight per unit length and the angle of equivalent internal friction. The result offers a reference in judging the constancy of unstable rock and designing of a regulation scheme.
In the harder-hit earthquake areas such as Wenchuan, the constancy of unstable rock is considered as a key work of the disaster control because there are many kinds of geologic hazards caused by the earthquake. This paper is based on the reliability theory and uses the limit state characteristics of falling unstable rocks. It establishes the equation of constancy judging probability limit state. It also determines the mean value, variability and distribution shape of the unstable rock angle of rupture, the unstable rock angle of equivalent internal friction, weight per unit length, equivalent cohesion, height and other basic variables in the functions by means of field measurement and probability statistics. Based on these studies, the paper develops the calculation method of falling unstable rock stability reliability index. At the same time, it studies the parameter sensitivity of each basic variable. The result shows that the variables in descending order from high to low sensitivity are the unstable rock angle of rupture, the equivalent cohesion, the height, the weight per unit length and the angle of equivalent internal friction. The result offers a reference in judging the constancy of unstable rock and designing of a regulation scheme.
2015, 23(3): 438-447.
K117 landslide of Yong-Ning highway is a cutting slope with two excavation stages in argillaceous siltstone of monoclinic layer. The formation mechanism of this landslide is complex because it is the long run-out plane sliding as far as 35m and the sliding pit as long as 25m on slide bed when excavated. Based on the detailed investigation to its basic characteristics and development process, the landslide is simulated by joint finite element method in the process of its slide of three stages and landslide treatment. Firstly, the paper reappears the whole gestating process and stability evolving regulations of the landslide. It analyzes the plane sliding mechanism and the physical and mechanical characteristics of sliding surface. Next, it discusses the long run-out sliding mechanism induced by excavating relaxation and filling water within fissure. Lastly, it proposes six suggestions to predict and control this landslide. The results shows that, when the weak structure planes in monoclinic layer is exposed on free surface after excavating, it can activate unloading relaxation of the whole slope and cause the great imbalance thrust of landslide. Meanwhile, landslide is very sensitive because of rainfall infiltration in stretched cracks. Due to change of potential energy to kinetic energy, sliding surface can be cut off rapidly by the interaction of imbalance thrust and fissure water pressure. Then it can be converted into high-speed and long run-out sliding.
K117 landslide of Yong-Ning highway is a cutting slope with two excavation stages in argillaceous siltstone of monoclinic layer. The formation mechanism of this landslide is complex because it is the long run-out plane sliding as far as 35m and the sliding pit as long as 25m on slide bed when excavated. Based on the detailed investigation to its basic characteristics and development process, the landslide is simulated by joint finite element method in the process of its slide of three stages and landslide treatment. Firstly, the paper reappears the whole gestating process and stability evolving regulations of the landslide. It analyzes the plane sliding mechanism and the physical and mechanical characteristics of sliding surface. Next, it discusses the long run-out sliding mechanism induced by excavating relaxation and filling water within fissure. Lastly, it proposes six suggestions to predict and control this landslide. The results shows that, when the weak structure planes in monoclinic layer is exposed on free surface after excavating, it can activate unloading relaxation of the whole slope and cause the great imbalance thrust of landslide. Meanwhile, landslide is very sensitive because of rainfall infiltration in stretched cracks. Due to change of potential energy to kinetic energy, sliding surface can be cut off rapidly by the interaction of imbalance thrust and fissure water pressure. Then it can be converted into high-speed and long run-out sliding.
2015, 23(3): 448-453.
The vertical vibration of seismic wave attenuates faster than its horizontal vibration. Therefore only horizontal seismic force is considered in the mathematic model to analyze the failure of rock slope. The influence of length, buried depth and orientation of the structural plane to the failure of slope are analyzed respectively. It is found that when the buried depth and the length h/L are in a similar value, for a certain horizontal seismic acceleration a,the destruction of slope would be easier to occur with the increase of buried depth and length. While when the buried depth and length are keep in constant values, the failure of slope would become easier with the augment of horizontal seismic acceleration. Moreover, with the enlarge of inclination of structural plane, the tensile stress in rock masses would increase gradually. While the shear stress would boost at first and then decrease. This can be attributed to the reason that the failure of rock masses under earthquake would change from shear state to tensile state when the length and buried depth of structural plane are keep in constant. Moreover, according to the superstition principle of wave, the influence of length and buried depth to the dynamic response of slope under seismic loading is explored as well. The results can be referred to the assessment of seismic stability of slope.
The vertical vibration of seismic wave attenuates faster than its horizontal vibration. Therefore only horizontal seismic force is considered in the mathematic model to analyze the failure of rock slope. The influence of length, buried depth and orientation of the structural plane to the failure of slope are analyzed respectively. It is found that when the buried depth and the length h/L are in a similar value, for a certain horizontal seismic acceleration a,the destruction of slope would be easier to occur with the increase of buried depth and length. While when the buried depth and length are keep in constant values, the failure of slope would become easier with the augment of horizontal seismic acceleration. Moreover, with the enlarge of inclination of structural plane, the tensile stress in rock masses would increase gradually. While the shear stress would boost at first and then decrease. This can be attributed to the reason that the failure of rock masses under earthquake would change from shear state to tensile state when the length and buried depth of structural plane are keep in constant. Moreover, according to the superstition principle of wave, the influence of length and buried depth to the dynamic response of slope under seismic loading is explored as well. The results can be referred to the assessment of seismic stability of slope.
2015, 23(3): 454-461.
