Online Submission
Manuscript Tracking
Peer Review
Editor Work2015 Vol. 23, No. 1
Previous Issue
2015, 23(1): 1-6.
Abstract
438KB
This is a summary of the 2014 annual symposium of engineering geology in Taiyuan. The meeting gathered around 800 experts and scholars at the topic of the Major Engineering Geological Issues Induced by Resources Development. Through 15 invited lectures, 69 speeches in 3 sessions and the papers published in the proceedings, the meeting has reflected the state of art of engineering geology in China with the following features: (1)Touch the frontier of the discipline; (2)Provide technical supports to the regional economic development; (3)More internationalized and popularized with the active participation of enterprises; (4)Strongly promoted by the application of new technology; (5)Young professionals act as a vital force in the academic stage, and (6)Philosophical thinking makes the engineering geologists entered a new realm. The paper also pointed out the challenges to engineering geology in Chinese, firstly the gap between the poor fundamental research and the demand of the industry; secondly the urgency for the reconstruction of discipline spirit.
This is a summary of the 2014 annual symposium of engineering geology in Taiyuan. The meeting gathered around 800 experts and scholars at the topic of the Major Engineering Geological Issues Induced by Resources Development. Through 15 invited lectures, 69 speeches in 3 sessions and the papers published in the proceedings, the meeting has reflected the state of art of engineering geology in China with the following features: (1)Touch the frontier of the discipline; (2)Provide technical supports to the regional economic development; (3)More internationalized and popularized with the active participation of enterprises; (4)Strongly promoted by the application of new technology; (5)Young professionals act as a vital force in the academic stage, and (6)Philosophical thinking makes the engineering geologists entered a new realm. The paper also pointed out the challenges to engineering geology in Chinese, firstly the gap between the poor fundamental research and the demand of the industry; secondly the urgency for the reconstruction of discipline spirit.
EXPERIMENTAL STUDY ON EFFECT OF SHEARING RATE ON MECHANICAL BEHAVIOR OF STRUCTURED SOFT DREDGER FILL
2015, 23(1): 7-12.
In clay shear deformation process, different shear rates have different effects on its structural damage, thus affecting its mechanical behavior. This paper takes the soft dredger fill from Tianjin Binhai New Area as research object. It discusses the structural about soft dredger fill, and carries out the triaxial shear tests to study effects on mechanical behavior caused by different shear rates, analyzes its mechanical effect of shearing rate. The test result indicates that as the shear rate increases, at low confining pressure condition, the strength and structural yield stress of soft dredger fill increase at first and then decrease, existing a critical shear rate. At high confining pressure condition, the strength and structural yield stress increase gradually, which shows a positive correlation with the shearing rate. The critical rate is disappearing gradually. However, at different confining pressure conditions, the cohesion of dredger fill decreases as the shearing rate increases. As the shearing rate increases, the internal friction angle shows an increasing trend at low confining pressure condition, which shows a decreasing trend at high confining pressure condition. In the shearing process, pore water pressure increases with the increase of axial strain to a certain value, and then becomes stable. With further increase of confining pressure, the stable value of pore water pressure shows a decreasing trend with the increase of shearing rate.
In clay shear deformation process, different shear rates have different effects on its structural damage, thus affecting its mechanical behavior. This paper takes the soft dredger fill from Tianjin Binhai New Area as research object. It discusses the structural about soft dredger fill, and carries out the triaxial shear tests to study effects on mechanical behavior caused by different shear rates, analyzes its mechanical effect of shearing rate. The test result indicates that as the shear rate increases, at low confining pressure condition, the strength and structural yield stress of soft dredger fill increase at first and then decrease, existing a critical shear rate. At high confining pressure condition, the strength and structural yield stress increase gradually, which shows a positive correlation with the shearing rate. The critical rate is disappearing gradually. However, at different confining pressure conditions, the cohesion of dredger fill decreases as the shearing rate increases. As the shearing rate increases, the internal friction angle shows an increasing trend at low confining pressure condition, which shows a decreasing trend at high confining pressure condition. In the shearing process, pore water pressure increases with the increase of axial strain to a certain value, and then becomes stable. With further increase of confining pressure, the stable value of pore water pressure shows a decreasing trend with the increase of shearing rate.
2015, 23(1): 13-20.
This paper is to prepare the similar material specimens with gradual variation of mechanical properties. The proportion tests is used to achieve the relationship between mechanical properties and proportion of cement-gypsum similar materials with different aggregates. A defined formula of proportion based on compressive strength and elastic modulus is determined via fitting the laboratory mechanical testing data of river-sand material. The test result shows that: water dosage, forming pressure and average particle diameter have effect of different levels and should be controlled in specimen preparation process. The tensile strength of low-intensity similar material is uncontrollable while the compressive strength and the elastic modulus show an obvious response to the change of proportion. For river sand similar material, the mechanical properties and the proportion present a linear relationship. While the standard sand similar material presents a nonlinear relationship between the mechanical properties and the proportion due to the critical content of cement and aggregate. The variable ranges of compressive strength and elastic modulus are 0～17.5MPa and 0.3～2.02GPa, respectively. The weathered rock can be simulated well using similar material in this range.
This paper is to prepare the similar material specimens with gradual variation of mechanical properties. The proportion tests is used to achieve the relationship between mechanical properties and proportion of cement-gypsum similar materials with different aggregates. A defined formula of proportion based on compressive strength and elastic modulus is determined via fitting the laboratory mechanical testing data of river-sand material. The test result shows that: water dosage, forming pressure and average particle diameter have effect of different levels and should be controlled in specimen preparation process. The tensile strength of low-intensity similar material is uncontrollable while the compressive strength and the elastic modulus show an obvious response to the change of proportion. For river sand similar material, the mechanical properties and the proportion present a linear relationship. While the standard sand similar material presents a nonlinear relationship between the mechanical properties and the proportion due to the critical content of cement and aggregate. The variable ranges of compressive strength and elastic modulus are 0～17.5MPa and 0.3～2.02GPa, respectively. The weathered rock can be simulated well using similar material in this range.
