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Editor Work2013 Vol. 21, No. 6
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2013, 21(6): 819-827.
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With global warming and more extreme climate hazards, China is facing more environment impact, operational risk management, and many other security issues and challenges. With the fast development of hydropower, nuclear power and other major projects, these issues and challenges need to be thought deeply and solved by joint research. In order to achieve the sustainable development and harmonious regulation of the Project-Economy-Society-Environment-Energy and Resources as one complex giant system, scientists need to demonstrate them repeatedly, from the perspective of national even global, all-round, multi-level, multi-disciplinary, and not confined to a particular sector or industry. On the basis of the re-thinking analysis on large-scale engineering accidents and their related hazards, the authors think it is necessary to conclude the reasons and lessons from the failures, and establish a cross disciplinary Eco-Geological Engineering to boost the theoretical research and engineering applications of the complex giant system. Therefore, researchers can achieve the long term goal of project construction, ecological and environmental protection and sustainable economic development, instead of considering merely the site security of the project and the stability of rock mass.
With global warming and more extreme climate hazards, China is facing more environment impact, operational risk management, and many other security issues and challenges. With the fast development of hydropower, nuclear power and other major projects, these issues and challenges need to be thought deeply and solved by joint research. In order to achieve the sustainable development and harmonious regulation of the Project-Economy-Society-Environment-Energy and Resources as one complex giant system, scientists need to demonstrate them repeatedly, from the perspective of national even global, all-round, multi-level, multi-disciplinary, and not confined to a particular sector or industry. On the basis of the re-thinking analysis on large-scale engineering accidents and their related hazards, the authors think it is necessary to conclude the reasons and lessons from the failures, and establish a cross disciplinary Eco-Geological Engineering to boost the theoretical research and engineering applications of the complex giant system. Therefore, researchers can achieve the long term goal of project construction, ecological and environmental protection and sustainable economic development, instead of considering merely the site security of the project and the stability of rock mass.
2013, 21(6): 828-834.
Usually, 1Lu is considered to be the standard of terminating anti-seepage grouting in conventional pressure permeability test for the engineering of water conservancy and hydropower. With the development of science and technology, many pumped storage power stations have been or will be constructed. Test data show that permeability of rock mass is smaller using the high pressure test than that of conventional pressure permeability test. But for hydropower project with high hydraulic head, if permeability of rock mass is still calculated using 《Water Resources and Hydropower Engineering Borehole Water Pressure Test Procedures》(SL31-2003), the standard of anti-seepage grouting can be improved due to the decrease of Lu values with the increase of water pressure. For the applicability of the formula under the condition of high hydraulic head, specific water absorption of high pressure is put forward. It is defined as the injection flux of unit length with the diameter of 75mm, test section length of 5m and designed hydraulic head. It is expressed as DK with the dimension of Lmin-1m-1. Also, according to the numerical model, the injection flux of test sections for rocks is calculated. The comparison of calculated and measured injection flux is conducted in a pumped storage power station. The results show that when the high water pressure(designed hydraulic head) is 4MPa, the accepted standard of terminating anti-seepage grouting is 2DK which is correspondence to 0.5Lu. Therefore, for different hydropower projects, the standard of anti-seepage grouting needs to be changed according to the designed hydraulic head, instead of 1 Lu.
Usually, 1Lu is considered to be the standard of terminating anti-seepage grouting in conventional pressure permeability test for the engineering of water conservancy and hydropower. With the development of science and technology, many pumped storage power stations have been or will be constructed. Test data show that permeability of rock mass is smaller using the high pressure test than that of conventional pressure permeability test. But for hydropower project with high hydraulic head, if permeability of rock mass is still calculated using 《Water Resources and Hydropower Engineering Borehole Water Pressure Test Procedures》(SL31-2003), the standard of anti-seepage grouting can be improved due to the decrease of Lu values with the increase of water pressure. For the applicability of the formula under the condition of high hydraulic head, specific water absorption of high pressure is put forward. It is defined as the injection flux of unit length with the diameter of 75mm, test section length of 5m and designed hydraulic head. It is expressed as DK with the dimension of Lmin-1m-1. Also, according to the numerical model, the injection flux of test sections for rocks is calculated. The comparison of calculated and measured injection flux is conducted in a pumped storage power station. The results show that when the high water pressure(designed hydraulic head) is 4MPa, the accepted standard of terminating anti-seepage grouting is 2DK which is correspondence to 0.5Lu. Therefore, for different hydropower projects, the standard of anti-seepage grouting needs to be changed according to the designed hydraulic head, instead of 1 Lu.
2013, 21(6): 835-841.
This paper examines a large scale toppling rock slope on upper reach of the Yellow River. It is alternatively composed of countertendency bedded sandstone and thinly bedded slate. There are mainly tension cracks in the sandstone and flexural deformation in the slate. As a result of the combination of the two different time-dependent deformations, the evolution of the whole toppling rock slope is characterized as long-term, slow and progressive. Based on the combination mode of rock masses and the form of the deformation and failure, the space distribution features of the time-dependent deformation in the sandstone and slate are presented. The temporal and spatial evolution character is summarized. The mechanism of the evolution is researched. The influence of the combination mode and the structure of the rock masses as well as unloading fissure and landform during the evolution of the toppling rock slope are discussed.
This paper examines a large scale toppling rock slope on upper reach of the Yellow River. It is alternatively composed of countertendency bedded sandstone and thinly bedded slate. There are mainly tension cracks in the sandstone and flexural deformation in the slate. As a result of the combination of the two different time-dependent deformations, the evolution of the whole toppling rock slope is characterized as long-term, slow and progressive. Based on the combination mode of rock masses and the form of the deformation and failure, the space distribution features of the time-dependent deformation in the sandstone and slate are presented. The temporal and spatial evolution character is summarized. The mechanism of the evolution is researched. The influence of the combination mode and the structure of the rock masses as well as unloading fissure and landform during the evolution of the toppling rock slope are discussed.