This paper is based on the in-depth analysis of the geometric meaning of reliability index and the basic idea of response surface method. It proposes the algorithm steps of reliability index on the basis of ANSYS and response surface method. The engineering geological conditions of Dalugou loess landslide in Wuqi County Shaanxi Province are analyzed. According to the landslide geological survey data and design information of landslide remediation engineering, the finite element model of anti-slide pile soil system is established on ANSYS software platform. The numerical simulation results of pile and soil system under own weight condition prove the validity of the finite element model. Moreover, the density of landslide, the cohesion c, the internal friction angle of slide surface, and the compression modulus Es of sliding bed are screened as random variables. The reliability calculation model of anti-slide pile is developed using ANSYS software and CCD responding surface method. The corresponding algorithm is developed. The sample calculation shows that, when the number of test point N equals to 25,the probability of failure of anti-slide pile structure Pf=0.35% and =2.70,which verifies the feasibility of establishing the reliability model and corresponding algorithm with ANSYS and CCD response surface method.
This paper is based on the in-depth analysis of the geometric meaning of reliability index and the basic idea of response surface method. It proposes the algorithm steps of reliability index on the basis of ANSYS and response surface method. The engineering geological conditions of Dalugou loess landslide in Wuqi County Shaanxi Province are analyzed. According to the landslide geological survey data and design information of landslide remediation engineering, the finite element model of anti-slide pile soil system is established on ANSYS software platform. The numerical simulation results of pile and soil system under own weight condition prove the validity of the finite element model. Moreover, the density of landslide, the cohesion c, the internal friction angle of slide surface, and the compression modulus Es of sliding bed are screened as random variables. The reliability calculation model of anti-slide pile is developed using ANSYS software and CCD responding surface method. The corresponding algorithm is developed. The sample calculation shows that, when the number of test point N equals to 25,the probability of failure of anti-slide pile structure Pf=0.35% and =2.70,which verifies the feasibility of establishing the reliability model and corresponding algorithm with ANSYS and CCD response surface method.
2015, 23(3): 462-468.
The debris flow deposition is the final product of debris flow. It contains a lot of information of transit process and development of debris flows. The research of deposition has reflected the debris flow hazard and activity intensity. Consequently, solid grains in the debris-flow deposits display a marked self-similarity in geometrical shape and scale-invariance in size according to fractal theory. The particle fractal dimension of debris flow deposition is calculated with fractal theory. By analyzing the relationship between fractal dimension and the length of the main channel, the ratio of loose material length along the channel to the total channel length, average gradient of the main channel, and maximum elevation difference, this paper finds the nonlinear response between fractal dimension and its influencing factors. According to fractal dimension data of debris flow in the Wudongde reservoir area, taking the aforementioned influencing factors as the input units, the support vector machine forecasting model is established. The fractal dimension of debris flow deposits is predicted. The maximum error is only 1.25%,which means the predicted values are consistent with the measured values. It is indicated that the support vector machine model has a great fitting and generalization ability. It is an effective method for prediction of debris flow deposits fractal dimension, which can also be used to deduce the distribution law of particle for debris flows without sample sieve analysis. Besides it provides a new idea for researching the following subjects: formation mechanism, type, hazard of debris flow and formation characteristic, physical and mechanical properties of debris flow deposits.
The debris flow deposition is the final product of debris flow. It contains a lot of information of transit process and development of debris flows. The research of deposition has reflected the debris flow hazard and activity intensity. Consequently, solid grains in the debris-flow deposits display a marked self-similarity in geometrical shape and scale-invariance in size according to fractal theory. The particle fractal dimension of debris flow deposition is calculated with fractal theory. By analyzing the relationship between fractal dimension and the length of the main channel, the ratio of loose material length along the channel to the total channel length, average gradient of the main channel, and maximum elevation difference, this paper finds the nonlinear response between fractal dimension and its influencing factors. According to fractal dimension data of debris flow in the Wudongde reservoir area, taking the aforementioned influencing factors as the input units, the support vector machine forecasting model is established. The fractal dimension of debris flow deposits is predicted. The maximum error is only 1.25%,which means the predicted values are consistent with the measured values. It is indicated that the support vector machine model has a great fitting and generalization ability. It is an effective method for prediction of debris flow deposits fractal dimension, which can also be used to deduce the distribution law of particle for debris flows without sample sieve analysis. Besides it provides a new idea for researching the following subjects: formation mechanism, type, hazard of debris flow and formation characteristic, physical and mechanical properties of debris flow deposits.
2015, 23(3): 469-476.
Severe damage of alpine mountain rock slopes due to frost-thaw weathering affects road construction and safe operation. This paper is to reveal the failure mechanism of rocks under freeze-thaw conditions. It is based on the site catalog of alpine mountain rock slope, and combined with laboratory experiments and numerical simulation. A comprehensive evaluation of freeze-thaw damage mechanism of rock is presented. Indoor experiments have showed that rock strength is weakened after freezing and thawing. It is controlled by the rock texture and structure, the degree of cementation and the initial fractures. The freeze-thaw tests reveal that development of rock fractures plays a decisive role in the nature of frost heave. The freeze-thaw damage rate along the fractures is far greater than the intact rocks. The process of fissure water frozen into ice forms the split effect. The expansion force can be reach to 33MPa or greater. Numerical analysis reveals that the slope temperature field is affected by low and large temperature difference. Fractured zone is the most obvious area that is affected by freezing and thawing. It is the channel of slope freeze-thaw weathering. The congelifraction formed by fracture water frost heave is the main model of slope freeze-thaw weathering damage.