2015, 23(1): 21-29.
The deformation and shear strength parameters of soil-rock mixtures are mainly affected by the stone content, stone shape, nature of soil and water. Nowadays, the study mainly focuses on the three former aspects. The effect of water on the mechanical properties is rarely studied. This paper uses the pebbles, silty clay and water to make soil-rock mixture samples and carrys out large-scale direct shear tests. The test results show that as the shear displacement of model increases, the shear stress-displacement curve of soil-rock mixtures can be divided into three stages: linear deformation stage, initial yielding stage and hardening stage. The interaction of ratio of water and ratio of pebbles affects the mechanical properties of soil-rock mixtures. Overall, the shear strength of mixtures decreases as water content increases. The trend of decrease is slow at first, and then becomes rapid, and slow down again. For the same rock content, the internal frictional angle experiences two stages of decline process as the water content increases. Firstly, it decreases slowly when the water content is low. Then it decrease rapidly when the water content is high.
The deformation and shear strength parameters of soil-rock mixtures are mainly affected by the stone content, stone shape, nature of soil and water. Nowadays, the study mainly focuses on the three former aspects. The effect of water on the mechanical properties is rarely studied. This paper uses the pebbles, silty clay and water to make soil-rock mixture samples and carrys out large-scale direct shear tests. The test results show that as the shear displacement of model increases, the shear stress-displacement curve of soil-rock mixtures can be divided into three stages: linear deformation stage, initial yielding stage and hardening stage. The interaction of ratio of water and ratio of pebbles affects the mechanical properties of soil-rock mixtures. Overall, the shear strength of mixtures decreases as water content increases. The trend of decrease is slow at first, and then becomes rapid, and slow down again. For the same rock content, the internal frictional angle experiences two stages of decline process as the water content increases. Firstly, it decreases slowly when the water content is low. Then it decrease rapidly when the water content is high.
2015, 23(1): 30-36.
The large scale direct shear test system includes overlaying rings that are the important component of shear box. Multiple sets of shear surfaces can be formed according to the structure of coarse-grained soil, which can reflect shear deformation characteristics clearly. In order to analyze the influence of coarse granules composed of hard rock material on the strength and deformation, the large scale direct shear test is made on coarse-grained soil. The coarse grain lithology is granite. The paper analyzes experiment laws and particle motion of the hard rock coarse-grained soil and finds that granitic coarse grains have a significant impact on the strength and deformation. Because of their hard rock lithology, granitic particles are not easy to be broken. In fact they mainly do the position adjustment and rolling motion. Staircase of shear displacement emerges in shear zone under low axial stress. Nevertheless, shear displacement in shear zone manifestations linear variation and more apparent dilatancy effect under high axial stress. The coarse-grained soil has high shear strength and stability after shearing failure. The results provides certain reference for engineering construction.
The large scale direct shear test system includes overlaying rings that are the important component of shear box. Multiple sets of shear surfaces can be formed according to the structure of coarse-grained soil, which can reflect shear deformation characteristics clearly. In order to analyze the influence of coarse granules composed of hard rock material on the strength and deformation, the large scale direct shear test is made on coarse-grained soil. The coarse grain lithology is granite. The paper analyzes experiment laws and particle motion of the hard rock coarse-grained soil and finds that granitic coarse grains have a significant impact on the strength and deformation. Because of their hard rock lithology, granitic particles are not easy to be broken. In fact they mainly do the position adjustment and rolling motion. Staircase of shear displacement emerges in shear zone under low axial stress. Nevertheless, shear displacement in shear zone manifestations linear variation and more apparent dilatancy effect under high axial stress. The coarse-grained soil has high shear strength and stability after shearing failure. The results provides certain reference for engineering construction.
2015, 23(1): 37-43.
The water-saturated direct shear rock rheological test is carried out on the carbonaceous argillaceous limestone at the slip zone of Jiweishan landslide, Wulong, Chongqing. A rock direct shear rheometer is used. The rheological test results give the shear stress-shear displacement time-history curves of the slip zone and the long-term strength parameters of the rock. The results show that: the long-term strength in the water-saturated conditions significantly decreases, comparing to the rheological strength in the natural conditions and the instantaneous shear strength parameters. The internal frictional coefficient of the carbonaceous argillaceous limestone in the water-saturated conditions is lower than that of natural rheology 13.87%, and lower than that of the instantaneous shear 40.91%. The cohesion of the carbonaceous argillaceous limestone in the water-saturated conditions is lower than that of natural rheology 13.81%, and lower than that of the instantaneous shear 36.67%. Because of the crack damage propagation, the long-term shear strength in the water-saturated conditions decreases, comparing to that in the natural conditions, but does not decrease significantly, comparing to the long-term shear strength of the direct shear rheological test and the instantaneous shear strength. These findings can provide the important experimental and theoretical basis for in-depth understanding and analysis of the rheological mechanical properties of the slip zone soft rock in Jiweishan landslide.
The water-saturated direct shear rock rheological test is carried out on the carbonaceous argillaceous limestone at the slip zone of Jiweishan landslide, Wulong, Chongqing. A rock direct shear rheometer is used. The rheological test results give the shear stress-shear displacement time-history curves of the slip zone and the long-term strength parameters of the rock. The results show that: the long-term strength in the water-saturated conditions significantly decreases, comparing to the rheological strength in the natural conditions and the instantaneous shear strength parameters. The internal frictional coefficient of the carbonaceous argillaceous limestone in the water-saturated conditions is lower than that of natural rheology 13.87%, and lower than that of the instantaneous shear 40.91%. The cohesion of the carbonaceous argillaceous limestone in the water-saturated conditions is lower than that of natural rheology 13.81%, and lower than that of the instantaneous shear 36.67%. Because of the crack damage propagation, the long-term shear strength in the water-saturated conditions decreases, comparing to that in the natural conditions, but does not decrease significantly, comparing to the long-term shear strength of the direct shear rheological test and the instantaneous shear strength. These findings can provide the important experimental and theoretical basis for in-depth understanding and analysis of the rheological mechanical properties of the slip zone soft rock in Jiweishan landslide.