2013, 21(6): 842-848.
An in-situ observation station is constructed to study the effects of different ground covers(asphalt, concrete, porous brock, grass and bare soil) on subsurface soil temperature and moisture. After about two years period of observation, datas of soil temperature and moisture at different depths are obtained and analyzed. The results show that the subsurface soil temperature and moisture are significantly influenced by pavement materials. The average soil temperature under artificial hard pavements(asphalt, concrete and porous brock) is much higher than that under natural covers(grass and bare soil).Especially, the subsurface soil temperature under asphalt pavement is also higher than that under porous pavement. It is also found that soil moisture under porous pavement is higher than that under asphalt and concrete pavement, while the soil moisture under natural covers is generally lower than that under artificial hard pavements. The results indicate that porous pavement is effective in retaining soil moisture and reducing soil temperature, and it is more reliable than nonporous pavement for balancing the urban thermal environment. During the urbanization process, it is therefore suggested that porous pavement material should be considered as priority option for policy makers and planners so as to improve urban ecological environment and reduce urban heat island effect.
An in-situ observation station is constructed to study the effects of different ground covers(asphalt, concrete, porous brock, grass and bare soil) on subsurface soil temperature and moisture. After about two years period of observation, datas of soil temperature and moisture at different depths are obtained and analyzed. The results show that the subsurface soil temperature and moisture are significantly influenced by pavement materials. The average soil temperature under artificial hard pavements(asphalt, concrete and porous brock) is much higher than that under natural covers(grass and bare soil).Especially, the subsurface soil temperature under asphalt pavement is also higher than that under porous pavement. It is also found that soil moisture under porous pavement is higher than that under asphalt and concrete pavement, while the soil moisture under natural covers is generally lower than that under artificial hard pavements. The results indicate that porous pavement is effective in retaining soil moisture and reducing soil temperature, and it is more reliable than nonporous pavement for balancing the urban thermal environment. During the urbanization process, it is therefore suggested that porous pavement material should be considered as priority option for policy makers and planners so as to improve urban ecological environment and reduce urban heat island effect.
2013, 21(6): 849-856.
At present, the engineering properties of unsaturated soil have become a hot topic in the geotechnical engineering field. The shear strength of unsaturated soil is particularly important for the engineering properties of soil. The authors have summarized four formulas which can forecast the shear strength of unsaturated soil using the soil water characteristic curve. The soil water characteristic curve of Majiagou Landslide Ⅰ is obtained with the five bar pressure plate instrument. The MATLAB software and Van Genuchten model are used to fit the test data. The international advanced GDS unsaturated back pressure shear apparatus(UBPS) is used to proceed the direct shear tests on the unsaturated soil. The matric suction is controlled to be 50kPa and 100kPa. The relevant shear strength is obtained. Besides, the four predicted values of soil water characteristic curve and the test result are compared. The veracity of the predictor formulas is verified. Their merits and demerits are summarized. Finally, the Fredlund's prediction formula is the most accurate one and the Huang-Runqiu's formula is the most simple and practicable.
At present, the engineering properties of unsaturated soil have become a hot topic in the geotechnical engineering field. The shear strength of unsaturated soil is particularly important for the engineering properties of soil. The authors have summarized four formulas which can forecast the shear strength of unsaturated soil using the soil water characteristic curve. The soil water characteristic curve of Majiagou Landslide Ⅰ is obtained with the five bar pressure plate instrument. The MATLAB software and Van Genuchten model are used to fit the test data. The international advanced GDS unsaturated back pressure shear apparatus(UBPS) is used to proceed the direct shear tests on the unsaturated soil. The matric suction is controlled to be 50kPa and 100kPa. The relevant shear strength is obtained. Besides, the four predicted values of soil water characteristic curve and the test result are compared. The veracity of the predictor formulas is verified. Their merits and demerits are summarized. Finally, the Fredlund's prediction formula is the most accurate one and the Huang-Runqiu's formula is the most simple and practicable.
2013, 21(6): 857-863.
The model test material of collapsible loess is the bottleneck of similar material model research in geomechanics, which has limited application of model tests in loess area. A similar material of model test for collapsible loess is developed by airfall technique based on Monte Carlo method. A single pile foundation model test is carried out to investigate the negative skin friction of the pile under the effect of self-weight collapsibility. The research results show that the axial force along the pile of different time roughly appeared as the shape of B.The neutral point is located between the modeled collapsible soil and sands. The settlement of the top of pile is far less than collapse deformation of the soil due to the effect of self-weight collapsibility. The negative frictional resistance of the pile increases along the depth and reaches the peak at the neutral point. The frictional resistance along the pile roughly appears as the shape of Dwhen immersing water for 1 hour. Through out the testing phase, the negative friction reaches a second peak and the curve distributes as the shape of . The settlement of the top of pile is about 0.54mm due to the frictional resistance. The experimental research methods and results can provide references for similar projects.
The model test material of collapsible loess is the bottleneck of similar material model research in geomechanics, which has limited application of model tests in loess area. A similar material of model test for collapsible loess is developed by airfall technique based on Monte Carlo method. A single pile foundation model test is carried out to investigate the negative skin friction of the pile under the effect of self-weight collapsibility. The research results show that the axial force along the pile of different time roughly appeared as the shape of B.The neutral point is located between the modeled collapsible soil and sands. The settlement of the top of pile is far less than collapse deformation of the soil due to the effect of self-weight collapsibility. The negative frictional resistance of the pile increases along the depth and reaches the peak at the neutral point. The frictional resistance along the pile roughly appears as the shape of Dwhen immersing water for 1 hour. Through out the testing phase, the negative friction reaches a second peak and the curve distributes as the shape of . The settlement of the top of pile is about 0.54mm due to the frictional resistance. The experimental research methods and results can provide references for similar projects.