Severe damage of alpine mountain rock slopes due to frost-thaw weathering affects road construction and safe operation. This paper is to reveal the failure mechanism of rocks under freeze-thaw conditions. It is based on the site catalog of alpine mountain rock slope, and combined with laboratory experiments and numerical simulation. A comprehensive evaluation of freeze-thaw damage mechanism of rock is presented. Indoor experiments have showed that rock strength is weakened after freezing and thawing. It is controlled by the rock texture and structure, the degree of cementation and the initial fractures. The freeze-thaw tests reveal that development of rock fractures plays a decisive role in the nature of frost heave. The freeze-thaw damage rate along the fractures is far greater than the intact rocks. The process of fissure water frozen into ice forms the split effect. The expansion force can be reach to 33MPa or greater. Numerical analysis reveals that the slope temperature field is affected by low and large temperature difference. Fractured zone is the most obvious area that is affected by freezing and thawing. It is the channel of slope freeze-thaw weathering. The congelifraction formed by fracture water frost heave is the main model of slope freeze-thaw weathering damage.
2015, 23(3): 477-484.
Rock crack propagation cannot be simulated with conventional finite element method because it is a classic discontinuity problem. Extended finite element method(XFEM)can implement the mutual independence of computational grid and discontinuity. So there is no need to re-mesh the grid model for moving discontinuity simulation. This paper introduces the basic principles of XFEM and universal criterion for rock fracture mechanics. It utilizes XFEM to simulate I mode and II mode fracture in three-point bending test as well as the double-crack shear fracture test. All the obtained results indicate that using XFEM to simulate rock fracture cannot be restrained by mesh generation and the cracks propagate randomly according to the actual stress distribution. The whole process of micro crack generation and evolution until the final total destruction of rock can be directly observed, which have great agreement with laboratory test results. This method has demonstrated its ability to investigate rock fracture mechanics and to simulate rock macroscopic and microscopic fracture process. It provides a convenient way for complex issues solution.
Rock crack propagation cannot be simulated with conventional finite element method because it is a classic discontinuity problem. Extended finite element method(XFEM)can implement the mutual independence of computational grid and discontinuity. So there is no need to re-mesh the grid model for moving discontinuity simulation. This paper introduces the basic principles of XFEM and universal criterion for rock fracture mechanics. It utilizes XFEM to simulate I mode and II mode fracture in three-point bending test as well as the double-crack shear fracture test. All the obtained results indicate that using XFEM to simulate rock fracture cannot be restrained by mesh generation and the cracks propagate randomly according to the actual stress distribution. The whole process of micro crack generation and evolution until the final total destruction of rock can be directly observed, which have great agreement with laboratory test results. This method has demonstrated its ability to investigate rock fracture mechanics and to simulate rock macroscopic and microscopic fracture process. It provides a convenient way for complex issues solution.
2015, 23(3): 485-490.
According to three fundamental assumptions of wedge rockmass(wedge) failure, a physical model of wedge in underground cavities is established and a limit equilibrium method for wedge stability analysis is proposed. The method can obtain a stability coefficient calculation expression to judge stability state pursuant to the geometrical analysis. It further discusses wedge stability dynamic response under blasting construction load. Case analysis indicates that wedge in gravity is in a stable state, and the wedge stability increases when the wedge is exerted by beginning blasting load. Engineering blasting load is much greater than the weight of wedge. Blasting load can play a leading role in the wedge stability. When blasting stress waves reflect the wedge, its stability decreases markedly. Single sliding failure of wedge occurs along surface ①.
According to three fundamental assumptions of wedge rockmass(wedge) failure, a physical model of wedge in underground cavities is established and a limit equilibrium method for wedge stability analysis is proposed. The method can obtain a stability coefficient calculation expression to judge stability state pursuant to the geometrical analysis. It further discusses wedge stability dynamic response under blasting construction load. Case analysis indicates that wedge in gravity is in a stable state, and the wedge stability increases when the wedge is exerted by beginning blasting load. Engineering blasting load is much greater than the weight of wedge. Blasting load can play a leading role in the wedge stability. When blasting stress waves reflect the wedge, its stability decreases markedly. Single sliding failure of wedge occurs along surface ①.
2015, 23(3): 491-497.
The slope surface deformation and displacement are related to the precipitation. The root cause is volumetric strain caused by suction decreasing in unsaturated soils. By simply increasing the suction stress path, under net confining pressure of 100kPa or 200kPa, the test of volumetric strain due to suction is done on undisturbed landslide samples and its remolded sample. The results show: (1)The volumetric strain of the specimen monotonically increases with suction increasing, which obeys logarithm function relation; (2)Bulk modulus during net confining pressure from 100kPa to 200kPa, monotonically increases with suction increasing, which obeys the power function relationship; (3)Coefficient of volume change associated with the suction monotonically decreases with suction increasing, which obeys the power function relationship. When the suction is greater than 200kPa, with the suction increases, the volume change of coefficients is close to a constant of about 0.0059. Based on these results, the pattern and mechanics of volumetric strain caused by a simple suction change are discussed in this paper.
