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Editor Work2015 Vol. 23, No. 6
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2015, 23(6): 1039-1044.
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This paper aims to examine the effect of water-rock interaction on mechanical property of altered rock. Rock samples from the slope are selected. Rock mechanics testing is carried out to examine the effect of different saturation-dehydration frequencies. The function is established to describe the variation pattern of mechanical properties of altered rock with the circulating effect. The influence of mechanical properties of altered rock with different circulating times is analyzed, using the concept of damage rate. The project result indicates that the mechanical properties of the altered rocks are obviously weakened by water-rock interaction. With the increase of water-rock interaction, the phenomenon is more obvious. With different circulating times, the tensile strength and the modulus of elasticity decay rapidly while the peak intensity is decaying continuously. When the degree of alteration of all rock has no difference, the degree of deterioration of tensile strength is the biggest, followed by the modulus of elasticity and minimum uniaxial compressive strength. As the degree of alteration and fragmentation increases, the degree of damage increases regarding the water-rock interaction to the mechanical properties of rock. The damage rate of tensile strength can reach 63%,the modulus of elasticity can reach 60%,as the present of peak intensity is 48%.And with the increase of saturation-dehydration circulation, the deterioration phenomenon of altered rocks is stable.
This paper aims to examine the effect of water-rock interaction on mechanical property of altered rock. Rock samples from the slope are selected. Rock mechanics testing is carried out to examine the effect of different saturation-dehydration frequencies. The function is established to describe the variation pattern of mechanical properties of altered rock with the circulating effect. The influence of mechanical properties of altered rock with different circulating times is analyzed, using the concept of damage rate. The project result indicates that the mechanical properties of the altered rocks are obviously weakened by water-rock interaction. With the increase of water-rock interaction, the phenomenon is more obvious. With different circulating times, the tensile strength and the modulus of elasticity decay rapidly while the peak intensity is decaying continuously. When the degree of alteration of all rock has no difference, the degree of deterioration of tensile strength is the biggest, followed by the modulus of elasticity and minimum uniaxial compressive strength. As the degree of alteration and fragmentation increases, the degree of damage increases regarding the water-rock interaction to the mechanical properties of rock. The damage rate of tensile strength can reach 63%,the modulus of elasticity can reach 60%,as the present of peak intensity is 48%.And with the increase of saturation-dehydration circulation, the deterioration phenomenon of altered rocks is stable.
2015, 23(6): 1045-1052.
The region of Zhouqu and Wudu in Gansu province is one of the most intensive activities and the most frequent areas of geological disasters such as landslide and debris flow. The process of the water-rock interaction of the wide outcrop of Silurian slate in the area is one of the main reasons that the landslides and debris flow can highly develop. The paper observes the macro morphology and tests the variation of qualities in elastic wave velocity and uniaxial compressive strength of the slate samples after saturated cycles and wet and dry cycles in different times. It compares the process of crack propagations and the variations of quality, strength and such related indicators of slate sample under two kinds of water-rock interactions. The test results reveal the degradation law of slate under water-rock interaction. Preliminary discussions are given on the mechanism of degradation of slate under different water-rock interactions. The study provides a useful reference for evaluation and prevention of landslide and debris flow disasters.
The region of Zhouqu and Wudu in Gansu province is one of the most intensive activities and the most frequent areas of geological disasters such as landslide and debris flow. The process of the water-rock interaction of the wide outcrop of Silurian slate in the area is one of the main reasons that the landslides and debris flow can highly develop. The paper observes the macro morphology and tests the variation of qualities in elastic wave velocity and uniaxial compressive strength of the slate samples after saturated cycles and wet and dry cycles in different times. It compares the process of crack propagations and the variations of quality, strength and such related indicators of slate sample under two kinds of water-rock interactions. The test results reveal the degradation law of slate under water-rock interaction. Preliminary discussions are given on the mechanism of degradation of slate under different water-rock interactions. The study provides a useful reference for evaluation and prevention of landslide and debris flow disasters.