2013, 21(6): 864-870.
This paper presents laboratory tests for lime as modifying agent in compaction of expansive soils. The expansive soil samples are from the proposed airport location at An-Kang. The CSK-V1 multi-function electric compaction instrument is used in laboratory for heavy compaction tests. A series of compaction characteristic tests are conducted. Findings are as follows:(1)As lime dosage increases, the maximum dry density decreases, and the optimum water content increases.(2)In the vicinity of the optimal water content, as lime dosage increases, the effect of water content on dry density decreases.(3)The higher soil height, the smaller dry density in the condition of the same compaction work, lime dosage and water content.(4)Maximum dry density tends to decrease steadily as braised material time increases, which changes little after 48h. (5)The order of main influential factors of dry density is water content, the materials humectation time and the excess soil height with the same kind of lime dosage. Finally, depending on the Scanning Electron Microscope(SEM),the lime-treated expansive soil and compaction test are described and analyzed from the microscopic point of view.
This paper presents laboratory tests for lime as modifying agent in compaction of expansive soils. The expansive soil samples are from the proposed airport location at An-Kang. The CSK-V1 multi-function electric compaction instrument is used in laboratory for heavy compaction tests. A series of compaction characteristic tests are conducted. Findings are as follows:(1)As lime dosage increases, the maximum dry density decreases, and the optimum water content increases.(2)In the vicinity of the optimal water content, as lime dosage increases, the effect of water content on dry density decreases.(3)The higher soil height, the smaller dry density in the condition of the same compaction work, lime dosage and water content.(4)Maximum dry density tends to decrease steadily as braised material time increases, which changes little after 48h. (5)The order of main influential factors of dry density is water content, the materials humectation time and the excess soil height with the same kind of lime dosage. Finally, depending on the Scanning Electron Microscope(SEM),the lime-treated expansive soil and compaction test are described and analyzed from the microscopic point of view.
2013, 21(6): 871-877.
Along with the development of city underground space, the place where buried depth of underground water is low, like Shenyang, dewatering is needed during construction and water level is recovered after completion. Frequent water level change can lead to many geotechnical problems such as bearing capacity change, surface collapse caused by additional settlement of foundation and seepage flow in soil. Especially the bearing capacity and the additional settlement are key problems. Many researches and papers only supply the qualitative results. The purpose of this paper is to get the quantitative results. This paper is based on the model test. It builds a foundation model on the coarse sand, through the SLT test, monitoring the water level and the stress change using the soil pressure sensor and water pressure sensor, and recording the bearing capacity, settlement and stress change along with the water level change. Then conducted numerical analysis, and used fitting formula to settle the relationship of model test and numerical analysis. The results show that the coarse foundation base characteristic value can lose 26% in max after the water level change. If load is applied on the foundation either the water level up or down can cause additional settlement. If the water level rises 4.3m, the additional settlement can be 0.565mm(caused by bearing capacity drop). If the water level drops 4.3m, the additional settlement can be 0.315mm(caused by the increase of effective stress). Numerical analysis shows that for dry sand the numerical analysis fit well. For saturated sand, the tolerance can be fixed by the fitting formula.
Along with the development of city underground space, the place where buried depth of underground water is low, like Shenyang, dewatering is needed during construction and water level is recovered after completion. Frequent water level change can lead to many geotechnical problems such as bearing capacity change, surface collapse caused by additional settlement of foundation and seepage flow in soil. Especially the bearing capacity and the additional settlement are key problems. Many researches and papers only supply the qualitative results. The purpose of this paper is to get the quantitative results. This paper is based on the model test. It builds a foundation model on the coarse sand, through the SLT test, monitoring the water level and the stress change using the soil pressure sensor and water pressure sensor, and recording the bearing capacity, settlement and stress change along with the water level change. Then conducted numerical analysis, and used fitting formula to settle the relationship of model test and numerical analysis. The results show that the coarse foundation base characteristic value can lose 26% in max after the water level change. If load is applied on the foundation either the water level up or down can cause additional settlement. If the water level rises 4.3m, the additional settlement can be 0.565mm(caused by bearing capacity drop). If the water level drops 4.3m, the additional settlement can be 0.315mm(caused by the increase of effective stress). Numerical analysis shows that for dry sand the numerical analysis fit well. For saturated sand, the tolerance can be fixed by the fitting formula.
2013, 21(6): 878-884.
Landslides of quaternary deposits along the gentle bedrock-cover interface frequently occur during the construction of Bazhong-Dazhou-Wanzhou expressway. Strengths of unsaturated soils affected by groundwater and excavation are the two main factors of the landslides. On the basis of unsaturated direct-shear tests, the unsaturated-analysis soft wares of SEEP/W and SIGMA/W are used in the analysis of sliding mechanism. The results shows that distribution of groundwater seepage produces the soft soil along the bedrock-cover interface. The distribution of groundwater seepage leads to the distribution of matric suction which causes the deterioration of shear strength from top to bottom. Eventually, the soft soil with the weakest strength distributed along the bedrock-cover interface. With the cutting of the deposits with horizontal beddings, the soft soil apparently surrenders and deforms. Tension failures appear at the back of landslide; the middle part of landslide creeps along the bedrock-cover interface; shear-compression occurs in the front of landslide; and groundwater gradually dissipates.