2015, 23(1): 44-51.
Inundating or humidifying process can easily destroy the distinct metastable structure of loess and control its mechanical behavior. This paper analyzes the microstructure of Malan loess at Zhaojiaan landslide area. It uses grain size analysis, scanning electron microscope, and mercury intrusion porosimetry. The results demonstrate that as the loess depth increases from surface to deep, the cementation of clay mineral is increasing gradually, the trellis pores is compressed obviously, and micro-pore is unchanged nearly. Triaxial compression test on loess with different initial water content shows that the strength of loess at top and bottom location decreases with increasing in water content. Since the loess at bottom location has higher clay cementation, its strength is larger than that at top. The cohesion strength parameter c is much more sensitive to water than the internal frictional angle . Therefore the strength reduction with depth is caused primarily by the decreasing of c. Water content increasing of loess at the bottom due to rising of ground water level can cause the parts of clay mineral to soften, undermine the cementation between particles, and continuously destruct the microstructure of loess, which resulted in wriggles of Zhaojiaan landslide.
Inundating or humidifying process can easily destroy the distinct metastable structure of loess and control its mechanical behavior. This paper analyzes the microstructure of Malan loess at Zhaojiaan landslide area. It uses grain size analysis, scanning electron microscope, and mercury intrusion porosimetry. The results demonstrate that as the loess depth increases from surface to deep, the cementation of clay mineral is increasing gradually, the trellis pores is compressed obviously, and micro-pore is unchanged nearly. Triaxial compression test on loess with different initial water content shows that the strength of loess at top and bottom location decreases with increasing in water content. Since the loess at bottom location has higher clay cementation, its strength is larger than that at top. The cohesion strength parameter c is much more sensitive to water than the internal frictional angle . Therefore the strength reduction with depth is caused primarily by the decreasing of c. Water content increasing of loess at the bottom due to rising of ground water level can cause the parts of clay mineral to soften, undermine the cementation between particles, and continuously destruct the microstructure of loess, which resulted in wriggles of Zhaojiaan landslide.
2015, 23(1): 52-58.
Hydropower station is generally associated with large scale, fast construction and unforeseen geological problems. Especially the deep anti-sliding stability problem is very important for the safe operation of hydropower project. For the above reasons, this paper takes Guanyinyan hydropower station on JinSha river as example. On the basis of one year work of tracing dam foundation excavation, we develop the observational based design method. The method including the following steps: the engineering geological conditions, the observational evaluation of weak intercalation characteristics, the observation based parameter values of weak intercalated structures, and the stability of the dam foundation. It takes the observational analysis of the weak intercalation distribution characteristics and its parameter as the core. The reasonable deep anti-sliding stability evaluation method is set up for dam foundation. The practice shows that the set of methods ensure the hydropower project construction period, and also provide reliable data for the stability evaluation.
Hydropower station is generally associated with large scale, fast construction and unforeseen geological problems. Especially the deep anti-sliding stability problem is very important for the safe operation of hydropower project. For the above reasons, this paper takes Guanyinyan hydropower station on JinSha river as example. On the basis of one year work of tracing dam foundation excavation, we develop the observational based design method. The method including the following steps: the engineering geological conditions, the observational evaluation of weak intercalation characteristics, the observation based parameter values of weak intercalated structures, and the stability of the dam foundation. It takes the observational analysis of the weak intercalation distribution characteristics and its parameter as the core. The reasonable deep anti-sliding stability evaluation method is set up for dam foundation. The practice shows that the set of methods ensure the hydropower project construction period, and also provide reliable data for the stability evaluation.
2015, 23(1): 65-71.
This paper investigates the qualitative and quantitative relationships among shear strength of weathered sand improved with expansive soil, weathered sand content and cycle times of freeze-thaw tests. The expansive soil is added with weathered sand with the percentages of 0, 10%, 20%, 30%, 40%, 50%,respectively. The shear strength test is done using direct shear apparatus on the samples after 0, 1, 3, 6, 9, 12 cycles of freezing and thawing. Test results show that as the cycles of freeze-thaw increases, the shear indexes and the shear strength of weathered sand improved expansive soil first increase and then decrease and gradually reach stable after several times of freeze-thaw cycles for samples with the same sand ratio. The relationship between cohesive force and freeze-thaw cycles can be expressed in logarithmic function. As the mixed sand ratio increases, the cohesion decrease but the internal frictional angle increases for samples with the same cycles of freeze and thaw.
This paper investigates the qualitative and quantitative relationships among shear strength of weathered sand improved with expansive soil, weathered sand content and cycle times of freeze-thaw tests. The expansive soil is added with weathered sand with the percentages of 0, 10%, 20%, 30%, 40%, 50%,respectively. The shear strength test is done using direct shear apparatus on the samples after 0, 1, 3, 6, 9, 12 cycles of freezing and thawing. Test results show that as the cycles of freeze-thaw increases, the shear indexes and the shear strength of weathered sand improved expansive soil first increase and then decrease and gradually reach stable after several times of freeze-thaw cycles for samples with the same sand ratio. The relationship between cohesive force and freeze-thaw cycles can be expressed in logarithmic function. As the mixed sand ratio increases, the cohesion decrease but the internal frictional angle increases for samples with the same cycles of freeze and thaw.
2015, 23(1): 72-77.
This paper carries the moisture migration tests of unsaturated loess with the large size sample under freezing effect. It examines the influence of density, water content, freezing temperatures and freezing way on moisture migration of unsaturated loess. Results show that the soil sample temperature change under freezing process is divided into three stages: rapid cooling stage, the slow cooling stage, and stable stage. For higher dry density, the increase of water content at the frozen front is greater, but the increase of water migration of moving to the frozen part is lower. For a certain dry density, if the initial water content is higher, the amount of moisture migration is greater. And the increase of water content of the frozen front is also the greater. From the cold end to the warm end in the unfrozen area, water content increases at first, then decreases. And, this phenomenon is the more evident with lower initial water content. This phenomenon is the combined effect of the freezing interface suction force, temperature gradient and the matric suction gradient. The water content distribution and the total amount of moisture migration in frozen area are affected directly by the freezing way.