2015, 23(6): 1053-1058.
Swelling deformation tests of a commercial bentonite are performed in distilled water and NaCl solution with different concentrations. The results show the swelling characteristics decrease with the increase of solution concentration. Study on the results finds that the greater concentration of inundation solution exerts greater osmotic suction . Increase in osmotic suction apparently acts as an equivalent effective stress that favors a reduction in swell potential of the compacted bentonite specimens. It means that, the effective stress includes the part of applied loads p and the part of osmotic suction p. The relationship between montmorillonite void ratio em and effective stress pe can be represented by a unified curve for bentonite in salt solution with different concentration and distilled water, and the part of osmotic suction p=(p/)0.66.
Swelling deformation tests of a commercial bentonite are performed in distilled water and NaCl solution with different concentrations. The results show the swelling characteristics decrease with the increase of solution concentration. Study on the results finds that the greater concentration of inundation solution exerts greater osmotic suction . Increase in osmotic suction apparently acts as an equivalent effective stress that favors a reduction in swell potential of the compacted bentonite specimens. It means that, the effective stress includes the part of applied loads p and the part of osmotic suction p. The relationship between montmorillonite void ratio em and effective stress pe can be represented by a unified curve for bentonite in salt solution with different concentration and distilled water, and the part of osmotic suction p=(p/)0.66.
2015, 23(6): 1059-1065.
This paper investigates coal strength and damage charateristics under bidirectional loading, obtains the mechanical parameters by testing the coal under uniaxial compression, then gets coal mesomechanical parameters through particle flow code(PFC) and fish program combined with the uniaxial experimental results. It conducts the research on coal strength, deformation and acoustic emission under biaxial loading. The main research results are reached as follows. In coal deformation and failure process under bidirectional loading, intermediate principal stress has the most significant effect on the yield stage, but no effects on the post-peak softening stage, which is different from the effects confining compression on the post-peak softening stage under triaxial loading. This result shows that coal under biaxial loading basically does not have the features of brittle converting ductile in post-peak stage. Coal volumetric strain under biaxial loading shows the three stages of linear volumetric strain decrease, nonlinear expansion and linear expansion. Intermediate principal stress has the most significant effects on nonlinear expansion stage, but no effects on other two stages. In coal damage and failure process, acoustic emission linearly increases at elastic stage, but the growth rate is smaller, nonlinearly rapidly increases at yield stage. It has the fastest growing near peak, reaches the maximum intensity at post-peak initial stage. Then the acoustic emission intensity decreases sharply. Acoustic emission maximum intensity lags behind the peak stress. The lag effect of acoustic emission maximum intensity relatively weakens along with the increasing of intermediate principal stress. Acoustic emission maximum intensity duration becomes longer with the increase of intermediate principal stress.
This paper investigates coal strength and damage charateristics under bidirectional loading, obtains the mechanical parameters by testing the coal under uniaxial compression, then gets coal mesomechanical parameters through particle flow code(PFC) and fish program combined with the uniaxial experimental results. It conducts the research on coal strength, deformation and acoustic emission under biaxial loading. The main research results are reached as follows. In coal deformation and failure process under bidirectional loading, intermediate principal stress has the most significant effect on the yield stage, but no effects on the post-peak softening stage, which is different from the effects confining compression on the post-peak softening stage under triaxial loading. This result shows that coal under biaxial loading basically does not have the features of brittle converting ductile in post-peak stage. Coal volumetric strain under biaxial loading shows the three stages of linear volumetric strain decrease, nonlinear expansion and linear expansion. Intermediate principal stress has the most significant effects on nonlinear expansion stage, but no effects on other two stages. In coal damage and failure process, acoustic emission linearly increases at elastic stage, but the growth rate is smaller, nonlinearly rapidly increases at yield stage. It has the fastest growing near peak, reaches the maximum intensity at post-peak initial stage. Then the acoustic emission intensity decreases sharply. Acoustic emission maximum intensity lags behind the peak stress. The lag effect of acoustic emission maximum intensity relatively weakens along with the increasing of intermediate principal stress. Acoustic emission maximum intensity duration becomes longer with the increase of intermediate principal stress.