The slope surface deformation and displacement are related to the precipitation. The root cause is volumetric strain caused by suction decreasing in unsaturated soils. By simply increasing the suction stress path, under net confining pressure of 100kPa or 200kPa, the test of volumetric strain due to suction is done on undisturbed landslide samples and its remolded sample. The results show: (1)The volumetric strain of the specimen monotonically increases with suction increasing, which obeys logarithm function relation; (2)Bulk modulus during net confining pressure from 100kPa to 200kPa, monotonically increases with suction increasing, which obeys the power function relationship; (3)Coefficient of volume change associated with the suction monotonically decreases with suction increasing, which obeys the power function relationship. When the suction is greater than 200kPa, with the suction increases, the volume change of coefficients is close to a constant of about 0.0059. Based on these results, the pattern and mechanics of volumetric strain caused by a simple suction change are discussed in this paper.
2015, 23(3): 498-504.
The design conception of composite liners is consisted of a geomembrane(GM),geosynthetic clay liners(GCls) and compacted gravel soils in landfills. This conception is presented on the basis of the climate characteristics, gravel soils material rich in nature, and GCls that have been exported all over the world for various applications. The artificially graded gravel soils are taken from natural sediment zone for flood alluvial at Yinchuan suburb in Ningxia. The gravel soil is figured out to meet the requirement of permeability coefficient through the compaction and penetration experiment. The frost-heaving ratio and hydraulic conductivity of gravel soil samples are tested under freeze-thaw cycling in this paper. The test results indicate that the frost-heaving ratio increases as the number of freeze-thaw increases. As the number of freeze-thaw increases, the permeability coefficient also increases. The permeability coefficient is increased by one to two orders of magnitude after 12 cycles of freezing-thawing. At the beginning of freeze-thaw cycle, it has an influence on the soil samples. The influence tends to be relatively stable state as the number of freeze-thaw cycles increases. The sensitivity of gravel soils under freeze-thaw cycling is less than that of the silt clay. It is acceptable to undertake the landfill composite liners which will be comprised of GCls/GM and compacted gravel soils together.
The design conception of composite liners is consisted of a geomembrane(GM),geosynthetic clay liners(GCls) and compacted gravel soils in landfills. This conception is presented on the basis of the climate characteristics, gravel soils material rich in nature, and GCls that have been exported all over the world for various applications. The artificially graded gravel soils are taken from natural sediment zone for flood alluvial at Yinchuan suburb in Ningxia. The gravel soil is figured out to meet the requirement of permeability coefficient through the compaction and penetration experiment. The frost-heaving ratio and hydraulic conductivity of gravel soil samples are tested under freeze-thaw cycling in this paper. The test results indicate that the frost-heaving ratio increases as the number of freeze-thaw increases. As the number of freeze-thaw increases, the permeability coefficient also increases. The permeability coefficient is increased by one to two orders of magnitude after 12 cycles of freezing-thawing. At the beginning of freeze-thaw cycle, it has an influence on the soil samples. The influence tends to be relatively stable state as the number of freeze-thaw cycles increases. The sensitivity of gravel soils under freeze-thaw cycling is less than that of the silt clay. It is acceptable to undertake the landfill composite liners which will be comprised of GCls/GM and compacted gravel soils together.
2015, 23(3): 505-510.
Composite foundation aims at controlling settlement. Settlement calculation plays an important role in soft soil foundation design and construction stages. Based on the typical unit cell model of piles and soil, the relationship between composite foundation compression coefficient and elasticity modulus has been established. The factors such as time and consolidation have been taken into consideration. The settlements have been evaluated to verify the formula proposed in this paper. The formula is applied to the settlement deformation observation data of the soft ground distributed along the Suining-Ziyang expressway in Sichuan province. The formula's feasibility is further verified. The research shows that the calculation data are 10-20 times higher than the observed data. During the filling stage, the result calculated by the proposed method is in accordance with the observed results of the project. Based on these, the paper discusses primarily for the influential factors of the settlement such as pile diameter and the pile spacing. The best ratio of pile diameter and pile spacing is from 2 to 4.
Composite foundation aims at controlling settlement. Settlement calculation plays an important role in soft soil foundation design and construction stages. Based on the typical unit cell model of piles and soil, the relationship between composite foundation compression coefficient and elasticity modulus has been established. The factors such as time and consolidation have been taken into consideration. The settlements have been evaluated to verify the formula proposed in this paper. The formula is applied to the settlement deformation observation data of the soft ground distributed along the Suining-Ziyang expressway in Sichuan province. The formula's feasibility is further verified. The research shows that the calculation data are 10-20 times higher than the observed data. During the filling stage, the result calculated by the proposed method is in accordance with the observed results of the project. Based on these, the paper discusses primarily for the influential factors of the settlement such as pile diameter and the pile spacing. The best ratio of pile diameter and pile spacing is from 2 to 4.
2015, 23(3): 511-520.
Based on the mesoscopic heterogeneity of rock, the RFPA2D-Flow software is used to explore the law of fracking. In this model, material is discretized into a large number of elements with the same size and different mechanical and permeable parameters in order to represent heterogeneity of rock. A coupling analysis of seepage and damage under hydraulic fracturing on rock is performed to simulate the fracture process of rock. Through the numerical results of single and double hole model, we draw the conclusions as follows:(1)The rock heterogeneity influences the pattern of fracture, results in the branching of hydraulic fracture. With the increase of the homogeneity, form of hydraulic fracture gets much smoother. The fractures in the single wellbore model are more symmetrical on both sides of wellbore. The connectivity between the double holes gets worse.(2)Heterogeneity of rock has a significant influence on the initiation and breakdown pressure. Both fracture initiation and breakdown pressure values increase with the increasing homogeneity. When the rock is homogeneous, both are almost equal.(3) At the same boundary conditions, the stress distribution curve of homogenous model is smooth and continuous, however, the curve display fluctuation in heterogeneous model. The fluctuation gets obvious with the increasing heterogeneity.(4)Pore pressure increment zone exists between the two holes in the double hole model, anattract effect occurs between the two holes, the critical pressure is influenced by the orientation of the two holes. The above results are of some significance to hydraulic fracturing tests and engineering practice.