This paper carries the moisture migration tests of unsaturated loess with the large size sample under freezing effect. It examines the influence of density, water content, freezing temperatures and freezing way on moisture migration of unsaturated loess. Results show that the soil sample temperature change under freezing process is divided into three stages: rapid cooling stage, the slow cooling stage, and stable stage. For higher dry density, the increase of water content at the frozen front is greater, but the increase of water migration of moving to the frozen part is lower. For a certain dry density, if the initial water content is higher, the amount of moisture migration is greater. And the increase of water content of the frozen front is also the greater. From the cold end to the warm end in the unfrozen area, water content increases at first, then decreases. And, this phenomenon is the more evident with lower initial water content. This phenomenon is the combined effect of the freezing interface suction force, temperature gradient and the matric suction gradient. The water content distribution and the total amount of moisture migration in frozen area are affected directly by the freezing way.
2015, 23(1): 78-85.
2008 Wenchuan earthquake triggered more than 300 large landslides followed by huge loss of life and property, which emphasizes that study on their forming mechanism has a great significance in theory and practical application for disaster prevention and mitigation. By field investigation and analysis on published material about the landslides, a new term landslide-quake is defined in this paper. It is different from Whenchuan mainshock by its effect on the forming of the landslides. This paper looks into the evidences, formations and characteristics of landslide-quake. It gives different combinations of landslide-quake and earthquake. It finds that these large landslides triggered by 2008 Wenchuan earthquake can be classified into the following three types.(1)Normal earthquake landslide, for which no landslide-quake occurs and the main contributing forces are earthquake force and the gravity of sliding mass.(2)During earthquake landslide, for which a landslide-quake generates during the earthquake and the main contributing forces are landslide-quake force, earthquake force and the gravity of sliding mass.(3)After-earthquake landslide, for which a landslide-quake generates after the earthquake and the main contributing forces are landslide-quake force and the gravity of sliding mass. The opinion is suggested that the process of large landslide generation is similar to the sudden cut of a seismic fault and the estimation of the magnitude of a landslide-quake and the provided shearing force. Based on the above, the processes of the sudden initiations of these three kinds of landslides are analyzed. The concept of landslide-quake is a new explanation for the mechanism of sudden initiation of a large rapid landslide, and it, along with the other results of this study, provides a reference for large rapid landslide research.
2008 Wenchuan earthquake triggered more than 300 large landslides followed by huge loss of life and property, which emphasizes that study on their forming mechanism has a great significance in theory and practical application for disaster prevention and mitigation. By field investigation and analysis on published material about the landslides, a new term landslide-quake is defined in this paper. It is different from Whenchuan mainshock by its effect on the forming of the landslides. This paper looks into the evidences, formations and characteristics of landslide-quake. It gives different combinations of landslide-quake and earthquake. It finds that these large landslides triggered by 2008 Wenchuan earthquake can be classified into the following three types.(1)Normal earthquake landslide, for which no landslide-quake occurs and the main contributing forces are earthquake force and the gravity of sliding mass.(2)During earthquake landslide, for which a landslide-quake generates during the earthquake and the main contributing forces are landslide-quake force, earthquake force and the gravity of sliding mass.(3)After-earthquake landslide, for which a landslide-quake generates after the earthquake and the main contributing forces are landslide-quake force and the gravity of sliding mass. The opinion is suggested that the process of large landslide generation is similar to the sudden cut of a seismic fault and the estimation of the magnitude of a landslide-quake and the provided shearing force. Based on the above, the processes of the sudden initiations of these three kinds of landslides are analyzed. The concept of landslide-quake is a new explanation for the mechanism of sudden initiation of a large rapid landslide, and it, along with the other results of this study, provides a reference for large rapid landslide research.
2015, 23(1): 86-92.
Tower rock has a kind of common potential geohazard in limestone mountainous area of southwest China. This type of rocks is widely distributed and prone to be damaged. Their collapse can be induced by many factors. Taking Zengziyan perilous rock as example, this paper presents a detailed analysis of the process of tower rock collapse. The analyses of the collapse and especially for its motion characteristic are based on video data. The process of Zengziyan perilous rock collapse can be divided into three motion phases: startup phase, acceleration phase and collision phase. The failure begins at the bottom of tower rock. During the falling process, some features such as cracks propagation and damage transfer from the bottom up are taking place. The acceleration curve of Zengziyan tower rock shows a continuous negative fluctuation similar to buffering in declining stage. And motion characteristic curves of different monitoring locations have significant differences with time, which indicates that there are rupture, collision and disintegration synchronously when the tower rock falling.
Tower rock has a kind of common potential geohazard in limestone mountainous area of southwest China. This type of rocks is widely distributed and prone to be damaged. Their collapse can be induced by many factors. Taking Zengziyan perilous rock as example, this paper presents a detailed analysis of the process of tower rock collapse. The analyses of the collapse and especially for its motion characteristic are based on video data. The process of Zengziyan perilous rock collapse can be divided into three motion phases: startup phase, acceleration phase and collision phase. The failure begins at the bottom of tower rock. During the falling process, some features such as cracks propagation and damage transfer from the bottom up are taking place. The acceleration curve of Zengziyan tower rock shows a continuous negative fluctuation similar to buffering in declining stage. And motion characteristic curves of different monitoring locations have significant differences with time, which indicates that there are rupture, collision and disintegration synchronously when the tower rock falling.
2015, 23(1): 93-104.