2015, 23(6): 1066-1071.
The remolded loess with same dry density and different moisture contents are tested with confined compression test. Based on research methods of undisturbed loess collapsibility, effect of moisture content on deformation characteristics of the remolded loess is analyzed. The test results show that under low moisture content, the relationship between void ratio and stress is approximately linear. The relationship between secant modulus and stress is significant nonlinear. The strain velocity decays very rapid. Under high moisture content, the relationship between void ratio and stress is significantly nonlinear. The relationship between secant modulus and stress is approximately linear and the strain velocity decays slowly.
The remolded loess with same dry density and different moisture contents are tested with confined compression test. Based on research methods of undisturbed loess collapsibility, effect of moisture content on deformation characteristics of the remolded loess is analyzed. The test results show that under low moisture content, the relationship between void ratio and stress is approximately linear. The relationship between secant modulus and stress is significant nonlinear. The strain velocity decays very rapid. Under high moisture content, the relationship between void ratio and stress is significantly nonlinear. The relationship between secant modulus and stress is approximately linear and the strain velocity decays slowly.
2015, 23(6): 1072-1078.
This paper aims to understand the deformation characteristics of shield tunnel wall rock in soft soil. It builds a three-dimensional numerical model of every step of analyzing tunneling shield dynamic. The model is combined with the engineering example of one city subway shield tunnel under the existing bridge structure. The model is based on the consolidation finite element equation, Coulomb yield criterion and Darcy's law of pore water. It considers many factors that affect the quality of shield construction. The factors include cutter torque, propulsion, soil pressure, bridge foundation load, pore water pressure. The model is combined with triaxial experiments and field data. Issues in dynamic process of shield tunneling including the principle of modeling, the model rationality, the deformation characteristics of wall rock, and the safety of bridge structure, are studied in the model. The results show the follows. The process that shield tunneling affects the deformation of wall rock should be divided into three stages, approaching, passing through and leaving. When the shield tunneling approaches the section, the front surface appears arched under the influence of the cutter torque, propulsion and soil pressure when the shield tunneling approaches the section. When the shield passes through or leaves the section, the wall rock trends to settle, compress into the tunnel and compress forward, and the deformation is mainly at the top of the entrance to the hole, appearing agroove type. The calculated settlement of surface and abutment tallies with test results. The deformation of wall rock can meet the safety requirement of shield tunneling.
This paper aims to understand the deformation characteristics of shield tunnel wall rock in soft soil. It builds a three-dimensional numerical model of every step of analyzing tunneling shield dynamic. The model is combined with the engineering example of one city subway shield tunnel under the existing bridge structure. The model is based on the consolidation finite element equation, Coulomb yield criterion and Darcy's law of pore water. It considers many factors that affect the quality of shield construction. The factors include cutter torque, propulsion, soil pressure, bridge foundation load, pore water pressure. The model is combined with triaxial experiments and field data. Issues in dynamic process of shield tunneling including the principle of modeling, the model rationality, the deformation characteristics of wall rock, and the safety of bridge structure, are studied in the model. The results show the follows. The process that shield tunneling affects the deformation of wall rock should be divided into three stages, approaching, passing through and leaving. When the shield tunneling approaches the section, the front surface appears arched under the influence of the cutter torque, propulsion and soil pressure when the shield tunneling approaches the section. When the shield passes through or leaves the section, the wall rock trends to settle, compress into the tunnel and compress forward, and the deformation is mainly at the top of the entrance to the hole, appearing agroove type. The calculated settlement of surface and abutment tallies with test results. The deformation of wall rock can meet the safety requirement of shield tunneling.