Based on the mesoscopic heterogeneity of rock, the RFPA2D-Flow software is used to explore the law of fracking. In this model, material is discretized into a large number of elements with the same size and different mechanical and permeable parameters in order to represent heterogeneity of rock. A coupling analysis of seepage and damage under hydraulic fracturing on rock is performed to simulate the fracture process of rock. Through the numerical results of single and double hole model, we draw the conclusions as follows:(1)The rock heterogeneity influences the pattern of fracture, results in the branching of hydraulic fracture. With the increase of the homogeneity, form of hydraulic fracture gets much smoother. The fractures in the single wellbore model are more symmetrical on both sides of wellbore. The connectivity between the double holes gets worse.(2)Heterogeneity of rock has a significant influence on the initiation and breakdown pressure. Both fracture initiation and breakdown pressure values increase with the increasing homogeneity. When the rock is homogeneous, both are almost equal.(3) At the same boundary conditions, the stress distribution curve of homogenous model is smooth and continuous, however, the curve display fluctuation in heterogeneous model. The fluctuation gets obvious with the increasing heterogeneity.(4)Pore pressure increment zone exists between the two holes in the double hole model, anattract effect occurs between the two holes, the critical pressure is influenced by the orientation of the two holes. The above results are of some significance to hydraulic fracturing tests and engineering practice.
2015, 23(3): 521-525.
Settlement of muddy clay includes immediate settlement and primary-secondary consolidation settlement on the basis of Terzaghi's consolidation theory. Using the settlement law of muddy clay, this paper puts forward a modified settlement-velocity ratio method to calculate muddy clay settlement. The method can predict the settlement of muddy clay by means of getting consolidation coefficient. The consolidation coefficient can be reached by analyzing the settlement velocity with least square method. The example shows that predicted settlements and measured values are anastomotic, which means that the method can provide references for similar projects.
Settlement of muddy clay includes immediate settlement and primary-secondary consolidation settlement on the basis of Terzaghi's consolidation theory. Using the settlement law of muddy clay, this paper puts forward a modified settlement-velocity ratio method to calculate muddy clay settlement. The method can predict the settlement of muddy clay by means of getting consolidation coefficient. The consolidation coefficient can be reached by analyzing the settlement velocity with least square method. The example shows that predicted settlements and measured values are anastomotic, which means that the method can provide references for similar projects.
2015, 23(3): 526-532.
The high permeability of loose formation, the large consumption plasma of anti-seepage grouting and irregular diffusion have a great deal of uncertainty. So, it is very difficult to accurately grasp the structural traits of the formed impervious curtain, which contains impervious curtain thickness, mechanical properties, anti-seepage effect and other elements. Existing methods and techniques on the assessment of impervious quality mainly include that water pressure test, standard grout depth, coring, physical probe and other methods to access relevant information, which would impose a direct effect. In this study, injection test, hole skew measurement, coring test, whole section excavation and other methods are applied in field, the characters of anti-seepage structure include curtain effective thickness and its sphere of influence, curtain strength properties and permeability characteristic. They are revealed by experimental tests in various operating conditions. Under the condition of 1.5m pitch-row and 0.8m double-row distance, the experimental results show that it is very simple and efficient to adopt the technique of slurry sealing means and pulsating grouting ways to control the grouting process and the utilization of controllable clay grout material with appropriate grouting control parameters. Meanwhile, the periphery hole compaction zone, effective body and cemented stones curtain body are formed uniform and effective. The seepage coefficient reaches 5 lu below. The 28days stone strength after grouting reaches over 3.0MPa. In the effect contrast to pulp and stable slurry paste perfusion, it is found that if grout with stable slurry, it will be mainly with splitting permeability and the diffusion distance will be further than pulp. For higher seepage reinforcement requirements engineering, it will be the best to do the paste perfusion first, and then the stable slurry irrigation. Pulp veins mainly concentrate in the 1m radius around the grouting pipe, accounting for more than 60% of the total grouting volume. It can form an effective impervious body. The soil within 1.0m generates a significant displacement and outside 1.5m generates a small displacement. Grouting technology and parameters can be directly applied to the similar formations of layer. It is necessary to develop a physical model for studying in a large sample for the grouting construction characters of different types of formations in different grouting materials, grouting process and grouting parameters. The main conclusions include the following three parts. The first one is to propose grouting structure traits conceptual model for the characteristics of the soft ground.The process of closing slurry, pulsating grouting, and controllability clay grout material are suitable and clear for construction control perfusion parameters. Excavation pulp veins show a clear outcome. Compaction of cement and overlapping curtain grouting shows effectively the process of grouting and controlling parameters. All can be directly applied to similar projects. The second one is to improve the proposed measures to improve the structure of traits: analyze grouting formation effectively, select grouting process in line with the characteristics of the formation, research and experimental hole data sufficiently to determine the formation groutability, choose the appropriate grouting material, hole distance, grout volume and grouting pressure. The third way is to take the excavation which can be directly observed plasma pulse shaping and stone body. But the cost is pretty high. To understand the grouting structure traits of the different types of formations in different grouting materials, grouting process, and different grouting parameters, developing physical model and obtaining valuable results through large sample laboratory tests are needed next.