The Newmark displacement model is preliminarily used for quantitative seismic landslide hazard assessment in Chinese mainland. In order to distinguish concepts and promote the application of this mechanical model based assessment method, we firstly analyze the correlation of the narrow sense seismic landslide hazard forecast assessment and post-earthquake inversion assessment. In order to meet different landslide assessing requirements under earthquake emergency response, post-earthquake reconstruction and potential earthquake conditions, we preliminarily develop a generalized seismic landslide hazard assessment framework. Then, we review the theoretical foundation, basic assumptions, method classification and their applicability of seismic landslide hazard assessment method in association with Newmark model. Also, the latest progress of regional assessment method using simplified displacement is reviewed. Taking the rapid assessment for Wenchuan earthquake inducing landslide hazard as an example, we analyze uncertainties and spatial data problem which affect the effectiveness of assessment. We suggest the improvements to the mechanical model based seismic landslide hazard assessment. It should be noted that the coupled hazard assessment of potential earthquake and the inducing landslide needs to be carried out. Empirical seismic landslide displacement analyzing model applicable to Chinese mainland needs to be developed, so as to promote national seismic landslide hazard zoning.
The Newmark displacement model is preliminarily used for quantitative seismic landslide hazard assessment in Chinese mainland. In order to distinguish concepts and promote the application of this mechanical model based assessment method, we firstly analyze the correlation of the narrow sense seismic landslide hazard forecast assessment and post-earthquake inversion assessment. In order to meet different landslide assessing requirements under earthquake emergency response, post-earthquake reconstruction and potential earthquake conditions, we preliminarily develop a generalized seismic landslide hazard assessment framework. Then, we review the theoretical foundation, basic assumptions, method classification and their applicability of seismic landslide hazard assessment method in association with Newmark model. Also, the latest progress of regional assessment method using simplified displacement is reviewed. Taking the rapid assessment for Wenchuan earthquake inducing landslide hazard as an example, we analyze uncertainties and spatial data problem which affect the effectiveness of assessment. We suggest the improvements to the mechanical model based seismic landslide hazard assessment. It should be noted that the coupled hazard assessment of potential earthquake and the inducing landslide needs to be carried out. Empirical seismic landslide displacement analyzing model applicable to Chinese mainland needs to be developed, so as to promote national seismic landslide hazard zoning.
2015, 23(1): 105-110.
Accompanying with the rapid economic growth and urbanization expansion of the coastal areas of Tangshan, the quantity of groundwater exploitation has increased and land subsidence has aggravated. We analyze the hydrogeology condition in this region, and generalizes it into six compressed layers including three aquifers and three aquitards. A fully coupling model of three-dimensional groundwater flow and vertical one-dimensional compression is constructed. The simulation data, derived from the model calibrated with a 25 years observational data, are fitted well with the measured values, which verifies the model validity. According to our prediction, subsidence amount in subsidence center will be accumulatively up to 1192.3mm after 10 years. The subsidence over ten years will reach 352.3mm and the average subsidence rate will attain to 35.23mma-1 under present groundwater exploitation. If the amount of groundwater extraction increases 10%on the basis of existing mining quantity, the subsidence amount in subsidence center will achieve 1260.8mm. The subsidence amount in ten years will grow up to 420.8mm and the average subsidence rate will be 42.08mma-1.If reducing the groundwater extraction in 10%based on the existing mining quantity, at subsidence center the subsidence amount will accumulate to 1088.7mm. Subsidence amount in ten years will reach 247.9mm and the average subsidence rate will be 24.79mma-1. Subsidence amount over ten years will increase 68.5mm if the groundwater exploitation extends 10%, and it will decrease 104.4mm if the groundwater extraction reduces 10%.In summary, limiting the groundwater withdrawal is an effective method to control the land subsidence.
Accompanying with the rapid economic growth and urbanization expansion of the coastal areas of Tangshan, the quantity of groundwater exploitation has increased and land subsidence has aggravated. We analyze the hydrogeology condition in this region, and generalizes it into six compressed layers including three aquifers and three aquitards. A fully coupling model of three-dimensional groundwater flow and vertical one-dimensional compression is constructed. The simulation data, derived from the model calibrated with a 25 years observational data, are fitted well with the measured values, which verifies the model validity. According to our prediction, subsidence amount in subsidence center will be accumulatively up to 1192.3mm after 10 years. The subsidence over ten years will reach 352.3mm and the average subsidence rate will attain to 35.23mma-1 under present groundwater exploitation. If the amount of groundwater extraction increases 10%on the basis of existing mining quantity, the subsidence amount in subsidence center will achieve 1260.8mm. The subsidence amount in ten years will grow up to 420.8mm and the average subsidence rate will be 42.08mma-1.If reducing the groundwater extraction in 10%based on the existing mining quantity, at subsidence center the subsidence amount will accumulate to 1088.7mm. Subsidence amount in ten years will reach 247.9mm and the average subsidence rate will be 24.79mma-1. Subsidence amount over ten years will increase 68.5mm if the groundwater exploitation extends 10%, and it will decrease 104.4mm if the groundwater extraction reduces 10%.In summary, limiting the groundwater withdrawal is an effective method to control the land subsidence.
2015, 23(1): 111-118.
Debris flows can occur abruptly and rapidly in mountainous areas. It is difficult to observe their occurrence process. Therefore, field experiment becomes an important method to study debris flow initiation mechanism in recent years. This paper takes Xiongjia gully as an example and uses artificial rainfall experiment to study initiation of groove-type debris flow. Experimental results indicate some relations among rainfall intensity and gully erosion, slope stability and failure mode, debris flow initiation mechanism and characteristics. Conclusions are drawn as follows:(1)Under strong precipitation, infiltration rate and soil water content at different depths are inversely proportional with rainfall intensity. Intense rainfall favors overland flow, gully runoff and erosion, but is not conducive to water infiltration. (2)Slope failure modes and debris flow initiation mechanism are various under different rainfall and runoff conditions. Under the condition with rainfall intensity of 55mmh-1, the slope failure mode presents soil liquefaction and landslide. Accordingly, debris flow initiation mechanism belongs to landslide conversion. However, under the condition of intense rainfall and runoff, gully beds are easily to be eroded and slopes are prone to collapse. Then, debris flows occurred with initiation mechanism of entrainment. (3)In terms of debris flow characteristics, debris flow occurrence process consists of several intermittent flows. In addition, debris flow magnitude and flow viscosity are not consistent with rainfall intensity. On the contrary, under condition of intense rainfall of 65mmh-1 and 75mmh-1,debris flows tend to be watery. But with rainfall condition of 55mmh-1, the flow viscosity is higher. The experimental results are well consistent with the natural debris flow occurrence at Xioangjia gully.