Landslides of quaternary deposits along the gentle bedrock-cover interface frequently occur during the construction of Bazhong-Dazhou-Wanzhou expressway. Strengths of unsaturated soils affected by groundwater and excavation are the two main factors of the landslides. On the basis of unsaturated direct-shear tests, the unsaturated-analysis soft wares of SEEP/W and SIGMA/W are used in the analysis of sliding mechanism. The results shows that distribution of groundwater seepage produces the soft soil along the bedrock-cover interface. The distribution of groundwater seepage leads to the distribution of matric suction which causes the deterioration of shear strength from top to bottom. Eventually, the soft soil with the weakest strength distributed along the bedrock-cover interface. With the cutting of the deposits with horizontal beddings, the soft soil apparently surrenders and deforms. Tension failures appear at the back of landslide; the middle part of landslide creeps along the bedrock-cover interface; shear-compression occurs in the front of landslide; and groundwater gradually dissipates.
2013, 21(6): 885-891.
Real-time monitoring system about surface and deep displacement of landslide is the relative displacement measurement instrument. On the basis of field investigation, the geologic environment and characters of Shengli landslide are studied in detail in this paper. Geologic origin and the environment origin are examined. The geological structure type(sand+clay+sandy mudstone) is the crucial factor. Continuing excavation, exploding and applied loading are the influencing factors. The high intense and large rainfall is the triggering factor. By analyzing surface and deep displacement monitoring data, the rate of surface displacement is 1mmd-1 three months before the rainstorm, at the stage of uniform creep stage. It appears traction landslide characteristics. At the same time, the deep displacement remains unchanged. After the rainstorm, both surface and deep displacements increase suddenly. Three deep displacement monitoring points with different depths effectively capture the approximate locations of the slip surface and dislocation distance, which can provide reference for determining the depth of deep displacement monitoring.
Real-time monitoring system about surface and deep displacement of landslide is the relative displacement measurement instrument. On the basis of field investigation, the geologic environment and characters of Shengli landslide are studied in detail in this paper. Geologic origin and the environment origin are examined. The geological structure type(sand+clay+sandy mudstone) is the crucial factor. Continuing excavation, exploding and applied loading are the influencing factors. The high intense and large rainfall is the triggering factor. By analyzing surface and deep displacement monitoring data, the rate of surface displacement is 1mmd-1 three months before the rainstorm, at the stage of uniform creep stage. It appears traction landslide characteristics. At the same time, the deep displacement remains unchanged. After the rainstorm, both surface and deep displacements increase suddenly. Three deep displacement monitoring points with different depths effectively capture the approximate locations of the slip surface and dislocation distance, which can provide reference for determining the depth of deep displacement monitoring.
2013, 21(6): 892-897.
The grillage supporting structure with anchor bars applied to loess slope is a new type of slope protection and reinforcement method. In this paper, the rational calculation models of the soil pressure, the grillage supporting structure and anchor bars are selected, and calculation elements of horizontal beams and vertical columns are emphasized. It also points out that beams and columns not only bear the uniform load in the beam cross section, but also bear the triangular or trapezoidal load passed from adjacent retaining plate. It is the superposition of the two components. Finally, a loess slope is designed and analyzed. The results show that this method is both safe and reliable and has a better economic applicability.
The grillage supporting structure with anchor bars applied to loess slope is a new type of slope protection and reinforcement method. In this paper, the rational calculation models of the soil pressure, the grillage supporting structure and anchor bars are selected, and calculation elements of horizontal beams and vertical columns are emphasized. It also points out that beams and columns not only bear the uniform load in the beam cross section, but also bear the triangular or trapezoidal load passed from adjacent retaining plate. It is the superposition of the two components. Finally, a loess slope is designed and analyzed. The results show that this method is both safe and reliable and has a better economic applicability.
2013, 21(6): 898-907.
The number of buried ground fissures is much more than that of exposed ones. The buried ground fissures have brought about great hazards and thus attracted more attentions. Rupture propagation modes of buried ground fissures are affected by many factors including the displacement, inclination and activity rate of ground fissures, the properties, thickness and strata structure of overlying soil, as well as surface-water infiltration, groundwater exploitation, ground motion and time effects. The different combinations of these factors result in the complex mechanical mechanism of rupture propagation over buried ground fissures and make it difficult to reproduce the rupture propagation process. Currently, research methods of the rupture propagation are mainly about in-situ investigation and exploration, model test, mechanical analysis and numerical simulation. The research contents focus on the rupture propagation effect based on the change of single formation condition or inducing factor. Such future priority research subjects include 1)analyzing comprehensive effects and mechanical mechanism of rupture propagation under its formation geological conditions, multi-stage activity, long-term creeping motion and a variety of inducing factors, 2)studying on the rupture propagation process to track the fracture position and its influence width at a different depth, 3)calculating the maximum vertical surface displacement caused by rupture propagation and the minimum safe overburden thickness under certain conditions, and 4)determining unified methods and standards for the effect zone width of ground fissure. All these research subjects can use to interpret the actual fracture phenomena and provide the basis for the comprehensive prevention and control of ground fissures.
The number of buried ground fissures is much more than that of exposed ones. The buried ground fissures have brought about great hazards and thus attracted more attentions. Rupture propagation modes of buried ground fissures are affected by many factors including the displacement, inclination and activity rate of ground fissures, the properties, thickness and strata structure of overlying soil, as well as surface-water infiltration, groundwater exploitation, ground motion and time effects. The different combinations of these factors result in the complex mechanical mechanism of rupture propagation over buried ground fissures and make it difficult to reproduce the rupture propagation process. Currently, research methods of the rupture propagation are mainly about in-situ investigation and exploration, model test, mechanical analysis and numerical simulation. The research contents focus on the rupture propagation effect based on the change of single formation condition or inducing factor. Such future priority research subjects include 1)analyzing comprehensive effects and mechanical mechanism of rupture propagation under its formation geological conditions, multi-stage activity, long-term creeping motion and a variety of inducing factors, 2)studying on the rupture propagation process to track the fracture position and its influence width at a different depth, 3)calculating the maximum vertical surface displacement caused by rupture propagation and the minimum safe overburden thickness under certain conditions, and 4)determining unified methods and standards for the effect zone width of ground fissure. All these research subjects can use to interpret the actual fracture phenomena and provide the basis for the comprehensive prevention and control of ground fissures.