The high permeability of loose formation, the large consumption plasma of anti-seepage grouting and irregular diffusion have a great deal of uncertainty. So, it is very difficult to accurately grasp the structural traits of the formed impervious curtain, which contains impervious curtain thickness, mechanical properties, anti-seepage effect and other elements. Existing methods and techniques on the assessment of impervious quality mainly include that water pressure test, standard grout depth, coring, physical probe and other methods to access relevant information, which would impose a direct effect. In this study, injection test, hole skew measurement, coring test, whole section excavation and other methods are applied in field, the characters of anti-seepage structure include curtain effective thickness and its sphere of influence, curtain strength properties and permeability characteristic. They are revealed by experimental tests in various operating conditions. Under the condition of 1.5m pitch-row and 0.8m double-row distance, the experimental results show that it is very simple and efficient to adopt the technique of slurry sealing means and pulsating grouting ways to control the grouting process and the utilization of controllable clay grout material with appropriate grouting control parameters. Meanwhile, the periphery hole compaction zone, effective body and cemented stones curtain body are formed uniform and effective. The seepage coefficient reaches 5 lu below. The 28days stone strength after grouting reaches over 3.0MPa. In the effect contrast to pulp and stable slurry paste perfusion, it is found that if grout with stable slurry, it will be mainly with splitting permeability and the diffusion distance will be further than pulp. For higher seepage reinforcement requirements engineering, it will be the best to do the paste perfusion first, and then the stable slurry irrigation. Pulp veins mainly concentrate in the 1m radius around the grouting pipe, accounting for more than 60% of the total grouting volume. It can form an effective impervious body. The soil within 1.0m generates a significant displacement and outside 1.5m generates a small displacement. Grouting technology and parameters can be directly applied to the similar formations of layer. It is necessary to develop a physical model for studying in a large sample for the grouting construction characters of different types of formations in different grouting materials, grouting process and grouting parameters. The main conclusions include the following three parts. The first one is to propose grouting structure traits conceptual model for the characteristics of the soft ground.The process of closing slurry, pulsating grouting, and controllability clay grout material are suitable and clear for construction control perfusion parameters. Excavation pulp veins show a clear outcome. Compaction of cement and overlapping curtain grouting shows effectively the process of grouting and controlling parameters. All can be directly applied to similar projects. The second one is to improve the proposed measures to improve the structure of traits: analyze grouting formation effectively, select grouting process in line with the characteristics of the formation, research and experimental hole data sufficiently to determine the formation groutability, choose the appropriate grouting material, hole distance, grout volume and grouting pressure. The third way is to take the excavation which can be directly observed plasma pulse shaping and stone body. But the cost is pretty high. To understand the grouting structure traits of the different types of formations in different grouting materials, grouting process, and different grouting parameters, developing physical model and obtaining valuable results through large sample laboratory tests are needed next.
2015, 23(3): 533-538.
The mountain resort and its outlying temples, Chengde, located 250km northeast to Beijing, were built between 1703 and 1792. They are the Qing dynasty's royal gardens and temples. In 1994,it was listed as a World Heritage Site by UNESCO. Sandstone blocks were extensively used for the buildings. Many stone relics have been suffered from various weathering diseases including crack, scaling, disintegration, and biological invasion due to long-term weathering. In the paper, properties of mineralogy, physical and mechanical of weathered and unweathered sandstone samples are analyzed using petrographical and petrophysical methods. On this basis, deterioration mechanism is analyzed. The main causes of the sandstone weathering(main including scaling and disintegration) are dissolution calcareous cement, drying-wetting cycle and salt crystallization. The results can facilitate the choice of the most suitable conservation method.
The mountain resort and its outlying temples, Chengde, located 250km northeast to Beijing, were built between 1703 and 1792. They are the Qing dynasty's royal gardens and temples. In 1994,it was listed as a World Heritage Site by UNESCO. Sandstone blocks were extensively used for the buildings. Many stone relics have been suffered from various weathering diseases including crack, scaling, disintegration, and biological invasion due to long-term weathering. In the paper, properties of mineralogy, physical and mechanical of weathered and unweathered sandstone samples are analyzed using petrographical and petrophysical methods. On this basis, deterioration mechanism is analyzed. The main causes of the sandstone weathering(main including scaling and disintegration) are dissolution calcareous cement, drying-wetting cycle and salt crystallization. The results can facilitate the choice of the most suitable conservation method.
2015, 23(3): 539-547.
The resistivity of soil is an important parameter to describe its electrical conductivity. Through in-situ testing of resistivity and laboratory tests, the characteristics of resistivity of clayey soil and the relationship between resistivity and geotechnical parameters were studied.22 logs of resistivity were measured in the first-stage terrace of Wuhan district. All these logs were placed along the traces of the No.7metro of Wuhan. Routine soil test, non-confined compression test, quick shear test and triaxial shear test were done by using samples taken from these logs. It was found that, firstly, the resistivity of clayey soil increased with the increase of water content and void ratio; secondly, the resistivity decreased with the increase of non-confined compressive strength; thirdly; according to the result of triaxial shear test, the resistivity decreased with the increase of cohesion and angle of internal friction. Through linear and polynomial fit, the mathematic expression between resistivity and geotechnical parameters of clayey soil were offered. The correlation between the resistivity and those indexes are significant.