Debris flows can occur abruptly and rapidly in mountainous areas. It is difficult to observe their occurrence process. Therefore, field experiment becomes an important method to study debris flow initiation mechanism in recent years. This paper takes Xiongjia gully as an example and uses artificial rainfall experiment to study initiation of groove-type debris flow. Experimental results indicate some relations among rainfall intensity and gully erosion, slope stability and failure mode, debris flow initiation mechanism and characteristics. Conclusions are drawn as follows:(1)Under strong precipitation, infiltration rate and soil water content at different depths are inversely proportional with rainfall intensity. Intense rainfall favors overland flow, gully runoff and erosion, but is not conducive to water infiltration. (2)Slope failure modes and debris flow initiation mechanism are various under different rainfall and runoff conditions. Under the condition with rainfall intensity of 55mmh-1, the slope failure mode presents soil liquefaction and landslide. Accordingly, debris flow initiation mechanism belongs to landslide conversion. However, under the condition of intense rainfall and runoff, gully beds are easily to be eroded and slopes are prone to collapse. Then, debris flows occurred with initiation mechanism of entrainment. (3)In terms of debris flow characteristics, debris flow occurrence process consists of several intermittent flows. In addition, debris flow magnitude and flow viscosity are not consistent with rainfall intensity. On the contrary, under condition of intense rainfall of 65mmh-1 and 75mmh-1,debris flows tend to be watery. But with rainfall condition of 55mmh-1, the flow viscosity is higher. The experimental results are well consistent with the natural debris flow occurrence at Xioangjia gully.
2015, 23(1): 119-125.
Beidou Navigation Satellite System(BDS) of China has formally provided the service of continuous passive positioning, navigation and timing for most area of Asia-Pacific since December 27, 2012. In order to inquire the effect and precision of the high precision land subsidence monitoring using fused BDS/GPS observation data, five GNSS receivers which can synchronous receive the signal of BDS and GPS are used to monitor the land subsidence of Xi'an repeatedly at 9 points of the original GPS network. Then 4 session observation data which continue over 10 hours are processed and analyzed. The results indicate that the internal accordant accuracy of baseline which merges the BDS and GPS data is improved greatly relative to the accuracy of baseline solved using the single GPS observation data. The average error of horizontal direction is improved from 5mm to 3mm, and the average error of vertical direction is improved from 17mm to 12mm. In the mean time, the external accordant accuracy of monitor results is also enhanced greatly. The average error of X,Y,Z direction is improved from 6mm,15mm and 10mm to1.5mm,8mm and 5mm respectively. Those phenomena indicate that the internal and external accordant accuracy of results for high precision land subsidence monitoring can be improved obviously using the fused BDS/GPS observation data.
Beidou Navigation Satellite System(BDS) of China has formally provided the service of continuous passive positioning, navigation and timing for most area of Asia-Pacific since December 27, 2012. In order to inquire the effect and precision of the high precision land subsidence monitoring using fused BDS/GPS observation data, five GNSS receivers which can synchronous receive the signal of BDS and GPS are used to monitor the land subsidence of Xi'an repeatedly at 9 points of the original GPS network. Then 4 session observation data which continue over 10 hours are processed and analyzed. The results indicate that the internal accordant accuracy of baseline which merges the BDS and GPS data is improved greatly relative to the accuracy of baseline solved using the single GPS observation data. The average error of horizontal direction is improved from 5mm to 3mm, and the average error of vertical direction is improved from 17mm to 12mm. In the mean time, the external accordant accuracy of monitor results is also enhanced greatly. The average error of X,Y,Z direction is improved from 6mm,15mm and 10mm to1.5mm,8mm and 5mm respectively. Those phenomena indicate that the internal and external accordant accuracy of results for high precision land subsidence monitoring can be improved obviously using the fused BDS/GPS observation data.
2015, 23(1): 126-134.
The karst collapse is one of the main environmental geological problems, which affects and restricts the social and economic development in karst area. Through monitoring, the changing process of karst caves can be observed. It includes extent, location and stress. Further, the monitoring data can provide data support for prediction of karst collapse and avoiding disaster. This paper systematically introduces the main monitoring work according to the problem of karst collapse. In order to systematically provide the references of karst collapse monitoring techniques and methods, and to provide basic support for mechanism research of karst collapse, we propose the monitoring contents and corresponding monitoring techniques, methods and means. In the end, it is pointed out that the focus of monitoring for karst collapse in the future is to combine the advanced and traditional monitoring techniques together.
The karst collapse is one of the main environmental geological problems, which affects and restricts the social and economic development in karst area. Through monitoring, the changing process of karst caves can be observed. It includes extent, location and stress. Further, the monitoring data can provide data support for prediction of karst collapse and avoiding disaster. This paper systematically introduces the main monitoring work according to the problem of karst collapse. In order to systematically provide the references of karst collapse monitoring techniques and methods, and to provide basic support for mechanism research of karst collapse, we propose the monitoring contents and corresponding monitoring techniques, methods and means. In the end, it is pointed out that the focus of monitoring for karst collapse in the future is to combine the advanced and traditional monitoring techniques together.
2015, 23(1): 135-139.
Strength parameters of slope rock and soil can have spatial variability. Unified strength parameters for numerical modelling of slope stability can't reflect the effect of this nature in the calculation results. A new method of numerical simulation for slope stability is proposed in this paper. It takes into account the spatial variable distribution of the strength parameters in the slope. Using the topography and survey data, the spatial variation of the strength parameters can be reformed into a cloud contour map. With the help of Visual Basic programming and FISH language, the contour data of strength parameters are added to the numerical simulation model. Simulation results show that the method is workable and is more accurate in indicating the deforming location and situation, with has a guiding significance on landslide deformation monitoring and treatment.