2013, 21(6): 908-911.
A relatively low correlation appeared between the result from the published paper of Wang Tao et al. named Case study on rapid assessment of regional seismic landslide hazard based on simplified Newmark displacement model: Wenchuan MS8.0 earthquake and spatial distribution pattern of actual landslides triggered by the 2008 Wenchuan earthquake. The main purpose of this comment or discussion is to analyze the reasons of the low correlation by analyzing and discussing of basic data, data analysis process, and results from that paper from Wang Tao and his research teams. The results suggest that Wang Tao and his teams carry out a more in-depth study in three aspects, include accuracy of the Arias intensity data, engineering geology lithology formation groupings, and validation of the Wenchuan earthquake-triggered landslides hazard assessment. This comment plays a positive role on exploring more scientific landslide hazard assessment models.
A relatively low correlation appeared between the result from the published paper of Wang Tao et al. named Case study on rapid assessment of regional seismic landslide hazard based on simplified Newmark displacement model: Wenchuan MS8.0 earthquake and spatial distribution pattern of actual landslides triggered by the 2008 Wenchuan earthquake. The main purpose of this comment or discussion is to analyze the reasons of the low correlation by analyzing and discussing of basic data, data analysis process, and results from that paper from Wang Tao and his research teams. The results suggest that Wang Tao and his teams carry out a more in-depth study in three aspects, include accuracy of the Arias intensity data, engineering geology lithology formation groupings, and validation of the Wenchuan earthquake-triggered landslides hazard assessment. This comment plays a positive role on exploring more scientific landslide hazard assessment models.
2013, 21(6): 912-919.
The condition and gradient of the slope, the block shape and mass of the rock block are the major factors affecting the movement characteristics of rock-fall. Through the orthogonal test design(L27(34)),the sort of them is obtained: slope condition X1,rock block shape X2,slope gradient X3,rock block mass X4.The velocity estimation values of rock-fall are calculated with the velocity equation v=-7.85X10.50+0.47X23.22+2.97X30.24.This equation is established by regression analysis. The values are compared with the measured values. The results show that the relative error is only 8.2% and the correlation coefficient is r=0.92. Trend impact of regression equation analysis of the single factor shows that the slope condition has significantly negative linear correlation relationship with the speed of rock block. The mathematical relationship between the rock block shape and speed is sunken curve. The slope gradient and speed is convex curve. They are the same as the analysis of the empirical formula. Through rock-fall field test and based on the measurement, a simplified modified velocity formula is v =v0+(L/2.45)vc.By comparison, it is in good agreement with the measured results. It proves the applicability and validity of the formula given in this paper. The results can be used in estimating the speed and the impact energy of the rock-fall, and have a certain reference value in choosing prevention and control measures of rock-fall.
The condition and gradient of the slope, the block shape and mass of the rock block are the major factors affecting the movement characteristics of rock-fall. Through the orthogonal test design(L27(34)),the sort of them is obtained: slope condition X1,rock block shape X2,slope gradient X3,rock block mass X4.The velocity estimation values of rock-fall are calculated with the velocity equation v=-7.85X10.50+0.47X23.22+2.97X30.24.This equation is established by regression analysis. The values are compared with the measured values. The results show that the relative error is only 8.2% and the correlation coefficient is r=0.92. Trend impact of regression equation analysis of the single factor shows that the slope condition has significantly negative linear correlation relationship with the speed of rock block. The mathematical relationship between the rock block shape and speed is sunken curve. The slope gradient and speed is convex curve. They are the same as the analysis of the empirical formula. Through rock-fall field test and based on the measurement, a simplified modified velocity formula is v =v0+(L/2.45)vc.By comparison, it is in good agreement with the measured results. It proves the applicability and validity of the formula given in this paper. The results can be used in estimating the speed and the impact energy of the rock-fall, and have a certain reference value in choosing prevention and control measures of rock-fall.
2013, 21(6): 920-925.
Loess collapse is the common disaster in loess area, and influences the safety of human's life and production. According to the survey on site, it is believed that the main internal causes of loess collapse formation are the characteristics of loess soil and the joint cutting level, and the main external causes are the function of rainfall, human activity and biological activity. In terms of the common form of movement for loess collapse, the theory formula that determines the range of collapse body is presented under the condition that the collapse body falls freely and rolls. The example calculations show that, at the base of the ground level, no matter what the movement it is,the influence range of collapsing is 0.4～0.6 times of the slope height. As the slope steepens, the ratio for sliding distance and the slope height is enlarged accordingly. When the collapse body falls freely, the influence range of the collapse body has a relationship with the gradient of the collision point. When the collapse body slides in the slope, the influence range of collapse body has a relationship with the degree of slope. Research results can be used as the forecasting methods for the disaster range caused by loess collapse in loess area, which provides the theoretical basis for preventing loess collapse.
Loess collapse is the common disaster in loess area, and influences the safety of human's life and production. According to the survey on site, it is believed that the main internal causes of loess collapse formation are the characteristics of loess soil and the joint cutting level, and the main external causes are the function of rainfall, human activity and biological activity. In terms of the common form of movement for loess collapse, the theory formula that determines the range of collapse body is presented under the condition that the collapse body falls freely and rolls. The example calculations show that, at the base of the ground level, no matter what the movement it is,the influence range of collapsing is 0.4～0.6 times of the slope height. As the slope steepens, the ratio for sliding distance and the slope height is enlarged accordingly. When the collapse body falls freely, the influence range of the collapse body has a relationship with the gradient of the collision point. When the collapse body slides in the slope, the influence range of collapse body has a relationship with the degree of slope. Research results can be used as the forecasting methods for the disaster range caused by loess collapse in loess area, which provides the theoretical basis for preventing loess collapse.