2015, 23(6): 1079-1084.
Driving PHC pile through deep dense sand conditions often causes damage to the pile. The pile can't be drived into the design depth. Driving PHC pile through deep dense sand layer is analyzed using GRLWEAP for comprehensive analysis of these conditions of PHC pile to drive. The high strain monitoring test is also carried out. The research finds that it is feasible to drive the PHC pile through deep dense sand layer with reasonable selection of pile driving system and driving technology. Besides, it is necessary to take guide-hole measures and strengthen the pile body and pile shoe of PHC pile. The findings can provide a scientific basis for the design and construction of PHC pile in deep dense sand conditions.
Driving PHC pile through deep dense sand conditions often causes damage to the pile. The pile can't be drived into the design depth. Driving PHC pile through deep dense sand layer is analyzed using GRLWEAP for comprehensive analysis of these conditions of PHC pile to drive. The high strain monitoring test is also carried out. The research finds that it is feasible to drive the PHC pile through deep dense sand layer with reasonable selection of pile driving system and driving technology. Besides, it is necessary to take guide-hole measures and strengthen the pile body and pile shoe of PHC pile. The findings can provide a scientific basis for the design and construction of PHC pile in deep dense sand conditions.
2015, 23(6): 1085-1092.
Soil pressure is an important parameter in geological engineering and related model test applications. Although many currently soil pressure sensors can meet most of the requirements for soil pressure monitoring of practical engineering, limitations still exist in measuring soil pressure for geological model test, especially for those model test containing underground water. Fiber Bragg Grating(FBG) is small in size, easy to encapsulate into sensor, waterproof, non-corrosive, and resistive to Electric-Magnetic Interference(EMI).It is a promising sensing element for monitoring key parameters of geological model tests. In this paper, a miniature FBG soil pressure sensor is customized for geological model test to counter the issues mentioned above.It is developed utilizing short-gauge FBG.Finite Element Simulation is adopted for the optimization of sensor's performance. Some specifications including size of diagram and the thickness-diameter ratio of the sensor are designed based on the simulation result so as to get better sensitivity and reliability. The simulating results indicate that a cylinder flat diagram with the diameter of 20mm and the thickness of 0.2mm can provide higher sensitivity for the sensor and minimize the FBG spectrum chirp induced by non-uniform of strain distribution. Moreover, the sensor with the thickness-diameter ratio of 0.16(H/D(4mm/25mm)) can contribute to less interfere to the medium to be measured. It will provide more reliable soil pressure measurement results. To verify the performance of designed sensor, both pressure calibration experiments and temperature experiments are conducted. Air pressure calibration system consisting high accuracy digital pressure gauge and air pressure pump is used to calibrate the sensor in the pressure range of 0~1MPa and to verify the repeatability and consistency. The results demonstrate that the designed sensor exhibits desirable repeatability and consistency. The temperature experiments show that although temperature sensitivity of the designed soil pressure sensor is slightly higher than the bared FBG,the sensor's linearity is good and the temperature induced wavelength variation can be compensated with extra strain-independent FBG sensor. Finally, the designed soil pressure sensors are utilized in a subsea tunnel model test to monitor the stress of surrounding rock during the tunnel excavation. Stress measured by the sensors fluctuates slightly at the beginning of excavation, and then decreases rapidly when the tunnel face is passing the stress monitoring section. After the tunnel face passes the monitoring section, the stress stabilizes gradually. The tendency indicates that the tunnel becomes instable rapidly due to the excavation and then gradually stabilizes. The variation of stress during the whole process is traced by miniature FBG soil pressure sensor, which verifies its feasibility for model test.