Strength parameters of slope rock and soil can have spatial variability. Unified strength parameters for numerical modelling of slope stability can't reflect the effect of this nature in the calculation results. A new method of numerical simulation for slope stability is proposed in this paper. It takes into account the spatial variable distribution of the strength parameters in the slope. Using the topography and survey data, the spatial variation of the strength parameters can be reformed into a cloud contour map. With the help of Visual Basic programming and FISH language, the contour data of strength parameters are added to the numerical simulation model. Simulation results show that the method is workable and is more accurate in indicating the deforming location and situation, with has a guiding significance on landslide deformation monitoring and treatment.
2015, 23(1): 140-147.
Early warning system acts as an important role in improving the actively responding ability of human beings to control and mitigate geohazards. Especially, geohazards have occurred more and more frequently in recent years with the construction and resource exploitation in the Southwest of China. By the restriction of economic development and so on, however, only a part of geohazards have been controlled through engineering construction. Others need to be prevented with effective monitoring. This paper begins with some key points in order to establish early geohazards warning system. Then, it summarizes the main characteristics of modern information technology, and puts forward the data collection, remote wireless transmission, data organization and integration, and fast data mining method. They are base on Internet of Things, modern mobile communication and cloud computing technologies. Meanwhile, a real-time early geohazard warning system has been developed. The Longjingwan landslide is selected for example application. The results show that the methods are feasible. The system functionalities are reliability basically. They can provide a useful technology support for geohazards mitigating and preventing.
Early warning system acts as an important role in improving the actively responding ability of human beings to control and mitigate geohazards. Especially, geohazards have occurred more and more frequently in recent years with the construction and resource exploitation in the Southwest of China. By the restriction of economic development and so on, however, only a part of geohazards have been controlled through engineering construction. Others need to be prevented with effective monitoring. This paper begins with some key points in order to establish early geohazards warning system. Then, it summarizes the main characteristics of modern information technology, and puts forward the data collection, remote wireless transmission, data organization and integration, and fast data mining method. They are base on Internet of Things, modern mobile communication and cloud computing technologies. Meanwhile, a real-time early geohazard warning system has been developed. The Longjingwan landslide is selected for example application. The results show that the methods are feasible. The system functionalities are reliability basically. They can provide a useful technology support for geohazards mitigating and preventing.
2015, 23(1): 148-154.
The safety of underground salt cavity gas storage is the key geological problem of gas storage operation. The Pingdingshan salt field is characterized with thin layers, multiple interlayers and deeply buried layers. Its geological storage feasibility and ground settlement are studied using the permeability, rheology and stability of layered salt rock. First, the pure salt rock, layered salt rock and mudstone interlayer samples are collected. Then electronic microscope scanning and triaxial compression creep experiments are conducted. Then the salt rock cavities are detected by CYT method. Field monitoring shows that ground settlement is small and fluctuating because some influence zones of mining wells are overlapped. Based on the geological characteristics of study area, it can be concluded that the geological conditions of Pingdingshan underground salt cavity gas storage are favorable, and also can provide some references for similar projects in China.
The safety of underground salt cavity gas storage is the key geological problem of gas storage operation. The Pingdingshan salt field is characterized with thin layers, multiple interlayers and deeply buried layers. Its geological storage feasibility and ground settlement are studied using the permeability, rheology and stability of layered salt rock. First, the pure salt rock, layered salt rock and mudstone interlayer samples are collected. Then electronic microscope scanning and triaxial compression creep experiments are conducted. Then the salt rock cavities are detected by CYT method. Field monitoring shows that ground settlement is small and fluctuating because some influence zones of mining wells are overlapped. Based on the geological characteristics of study area, it can be concluded that the geological conditions of Pingdingshan underground salt cavity gas storage are favorable, and also can provide some references for similar projects in China.
2015, 23(1): 155-160.
The Nanjing Deji Plaza(Phase 2)project is located at the center of Nanjing. Excavation depths of main building and attached building are 21.50m and 19.70m respectively. The excavation depth of the foundation pit is deep. The pit area is huge. This paper analyzes the project structure, engineering geological conditions, hydrogeology conditions, surrounding environment and especially protection of subway tunnel. Pit support structure adopts underground diaphragm wall with two walls joining together. The attached building is constructed with top-down method. The main building is constructed with down-top method. This paper has put forward the protection measures to subway tunnel. In addition, this paper uses the general finite element analysis software to calculate the influence to subway tunnel by foundation pit excavation. The results show that this project has little impact on surrounding environment using top-down method, and meets the requirement of tunnel deformation with metro operation. This paper has a certain guiding significance for the projects with top-down method.
The Nanjing Deji Plaza(Phase 2)project is located at the center of Nanjing. Excavation depths of main building and attached building are 21.50m and 19.70m respectively. The excavation depth of the foundation pit is deep. The pit area is huge. This paper analyzes the project structure, engineering geological conditions, hydrogeology conditions, surrounding environment and especially protection of subway tunnel. Pit support structure adopts underground diaphragm wall with two walls joining together. The attached building is constructed with top-down method. The main building is constructed with down-top method. This paper has put forward the protection measures to subway tunnel. In addition, this paper uses the general finite element analysis software to calculate the influence to subway tunnel by foundation pit excavation. The results show that this project has little impact on surrounding environment using top-down method, and meets the requirement of tunnel deformation with metro operation. This paper has a certain guiding significance for the projects with top-down method.
2015, 23(1): 161-169.