2013, 21(6): 926-931.
In-situ leaching uranium mining using acid solutions has a great impact on groundwater environment, leaving acid plumes in groundwater after mining activities. Effective measures should be taken to restore the water quality in mining aquifers. Natural attenuation is an economical method. But the effectiveness should be evaluated before using this remediation method. In this study, natural attenuation of an acid plume in a shutdown uranium site is simulated using reactive transport modeling method. PHT3D is used to construct the model, including advective-dispersive transport, aqueous speciation of 12 components, and precipitation-dissolution of six minerals. The model has a whole simulation time of 5 years. Simulation results show that: successive pH buffer reactions with calcite, Al(OH)3(a) and Fe(OH)3(a) create distinct geochemical zones. With the high pH environmental downstream, concentration of SO42- decreases significantly related to calcite dissolution and gypsum precipitation reactions. Most metal ion contaminants also have an attenuation process.
In-situ leaching uranium mining using acid solutions has a great impact on groundwater environment, leaving acid plumes in groundwater after mining activities. Effective measures should be taken to restore the water quality in mining aquifers. Natural attenuation is an economical method. But the effectiveness should be evaluated before using this remediation method. In this study, natural attenuation of an acid plume in a shutdown uranium site is simulated using reactive transport modeling method. PHT3D is used to construct the model, including advective-dispersive transport, aqueous speciation of 12 components, and precipitation-dissolution of six minerals. The model has a whole simulation time of 5 years. Simulation results show that: successive pH buffer reactions with calcite, Al(OH)3(a) and Fe(OH)3(a) create distinct geochemical zones. With the high pH environmental downstream, concentration of SO42- decreases significantly related to calcite dissolution and gypsum precipitation reactions. Most metal ion contaminants also have an attenuation process.
2013, 21(6): 932-937.
Reservoir induced earthquakes of large-scale hydropower project have always a concern of owners and technical personnel. The Three Gorges reservoir has been impounded for 10 years, and the earthquake frequency in the reservoir increases significantly during the impoundment. An area near the dam site and with active faults, carbonatite and coal seams is chosen as the research object. Analyze the spatial distribution of reservoir induced earthquakes and the relationship between earthquake and reservoir water level. The analysis results indicate that 90% of the reservoir induced earthquakes are collapsing induced by earthquakes which occurred in carbonatite and coal seams. The other 10%occurred in other stratums. It also indicates that the attitude of stratum has a significant effect on reservoir induced earthquakes. The earthquakes near the dam site have clustering distribution characteristic, which mainly occurred at the northern part of Xiannvshan Fault. Some earthquakes occurred in the hanging wall of Jiuwanxi fault, which occurred more at the nearby site of Yangtze river and less in the faraway site, while rarely occurred in the heading wall of the fault. The reservoir induced earthquakes and reservoir water level are closely related. While the water level of Three Gorges reservoir rises, many small earthquakes occur on both sides of Yangtze river. When the water level rises to 175m, most of the earthquakes occur in the northern part of Xiannvshan fault and the hanging wall of Jiuwanxi fault.
Reservoir induced earthquakes of large-scale hydropower project have always a concern of owners and technical personnel. The Three Gorges reservoir has been impounded for 10 years, and the earthquake frequency in the reservoir increases significantly during the impoundment. An area near the dam site and with active faults, carbonatite and coal seams is chosen as the research object. Analyze the spatial distribution of reservoir induced earthquakes and the relationship between earthquake and reservoir water level. The analysis results indicate that 90% of the reservoir induced earthquakes are collapsing induced by earthquakes which occurred in carbonatite and coal seams. The other 10%occurred in other stratums. It also indicates that the attitude of stratum has a significant effect on reservoir induced earthquakes. The earthquakes near the dam site have clustering distribution characteristic, which mainly occurred at the northern part of Xiannvshan Fault. Some earthquakes occurred in the hanging wall of Jiuwanxi fault, which occurred more at the nearby site of Yangtze river and less in the faraway site, while rarely occurred in the heading wall of the fault. The reservoir induced earthquakes and reservoir water level are closely related. While the water level of Three Gorges reservoir rises, many small earthquakes occur on both sides of Yangtze river. When the water level rises to 175m, most of the earthquakes occur in the northern part of Xiannvshan fault and the hanging wall of Jiuwanxi fault.
2013, 21(6): 938-949.
Landslide mechanism is the key of understanding, reasonable assessment, effective prevention and control of landslides. It is quite difficult to achieve. Meanwhile, loess landslide mechanism has been one of the research hotspots in Chinese engineering geological circles over last decades. This study carries out detailed landslide survey and inventory combined with typical large scale slide drilling and geophysical exploration at the edge of loess plateau on north of Weihe river in Baoji urban area. There have been quite many achievements on latest quaternary geology, tectonic geology and loess studies in the recent years. The Weihe river valley evolution process is rebuilt. The slope structure and lithological association with engineering geological characteristics of stratigraphic which prone to failure are carried out. Active fault and tectonic joints or fissures are investigated as well. This study reveals the follows. The paleogeomorphology of north side of Weihe river is higher than the south part. The north land changed to the south Sanmen lake basin during Pliocene to early Pleistocene. Then the south lake basin gradually retreated and the Weihe river formed in early Pleistocene. The Weihe river mainstream periodicity north offset due to neotectonic movement and periodic climate change until Holocene epoch, and then gradually south offset. Hence, the present geomorphologic pattern is formed. The active Weihe north fault at the edge of loess plateau by sub-graben, horst bulge and half-graben provides not only water infiltration channels but also weak structure planes for slide failure surfaces tracking. The cause and model of paleo-slide and old-slide at the edge of loess plateau are induced by integrated erosion and rising of groundwater table. The main or sub-scarp and failure surface tracking along active fractures and Pliocene sand gravel and clay interface or internal clay are featured by garben-horst style multiple deep-seated rotational slide or multiple perched translational slide and its combination. They are controlled by Pliocene clay and tectonic fractures. They are special complex slides in loess landslides.