Soil pressure is an important parameter in geological engineering and related model test applications. Although many currently soil pressure sensors can meet most of the requirements for soil pressure monitoring of practical engineering, limitations still exist in measuring soil pressure for geological model test, especially for those model test containing underground water. Fiber Bragg Grating(FBG) is small in size, easy to encapsulate into sensor, waterproof, non-corrosive, and resistive to Electric-Magnetic Interference(EMI).It is a promising sensing element for monitoring key parameters of geological model tests. In this paper, a miniature FBG soil pressure sensor is customized for geological model test to counter the issues mentioned above.It is developed utilizing short-gauge FBG.Finite Element Simulation is adopted for the optimization of sensor's performance. Some specifications including size of diagram and the thickness-diameter ratio of the sensor are designed based on the simulation result so as to get better sensitivity and reliability. The simulating results indicate that a cylinder flat diagram with the diameter of 20mm and the thickness of 0.2mm can provide higher sensitivity for the sensor and minimize the FBG spectrum chirp induced by non-uniform of strain distribution. Moreover, the sensor with the thickness-diameter ratio of 0.16(H/D(4mm/25mm)) can contribute to less interfere to the medium to be measured. It will provide more reliable soil pressure measurement results. To verify the performance of designed sensor, both pressure calibration experiments and temperature experiments are conducted. Air pressure calibration system consisting high accuracy digital pressure gauge and air pressure pump is used to calibrate the sensor in the pressure range of 0~1MPa and to verify the repeatability and consistency. The results demonstrate that the designed sensor exhibits desirable repeatability and consistency. The temperature experiments show that although temperature sensitivity of the designed soil pressure sensor is slightly higher than the bared FBG,the sensor's linearity is good and the temperature induced wavelength variation can be compensated with extra strain-independent FBG sensor. Finally, the designed soil pressure sensors are utilized in a subsea tunnel model test to monitor the stress of surrounding rock during the tunnel excavation. Stress measured by the sensors fluctuates slightly at the beginning of excavation, and then decreases rapidly when the tunnel face is passing the stress monitoring section. After the tunnel face passes the monitoring section, the stress stabilizes gradually. The tendency indicates that the tunnel becomes instable rapidly due to the excavation and then gradually stabilizes. The variation of stress during the whole process is traced by miniature FBG soil pressure sensor, which verifies its feasibility for model test.
2015, 23(6): 1093-1099.
The pore pressure behavior of soils nearby the tunnel of Shanghai Metro Line 9 was investigated chronically. The results show that excess pore pressure generates rapidly when the train vibration loading is applied. The excess pore pressure is about 1.2kPa at arch waist depth. After the last train passes through, the pore pressure starts dissipating. By the time that the last train passes 5minutes, excess pore pressure dissipates 80 percent. The excess pore pressure generated by shield construction is much higher than that of metro vibration. Site testing mainly shows the excess pore pressure dissipation. The distributions of excess pore pressure are as follows:above tunnel vault pore pressure increases with depth; below the tunnel vault, pore pressure reduces as the depth increase; surround the tunnel vault, pore pressure is larger and pore pressure contours are denser.
The pore pressure behavior of soils nearby the tunnel of Shanghai Metro Line 9 was investigated chronically. The results show that excess pore pressure generates rapidly when the train vibration loading is applied. The excess pore pressure is about 1.2kPa at arch waist depth. After the last train passes through, the pore pressure starts dissipating. By the time that the last train passes 5minutes, excess pore pressure dissipates 80 percent. The excess pore pressure generated by shield construction is much higher than that of metro vibration. Site testing mainly shows the excess pore pressure dissipation. The distributions of excess pore pressure are as follows:above tunnel vault pore pressure increases with depth; below the tunnel vault, pore pressure reduces as the depth increase; surround the tunnel vault, pore pressure is larger and pore pressure contours are denser.
2015, 23(6): 1100-1108.