In essence, how much the engineering safety distance to active fault belongs the fracture-resistance problem. Aim is to reduce damage to the building due to occurrence of the active fault rupture in the future. Not all active faults can produce surface rupture. The seismo-active fault is the object of engineering avoidance. Researchers suggest many engineering distances to active fault using different methods. Whether these distances are suitable for a particular active fault still needs to conduct specialized research about this active fault. This paper respectively uses Helan Mountain piedmont fault and Yinchuan buried fault for an example. It studies the tectonic history of the active faults using the basic research method for active faults. It uses the past to predict the future of the active fault. The results of this study provide the basis for the active fault avoidance. To the exposed active fault, the first work is to identify whether it is a seismo-active fault using geological mapping, trenching. Then it is to determine the location of the engineering active fault avoidance according to recurrence characteristics of paleoearthquake events and fault scarp landscape in situ. The width of the fault zone in trench and the width of fault scarps can be used as a reference engineering safe distance from the active fault. For buried active faults, the location of the fault should first be positioned through various means. The results of trenching and drilling are to identify capable active faults and to analyze the tectonic activity history of the fault. The situ recurrence characteristics of the paleoearthquake events and the fault throw changes of different sedimentary strata at different depths in drilling profiles can be used to predict the future location of surface rupture. Location of the fault plane extended at the surface can be the occurrence location of the next earthquake surface rupture. It is the reference point to engineering safe distance. Through analysis, the distance of 15m that was given by previous researchers from statistics can be applied to Helan Mountain piedmont fault and Yinchuan buried fault. The engineering safety distance to Yinchuan buried active fault is 40m if the maximum positioning error is taken into account.
In essence, how much the engineering safety distance to active fault belongs the fracture-resistance problem. Aim is to reduce damage to the building due to occurrence of the active fault rupture in the future. Not all active faults can produce surface rupture. The seismo-active fault is the object of engineering avoidance. Researchers suggest many engineering distances to active fault using different methods. Whether these distances are suitable for a particular active fault still needs to conduct specialized research about this active fault. This paper respectively uses Helan Mountain piedmont fault and Yinchuan buried fault for an example. It studies the tectonic history of the active faults using the basic research method for active faults. It uses the past to predict the future of the active fault. The results of this study provide the basis for the active fault avoidance. To the exposed active fault, the first work is to identify whether it is a seismo-active fault using geological mapping, trenching. Then it is to determine the location of the engineering active fault avoidance according to recurrence characteristics of paleoearthquake events and fault scarp landscape in situ. The width of the fault zone in trench and the width of fault scarps can be used as a reference engineering safe distance from the active fault. For buried active faults, the location of the fault should first be positioned through various means. The results of trenching and drilling are to identify capable active faults and to analyze the tectonic activity history of the fault. The situ recurrence characteristics of the paleoearthquake events and the fault throw changes of different sedimentary strata at different depths in drilling profiles can be used to predict the future location of surface rupture. Location of the fault plane extended at the surface can be the occurrence location of the next earthquake surface rupture. It is the reference point to engineering safe distance. Through analysis, the distance of 15m that was given by previous researchers from statistics can be applied to Helan Mountain piedmont fault and Yinchuan buried fault. The engineering safety distance to Yinchuan buried active fault is 40m if the maximum positioning error is taken into account.
2015, 23(1): 170-177.
This paper uses the measured high density resistivity data to build 3-D data field. It chooses the 3-D inversion technique in association with the least squares method to process the data field after inversion parameter optimization. The inversion results are presented using 3-D visualization imaging technology. The results show that the use of 3-D processing technology can analyze the geophysical data spatially through multi-tool and multi-angle and can effectively eliminate the influence of the side effects. Geophysical results are more intuitive, clear and easy for analysis and interpretation. Finally, using drilling information, the accuracy and advancement of 3-D data processing technology are proved.
This paper uses the measured high density resistivity data to build 3-D data field. It chooses the 3-D inversion technique in association with the least squares method to process the data field after inversion parameter optimization. The inversion results are presented using 3-D visualization imaging technology. The results show that the use of 3-D processing technology can analyze the geophysical data spatially through multi-tool and multi-angle and can effectively eliminate the influence of the side effects. Geophysical results are more intuitive, clear and easy for analysis and interpretation. Finally, using drilling information, the accuracy and advancement of 3-D data processing technology are proved.
2015, 23(1): 178-185.
The reinforcing and restraining effect of piles embedded in soils is objective. However, this effect is not or has not been effectively considered in the present theory. The relevant research work needs to be continued. Based on the shear displacement method, the reinforcing and restraining effect is taken into account in the calculation of the pile group settlements in this paper. The reduction effect caused by the existence of the other adjacent piles and the equivalent stiffness coefficients of soil around each pile are developed. Then on the basis of the shear deformation transfer method, vertical displacement equation caused by load acting on top of the analyzing pile is built. So recurrence relations of settlement and axial force between pile head and pile tip are respectively deduced. Thus a flexibility coefficient of the displacement at the pile top induced by its load is obtained. Meanwhile, the flexibility coefficients for the piles due to the loads of adjacent piles are also gained. Lastly, a flexibility coefficient matrix equation is built to calculate settlement of pile groups with high or low pile caps. On the process of the deducing, the multilayer of soils and the interaction of settlements between piles bases are taken into consideration. A new relationship between pile-end resistance and pile-end settlement is proposed using Mindlin displacement solution. Comparisons of the settlement calculation for two pile cases are given to demonstrate the effectiveness and accuracy of the proposed method. The calculating interaction coefficients are much less than the elastic theory methods.
The reinforcing and restraining effect of piles embedded in soils is objective. However, this effect is not or has not been effectively considered in the present theory. The relevant research work needs to be continued. Based on the shear displacement method, the reinforcing and restraining effect is taken into account in the calculation of the pile group settlements in this paper. The reduction effect caused by the existence of the other adjacent piles and the equivalent stiffness coefficients of soil around each pile are developed. Then on the basis of the shear deformation transfer method, vertical displacement equation caused by load acting on top of the analyzing pile is built. So recurrence relations of settlement and axial force between pile head and pile tip are respectively deduced. Thus a flexibility coefficient of the displacement at the pile top induced by its load is obtained. Meanwhile, the flexibility coefficients for the piles due to the loads of adjacent piles are also gained. Lastly, a flexibility coefficient matrix equation is built to calculate settlement of pile groups with high or low pile caps. On the process of the deducing, the multilayer of soils and the interaction of settlements between piles bases are taken into consideration. A new relationship between pile-end resistance and pile-end settlement is proposed using Mindlin displacement solution. Comparisons of the settlement calculation for two pile cases are given to demonstrate the effectiveness and accuracy of the proposed method. The calculating interaction coefficients are much less than the elastic theory methods.
微信 | 公众平台 