Landslide mechanism is the key of understanding, reasonable assessment, effective prevention and control of landslides. It is quite difficult to achieve. Meanwhile, loess landslide mechanism has been one of the research hotspots in Chinese engineering geological circles over last decades. This study carries out detailed landslide survey and inventory combined with typical large scale slide drilling and geophysical exploration at the edge of loess plateau on north of Weihe river in Baoji urban area. There have been quite many achievements on latest quaternary geology, tectonic geology and loess studies in the recent years. The Weihe river valley evolution process is rebuilt. The slope structure and lithological association with engineering geological characteristics of stratigraphic which prone to failure are carried out. Active fault and tectonic joints or fissures are investigated as well. This study reveals the follows. The paleogeomorphology of north side of Weihe river is higher than the south part. The north land changed to the south Sanmen lake basin during Pliocene to early Pleistocene. Then the south lake basin gradually retreated and the Weihe river formed in early Pleistocene. The Weihe river mainstream periodicity north offset due to neotectonic movement and periodic climate change until Holocene epoch, and then gradually south offset. Hence, the present geomorphologic pattern is formed. The active Weihe north fault at the edge of loess plateau by sub-graben, horst bulge and half-graben provides not only water infiltration channels but also weak structure planes for slide failure surfaces tracking. The cause and model of paleo-slide and old-slide at the edge of loess plateau are induced by integrated erosion and rising of groundwater table. The main or sub-scarp and failure surface tracking along active fractures and Pliocene sand gravel and clay interface or internal clay are featured by garben-horst style multiple deep-seated rotational slide or multiple perched translational slide and its combination. They are controlled by Pliocene clay and tectonic fractures. They are special complex slides in loess landslides.
2013, 21(6): 950-958.
Based on the characteristics and distribution of quicksand in Shanghai, this paper presented an index system for quicksand risk assessment, aiming of risk assessment, zoning and management division of quicksand. First, according to the spatial distribution characteristics of ②3, ⑤2 and ⑦ silty-sandy soil layers, the danger analysis and zoning of quicksand are carried out. Second, based on administrative division and comprehensive consideration of socio-economic statistical indicators, the vulnerability analysis and zoning of quicksand are made. And on that basis, the risk comprehensive evaluation and division are conducted. Finally, risk control and management zoning of quicksand during the 12th five-year planning are presented by combining the content on economic and urban key projects of outline of the 12th five-year planning for economic and social development of Shanghai. The results of this paper can provide guidance and geological basis for possible quicksand's monitoring, prediction and prevention during underground construction(excavation, subway tunnels, underground supermarket, etc.),including investigation, design, construction, and provide decision-making reference for management departments.
Based on the characteristics and distribution of quicksand in Shanghai, this paper presented an index system for quicksand risk assessment, aiming of risk assessment, zoning and management division of quicksand. First, according to the spatial distribution characteristics of ②3, ⑤2 and ⑦ silty-sandy soil layers, the danger analysis and zoning of quicksand are carried out. Second, based on administrative division and comprehensive consideration of socio-economic statistical indicators, the vulnerability analysis and zoning of quicksand are made. And on that basis, the risk comprehensive evaluation and division are conducted. Finally, risk control and management zoning of quicksand during the 12th five-year planning are presented by combining the content on economic and urban key projects of outline of the 12th five-year planning for economic and social development of Shanghai. The results of this paper can provide guidance and geological basis for possible quicksand's monitoring, prediction and prevention during underground construction(excavation, subway tunnels, underground supermarket, etc.),including investigation, design, construction, and provide decision-making reference for management departments.
2013, 21(6): 959-966.
Swelling potential of expansive soil is controlled by many factors. So quantitative classification of expansive soil is always a problem and is not solved well. This paper takes the expansive soil in the Water Transfer Project from the Yangtze River to Han River in middle scheme of the South-to-North Water Diversion Project as the research object. Through analysis of experimental datas, this paper gives the suggested value of classification standard of the expansive soil. Based on three mathematical methods of artificial neural network model, the Fisher's discriminant analysis and rough sets theory, comprehensive indexes are used to analyze the swelling potential of 40 expansive soil samples. This paper determines the final classification results through comparative study of the three mathematical methods. According to the classification results and operation method of each mathematical method, based on the theory of relatively simple, easy to operate and easy to accept, this paper suggests that the Fisher's discriminant analysis can be a priority to analyze the swelling potential of expansive soil. In addition, this paper also gives the suggested value of classification standard of montmorillonite content, which verifies the correctness of classification results. The results of this paper provide a theoretical basis for the identification and classification of expansive soil in the process of the rest of excavation.
Swelling potential of expansive soil is controlled by many factors. So quantitative classification of expansive soil is always a problem and is not solved well. This paper takes the expansive soil in the Water Transfer Project from the Yangtze River to Han River in middle scheme of the South-to-North Water Diversion Project as the research object. Through analysis of experimental datas, this paper gives the suggested value of classification standard of the expansive soil. Based on three mathematical methods of artificial neural network model, the Fisher's discriminant analysis and rough sets theory, comprehensive indexes are used to analyze the swelling potential of 40 expansive soil samples. This paper determines the final classification results through comparative study of the three mathematical methods. According to the classification results and operation method of each mathematical method, based on the theory of relatively simple, easy to operate and easy to accept, this paper suggests that the Fisher's discriminant analysis can be a priority to analyze the swelling potential of expansive soil. In addition, this paper also gives the suggested value of classification standard of montmorillonite content, which verifies the correctness of classification results. The results of this paper provide a theoretical basis for the identification and classification of expansive soil in the process of the rest of excavation.