Physical model test is one of the most important means for scientific researching of rock and soil mechanics and engineering geology. Optical fiber sensing(OFS) is a testing technology which possesses the specialty of high accuracy, real-time, distributed and parallel. The establishment of physical model test with OFS method promotes the progress of experimental modelling technique, and provides a more precisely reliable and entirely meticulous scientific instruction for field practicing and construction. This paper lists the most commonly used techniques of physical model test with OFS.Its progress in five main engineering areas of rock mechanics and engineering is reviewed. The key application issues that structural forms and technologies of temperature compensation, optical fiber sensors calibration and layout are analyzed. The correlations among optical fiber, physical model, and different layouts techniques are discussed. The research of multiple sizes and multi-source information model test with OFS will be a hotspot of indoor experimental modelling in rock and soild mechanics and engineering geology.
Physical model test is one of the most important means for scientific researching of rock and soil mechanics and engineering geology. Optical fiber sensing(OFS) is a testing technology which possesses the specialty of high accuracy, real-time, distributed and parallel. The establishment of physical model test with OFS method promotes the progress of experimental modelling technique, and provides a more precisely reliable and entirely meticulous scientific instruction for field practicing and construction. This paper lists the most commonly used techniques of physical model test with OFS.Its progress in five main engineering areas of rock mechanics and engineering is reviewed. The key application issues that structural forms and technologies of temperature compensation, optical fiber sensors calibration and layout are analyzed. The correlations among optical fiber, physical model, and different layouts techniques are discussed. The research of multiple sizes and multi-source information model test with OFS will be a hotspot of indoor experimental modelling in rock and soild mechanics and engineering geology.
2015, 23(6): 1109-1116.
According to the deformation properties and geological conditions at field, the factors affect the toppling deformation of rock mass are analyzed. Contrasted to the real deformation strength, which exposed by excavated slope, the numerical simulation method called UDEC is used to simulate the toppling strength along the limit depth. The factors, time-dependent process and distribution are researched. The research result is that the external factors are gravity force, earth stress, unloading direction and magnitude. A calculating model of limited toppling depth according to the shallow deformation strength is put forward based on geological mechanism analysis, numerical method and formula reduction.
According to the deformation properties and geological conditions at field, the factors affect the toppling deformation of rock mass are analyzed. Contrasted to the real deformation strength, which exposed by excavated slope, the numerical simulation method called UDEC is used to simulate the toppling strength along the limit depth. The factors, time-dependent process and distribution are researched. The research result is that the external factors are gravity force, earth stress, unloading direction and magnitude. A calculating model of limited toppling depth according to the shallow deformation strength is put forward based on geological mechanism analysis, numerical method and formula reduction.
2015, 23(6): 1117-1126.
Rock-ice avalanches in high-mountain regions can have an extremely high mobility and an enormous destructive potential. The influence of ice is of critical importance to enhance the mobility of rock-ice avalanches. However, the role of ice during the mass movement processes has not been systematically investigated and the mechanisms leading to the typically long run-out distances of such events are not well understood. Based on field investigation and historical data analysis of Yigong landslide occurred in April 2000,a conclusion is drawn that Yigong landslide is a typical rock-ice avalanche with a huge volume and an extremely long run-out, which involved ice or snow from the beginning of the movement or due to entrainment. A series of flume tests are conducted to reproduce the propagation of roc-ice avalanches and to explain a group of holes located on the front of deposit which are observed in the field. Furthermore, the run-outs of granular avalanches with different ice contents and size ratios of rock and ice particles are measured. The results show that ice particles are possibly involved in the front mass of granular avalanches on their whole movement. Then they melt when the avalanches deposit. It is the possible cause of the formation of the holes in the deposit. The involved ice particles can enhance the mobility of rock-ice avalanches. However, the length of run-out would not increase but decrease in the condition of large ice contents due to the ice cohesive action which makes the ice particles become large ones and difficult to enter into granular avalanches. It is concluded that the entrainment of ice particles into the mass of granular avalanches plays an important role in enhancing the mobility. The smaller size ratio of ice and rock particles, the easier the ice particles entered into granular avalanches. This work contributes to a better understanding of the role of ice in enhancing the mobility of rock-ice avalanches, and also to provide a scientific guidance in preventing the hazards.