The resistivity of soil is an important parameter to describe its electrical conductivity. Through in-situ testing of resistivity and laboratory tests, the characteristics of resistivity of clayey soil and the relationship between resistivity and geotechnical parameters were studied.22 logs of resistivity were measured in the first-stage terrace of Wuhan district. All these logs were placed along the traces of the No.7metro of Wuhan. Routine soil test, non-confined compression test, quick shear test and triaxial shear test were done by using samples taken from these logs. It was found that, firstly, the resistivity of clayey soil increased with the increase of water content and void ratio; secondly, the resistivity decreased with the increase of non-confined compressive strength; thirdly; according to the result of triaxial shear test, the resistivity decreased with the increase of cohesion and angle of internal friction. Through linear and polynomial fit, the mathematic expression between resistivity and geotechnical parameters of clayey soil were offered. The correlation between the resistivity and those indexes are significant.
2015, 23(3): 548-553.
The shear strength of Taihu lake and Baimahu lake dredged slurries are tested with miniature shear vane apparatus at different stewing times after remolded. The thixotropy of two kinds of dredged slurries is studied. Test result shows that a sharp thixotropic strength increase at the first time after remolded is recorded. Then the thixotropic strength still increases, but at a slower rate. The increase of the thixotropic strength at 448d tends to be stable. The thixotropic strength of Taihu lake dredged slurries is higher than that of Baimahu lake at the liquid limit. The variation trend of thixotropic strength ratio is similar with the thixotropic strength. The thixotropy of dredged slurries increases with decreasing water content. The thixotropic strength ratio of the two kinds of dredged slurries at the liquid limit is close to that of the London and Detroit dredged slurries. It is less than that of Beauharnois and Shellhave dredged slurries. It is greater than that of Horten dredged slurries. The thixotropic strength ratio of the others besides the Beauharnois dredged slurries keeps stable at 448d. The two kinds of dredged slurries are low sensitivity clays according to the definition of the clays sensitivity.
The shear strength of Taihu lake and Baimahu lake dredged slurries are tested with miniature shear vane apparatus at different stewing times after remolded. The thixotropy of two kinds of dredged slurries is studied. Test result shows that a sharp thixotropic strength increase at the first time after remolded is recorded. Then the thixotropic strength still increases, but at a slower rate. The increase of the thixotropic strength at 448d tends to be stable. The thixotropic strength of Taihu lake dredged slurries is higher than that of Baimahu lake at the liquid limit. The variation trend of thixotropic strength ratio is similar with the thixotropic strength. The thixotropy of dredged slurries increases with decreasing water content. The thixotropic strength ratio of the two kinds of dredged slurries at the liquid limit is close to that of the London and Detroit dredged slurries. It is less than that of Beauharnois and Shellhave dredged slurries. It is greater than that of Horten dredged slurries. The thixotropic strength ratio of the others besides the Beauharnois dredged slurries keeps stable at 448d. The two kinds of dredged slurries are low sensitivity clays according to the definition of the clays sensitivity.
2015, 23(3): 554-563.
The dam area of Pingzhai reservoir is dominated with carbonate rocks. Karst develops seriously. A large filled karst cave is discovered in bottom grouting gallery on the left bank of dam site. It is the largest in scale and it mostly affects the seepage of reservoir. The design and construction about the cave are the most difficult one among all of the caves discovered during the excavation of underground engineering. This paper is based on the engineering geological exploration carried on before design stage and the study about regional landforms, geological structure, stratum lithology and river system of surface and underground water. It further combines the karst hydro geological phenomenon and cave fillings discovered during the construction of curtain grouting engineering. This paper examines the four aspects including soluble rock, groundwater sources and transport and erosion of underground river, collapse of cave roof. It studies the formation mechanism of karst development, carries on the analysis. It finds that there are the NW longitudinal tension fractures and horizontal tensile cracks on Jichang anticline and interlayer gliding, and the fault structural fracture zone. They provide the original space and channel for karst system of Wuli Cave-Jichang depression-Shangba depression runoff to Shanchahe. They provide the formation of karst caves of groundwater, the long-term corrosion caused fissure channel to wide crack then to karst pipe, and forms the inverted siphon circulation of karst water at 0+220m0+238m of mileage in the bottom grouting gallery on the left bank. Strong erosion and roof collapse are also immensely helpful in cave formation. Due to deep runoff conditions are changed and channel for karst gradually is filled, the large filled karst cave is developed finally.
The dam area of Pingzhai reservoir is dominated with carbonate rocks. Karst develops seriously. A large filled karst cave is discovered in bottom grouting gallery on the left bank of dam site. It is the largest in scale and it mostly affects the seepage of reservoir. The design and construction about the cave are the most difficult one among all of the caves discovered during the excavation of underground engineering. This paper is based on the engineering geological exploration carried on before design stage and the study about regional landforms, geological structure, stratum lithology and river system of surface and underground water. It further combines the karst hydro geological phenomenon and cave fillings discovered during the construction of curtain grouting engineering. This paper examines the four aspects including soluble rock, groundwater sources and transport and erosion of underground river, collapse of cave roof. It studies the formation mechanism of karst development, carries on the analysis. It finds that there are the NW longitudinal tension fractures and horizontal tensile cracks on Jichang anticline and interlayer gliding, and the fault structural fracture zone. They provide the original space and channel for karst system of Wuli Cave-Jichang depression-Shangba depression runoff to Shanchahe. They provide the formation of karst caves of groundwater, the long-term corrosion caused fissure channel to wide crack then to karst pipe, and forms the inverted siphon circulation of karst water at 0+220m0+238m of mileage in the bottom grouting gallery on the left bank. Strong erosion and roof collapse are also immensely helpful in cave formation. Due to deep runoff conditions are changed and channel for karst gradually is filled, the large filled karst cave is developed finally.