2013, 21(6): 967-972.
The consolidation undrained triaxial shear creep tests are performed on Dezhou soft soil under different confining pressures with TSS10 rheometer. The relationships of axial strain and creep stain rate with stress and time are obtained. The effect of soft soil property on its creep behavior is analyzed. The extended Maxwell model is established. The results show that nonlinear creep characteristic is obviously described by creep deformation of Dezhou soft soil. The creep deformation in the range of high deviatoric stress is greater than that in the range of low deviatoric stress. Fractional creep element theory is introduced. The fractional extended Maxwell model is advised. The extended Maxwell model parameters of Dezhou soft soil are solved, which can predict creep deformation of Dezhou soft soil well.
The consolidation undrained triaxial shear creep tests are performed on Dezhou soft soil under different confining pressures with TSS10 rheometer. The relationships of axial strain and creep stain rate with stress and time are obtained. The effect of soft soil property on its creep behavior is analyzed. The extended Maxwell model is established. The results show that nonlinear creep characteristic is obviously described by creep deformation of Dezhou soft soil. The creep deformation in the range of high deviatoric stress is greater than that in the range of low deviatoric stress. Fractional creep element theory is introduced. The fractional extended Maxwell model is advised. The extended Maxwell model parameters of Dezhou soft soil are solved, which can predict creep deformation of Dezhou soft soil well.
2013, 21(6): 973-980.
Soil structure is the main reason causing the differences between natural and remolded soils. The soil structure have impacts on methods and means of geotechnical engineering. This paper establishes a structural constitutive model of Haikou red clay. Based on structural quantitative indicators, the concept of comprehensive structure potential is introduced. It builds quantitative expression among geotechnical microstructure, cementation and macroscopic mechanical effects. The stress typical structural parameter and strain typical structural parameter are defined. They are obtained through the isotropic consolidation test and p=constant shearing test respectively. Both parameters exist the normalized linearization relationship relative to average principal stress. The result can describe the Haikou undisturbed red clay structure. These parameters are used to modify the K-G model. A numerical simulation is carried out. Results showed that the modified K-G model can describe the structure of Haikou undisturbed red clay, and well predict the stress-strain relationship of undisturbed red soil.
Soil structure is the main reason causing the differences between natural and remolded soils. The soil structure have impacts on methods and means of geotechnical engineering. This paper establishes a structural constitutive model of Haikou red clay. Based on structural quantitative indicators, the concept of comprehensive structure potential is introduced. It builds quantitative expression among geotechnical microstructure, cementation and macroscopic mechanical effects. The stress typical structural parameter and strain typical structural parameter are defined. They are obtained through the isotropic consolidation test and p=constant shearing test respectively. Both parameters exist the normalized linearization relationship relative to average principal stress. The result can describe the Haikou undisturbed red clay structure. These parameters are used to modify the K-G model. A numerical simulation is carried out. Results showed that the modified K-G model can describe the structure of Haikou undisturbed red clay, and well predict the stress-strain relationship of undisturbed red soil.
2013, 21(6): 981-986.
In the landfill, liner systems typically contain a large number of material interfaces(soil/geomembrane or geomembrane/geosynthetics). These interfaces become potential slip surfaces because of the low shear strength, which results in the instability of landfill. Based on many direct shear tests, the deformation mechanism and strain softening property of soil/geomembrane interface, the interface thickness, tangential strain and normal strain are determined. The deformation of the interface is divided into three stages: elastic stage, plastic stage and residual stage. Above all, the elastic-plastic interface constitutive model is put forward. There are only a few parameters with clear physical meanings in the model. At last, the results using this model are compared with those of the interface direct shear tests and ring simple shear tests. The comparison results show that this model is reasonable and feasible, and can be used for practical engineering.
In the landfill, liner systems typically contain a large number of material interfaces(soil/geomembrane or geomembrane/geosynthetics). These interfaces become potential slip surfaces because of the low shear strength, which results in the instability of landfill. Based on many direct shear tests, the deformation mechanism and strain softening property of soil/geomembrane interface, the interface thickness, tangential strain and normal strain are determined. The deformation of the interface is divided into three stages: elastic stage, plastic stage and residual stage. Above all, the elastic-plastic interface constitutive model is put forward. There are only a few parameters with clear physical meanings in the model. At last, the results using this model are compared with those of the interface direct shear tests and ring simple shear tests. The comparison results show that this model is reasonable and feasible, and can be used for practical engineering.
2013, 21(6): 987-994.
This paper mainly introduces the application of the Controlled Source Audio Frequency Magnetotelluric Sounding(CSAMT) in bauxite investigation and evaluation project of Henan Xinanshi Temple and Beiye region. It used the V8 multifunctional electrical workstation. The CSAMT method have the characteristics such as strong anti-interference ability, greater probing depth and mature means of data interpretation. It plays a critical role in the project of bauxite survey and evaluation. It clearly reflects the bauxite ore target layer in the investigation area, the Ordovician weathering crust morphology variation along the strike and stratigraphic occurrence. Provide the deep electrical information for stratigraphic division and subsequent bauxite survey and evaluation work, and provide the basis for drilling design and prediction of mineral resources.
This paper mainly introduces the application of the Controlled Source Audio Frequency Magnetotelluric Sounding(CSAMT) in bauxite investigation and evaluation project of Henan Xinanshi Temple and Beiye region. It used the V8 multifunctional electrical workstation. The CSAMT method have the characteristics such as strong anti-interference ability, greater probing depth and mature means of data interpretation. It plays a critical role in the project of bauxite survey and evaluation. It clearly reflects the bauxite ore target layer in the investigation area, the Ordovician weathering crust morphology variation along the strike and stratigraphic occurrence. Provide the deep electrical information for stratigraphic division and subsequent bauxite survey and evaluation work, and provide the basis for drilling design and prediction of mineral resources.
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