Rock-ice avalanches in high-mountain regions can have an extremely high mobility and an enormous destructive potential. The influence of ice is of critical importance to enhance the mobility of rock-ice avalanches. However, the role of ice during the mass movement processes has not been systematically investigated and the mechanisms leading to the typically long run-out distances of such events are not well understood. Based on field investigation and historical data analysis of Yigong landslide occurred in April 2000,a conclusion is drawn that Yigong landslide is a typical rock-ice avalanche with a huge volume and an extremely long run-out, which involved ice or snow from the beginning of the movement or due to entrainment. A series of flume tests are conducted to reproduce the propagation of roc-ice avalanches and to explain a group of holes located on the front of deposit which are observed in the field. Furthermore, the run-outs of granular avalanches with different ice contents and size ratios of rock and ice particles are measured. The results show that ice particles are possibly involved in the front mass of granular avalanches on their whole movement. Then they melt when the avalanches deposit. It is the possible cause of the formation of the holes in the deposit. The involved ice particles can enhance the mobility of rock-ice avalanches. However, the length of run-out would not increase but decrease in the condition of large ice contents due to the ice cohesive action which makes the ice particles become large ones and difficult to enter into granular avalanches. It is concluded that the entrainment of ice particles into the mass of granular avalanches plays an important role in enhancing the mobility. The smaller size ratio of ice and rock particles, the easier the ice particles entered into granular avalanches. This work contributes to a better understanding of the role of ice in enhancing the mobility of rock-ice avalanches, and also to provide a scientific guidance in preventing the hazards.
2015, 23(6): 1127-1137.
The Liujiapo landslide is controlled by Hongchunba-Zengjiaba fault. In order to study the formation mechanism of the landslide, based on the field investigation, a three-dimensional finite element numerical simulation model is established. The simulation results with Midas/GTS software show that the fault plays a controlling role of the landslide and the water triggers the occurrence of the landslide. The deformation mode of Liujiapo landslide is summarized as follows. The slope occurs shear failure on the west side where the fault crosses and the frontal zone moves forward to drive the deformation of the east side. As the free face lies in front of the slope, the landslide occurs when a through plane is formed. The results have certain reference function to prevent landslides under similar conditions in the future.
The Liujiapo landslide is controlled by Hongchunba-Zengjiaba fault. In order to study the formation mechanism of the landslide, based on the field investigation, a three-dimensional finite element numerical simulation model is established. The simulation results with Midas/GTS software show that the fault plays a controlling role of the landslide and the water triggers the occurrence of the landslide. The deformation mode of Liujiapo landslide is summarized as follows. The slope occurs shear failure on the west side where the fault crosses and the frontal zone moves forward to drive the deformation of the east side. As the free face lies in front of the slope, the landslide occurs when a through plane is formed. The results have certain reference function to prevent landslides under similar conditions in the future.
2015, 23(6): 1138-1145.