2015, 23(3): 564-573.
Extensive research has been conducted for the seismic response character of the underground engineering. Meanwhile less effect has been put on the seismic input mechanism in the dynamic analysis. To cover this regretful circumstance, this paper makes some discussions on this issue. A rational selection process is firstly proposed for various types of ground motion. The types include original record, modified record, and artificial simulated waves. Design ground motion reference plane(point) and artificial boundary input ground motion determining approach are then studied. A seismic input procedure is formed specifically for underground cavern complex. The seismic input mechanism is methodical and interpreted by integrating the ground motion selection process and seismic input procedure. Ultimately, demonstrations are conducted for the Baihetan underground cavern complex with proposed approaches.
Extensive research has been conducted for the seismic response character of the underground engineering. Meanwhile less effect has been put on the seismic input mechanism in the dynamic analysis. To cover this regretful circumstance, this paper makes some discussions on this issue. A rational selection process is firstly proposed for various types of ground motion. The types include original record, modified record, and artificial simulated waves. Design ground motion reference plane(point) and artificial boundary input ground motion determining approach are then studied. A seismic input procedure is formed specifically for underground cavern complex. The seismic input mechanism is methodical and interpreted by integrating the ground motion selection process and seismic input procedure. Ultimately, demonstrations are conducted for the Baihetan underground cavern complex with proposed approaches.
2015, 23(3): 574-579.
Water head drawdown during dewatering in confined aquifers closely relates to multi-well effect. An ultra-large pit is studied in this paper. The pit features 40-meter-thick aquifers, is high permeability at middle and down side, and uses partial pumping wells. Based on the summarization of hydrogeological conditions, a three dimensional unsteady-flow numerical model of underground water is built and used to simulate the seepage field under different scenarios. They include even and uneven distribution of wells, excavation and dewatering by blocks, various well structures and deployment of injection wells. The research shows (1)Ultra-large pit in highly permeable aquifers has obvious multi-well effect; (2)Dense at Corner and Sparse at Center well deployment unifies water head drawdown and avoids insufficient or excessive dewatering; (3)Excavation and dewatering by blocks suppresses drawdown outside the pit; (4)Well structure with short screen pipe reduces total water yield and suppresses outside drawdown; (5)Aquifers of high permeability are highly rechargeable and recharging has fairly obvious effect on suppressing outside drawdown. Simulation results are consistent with in-situ monitoring. The research result can serve as a reference to similar underground water level control project.
Water head drawdown during dewatering in confined aquifers closely relates to multi-well effect. An ultra-large pit is studied in this paper. The pit features 40-meter-thick aquifers, is high permeability at middle and down side, and uses partial pumping wells. Based on the summarization of hydrogeological conditions, a three dimensional unsteady-flow numerical model of underground water is built and used to simulate the seepage field under different scenarios. They include even and uneven distribution of wells, excavation and dewatering by blocks, various well structures and deployment of injection wells. The research shows (1)Ultra-large pit in highly permeable aquifers has obvious multi-well effect; (2)Dense at Corner and Sparse at Center well deployment unifies water head drawdown and avoids insufficient or excessive dewatering; (3)Excavation and dewatering by blocks suppresses drawdown outside the pit; (4)Well structure with short screen pipe reduces total water yield and suppresses outside drawdown; (5)Aquifers of high permeability are highly rechargeable and recharging has fairly obvious effect on suppressing outside drawdown. Simulation results are consistent with in-situ monitoring. The research result can serve as a reference to similar underground water level control project.
2015, 23(3): 580-588.
Geo-environmental problems of mining cities have been increasing in China. It is necessary to assess mine geo-environment impact(MGEI)in these mining cities for instructing the mine development and protecting environment. RS data is adopted to assess MGEI in the Daye mining area in southeastern Hubei Province. A MGEI index system is established by considering geo-environment background, geo-environment problems and mining activities. The fussy comprehensive assessment method is employed to assess the geo-hazard susceptibility before mining and the MGEI after mining respectively. The result indicates that:(1)Under the natural state, the high, medium, relatively low and low easy-happening areas of geological hazard take up 3.29%, 12.55%, 24.53% and 59.62%,respectively.(2)Under the mining state, the severely, less severely, relatively slightly and slightly impacted areas of mine geo-environment take up 13.63%, 22.96%, 33.95% and 29.46%,respectively. The assessment result can be applied in mine planning and comprehensive geo-environment reclamation.
Geo-environmental problems of mining cities have been increasing in China. It is necessary to assess mine geo-environment impact(MGEI)in these mining cities for instructing the mine development and protecting environment. RS data is adopted to assess MGEI in the Daye mining area in southeastern Hubei Province. A MGEI index system is established by considering geo-environment background, geo-environment problems and mining activities. The fussy comprehensive assessment method is employed to assess the geo-hazard susceptibility before mining and the MGEI after mining respectively. The result indicates that:(1)Under the natural state, the high, medium, relatively low and low easy-happening areas of geological hazard take up 3.29%, 12.55%, 24.53% and 59.62%,respectively.(2)Under the mining state, the severely, less severely, relatively slightly and slightly impacted areas of mine geo-environment take up 13.63%, 22.96%, 33.95% and 29.46%,respectively. The assessment result can be applied in mine planning and comprehensive geo-environment reclamation.
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