Regional geo-hazard susceptibility assessment is the basis for early warning of geo-hazards. Huairou district is located in the north of Beijing and has favorable geological conditions to rockfall. The widely developed rockfalls threat to the lives and property of local people. Therefore, the region rockfall susceptibility assessment is significantly meaningful. According to investigation, two forms of rockfall inventory maps including point distribution and area distribution for the same 688 rockfalls in Huairou district of Beijing are obtained on site. The rockfall inventory maps provide the necessary background information for building the susceptibility model, which affects the reliability of evaluation. In order to quantitatively assess rockfall susceptibility, frequency ratio(FR)model is applied using GIS.In general, to predict landslides, it is normally assumed that rockfall occurrence is determined by rockfall-related factors, and that future rockfalls will occur under the same conditions as past rockfalls. For the modeling, lithology, terrain, faults and roads construction are considered as significant rockfall-related factors in rockfall occurrences based on site investigation and statistical analysis. After assessing the susceptibility maps, validation is essential to determine the predictive value of susceptibility maps. It also helps to better select the most suitable function and significant variables, thus improving the efficiency of the mapping process. Validation can be performed using a rockfall population independent from the one used to construct the map. Therefore, FR model is run including only 415 rockfalls that randomly selected from the total rockfalls and then validated with respect to the left 273 rockfalls. The prediction-rate curve based on rockfall area inventory shows a better performance in prediction than that based on rockfall point inventory, which reveals that the uncertainty exists in rockfall point inventory. Based on the FR model using rockfall area inventory map, Huairou district is classified into five classes of rockfall susceptibility:very low susceptibility zone(14% of the whole area),low susceptibility zone(20%),medium susceptibility zone(27%),high susceptibility zone(22%), and very high susceptibility zone(17%).This study can provide reference for inventory mapping in regional rockfall susceptibility assessment. The susceptibility map can be a helpful tool for regional land use planning and disaster prevention and mitigation in Huairou district.
Regional geo-hazard susceptibility assessment is the basis for early warning of geo-hazards. Huairou district is located in the north of Beijing and has favorable geological conditions to rockfall. The widely developed rockfalls threat to the lives and property of local people. Therefore, the region rockfall susceptibility assessment is significantly meaningful. According to investigation, two forms of rockfall inventory maps including point distribution and area distribution for the same 688 rockfalls in Huairou district of Beijing are obtained on site. The rockfall inventory maps provide the necessary background information for building the susceptibility model, which affects the reliability of evaluation. In order to quantitatively assess rockfall susceptibility, frequency ratio(FR)model is applied using GIS.In general, to predict landslides, it is normally assumed that rockfall occurrence is determined by rockfall-related factors, and that future rockfalls will occur under the same conditions as past rockfalls. For the modeling, lithology, terrain, faults and roads construction are considered as significant rockfall-related factors in rockfall occurrences based on site investigation and statistical analysis. After assessing the susceptibility maps, validation is essential to determine the predictive value of susceptibility maps. It also helps to better select the most suitable function and significant variables, thus improving the efficiency of the mapping process. Validation can be performed using a rockfall population independent from the one used to construct the map. Therefore, FR model is run including only 415 rockfalls that randomly selected from the total rockfalls and then validated with respect to the left 273 rockfalls. The prediction-rate curve based on rockfall area inventory shows a better performance in prediction than that based on rockfall point inventory, which reveals that the uncertainty exists in rockfall point inventory. Based on the FR model using rockfall area inventory map, Huairou district is classified into five classes of rockfall susceptibility:very low susceptibility zone(14% of the whole area),low susceptibility zone(20%),medium susceptibility zone(27%),high susceptibility zone(22%), and very high susceptibility zone(17%).This study can provide reference for inventory mapping in regional rockfall susceptibility assessment. The susceptibility map can be a helpful tool for regional land use planning and disaster prevention and mitigation in Huairou district.
2015, 23(6): 1146-1152.
The distribution information of multi-fields in slope can be obtained using distributed optical fiber sensing(DFOS)technology. Nevertheless, it is still a quite complicated work to analyze massive amounts of information about multiple fields relatively, and to evaluate the slope stability under multi-fields coupling effect. This paper introduces the basic principle of analysis method of association rules in data mining. It designs distributed optical fiber monitoring projects on strain field, deformation field, seepage field, temperature field, environmental parameter of slope respectively. Taking Majiagou slope of Three Gorges as an example, this paper analyzes monitoring data of different fields with the method of data mining association rules, and it finds rules on matching attribute between monitoring time and fluctuation of reservoir water level, coordination between fluctuation of reservoir water level and groundwater level of slope's leading edge. Comparing with practical monitoring data, it proves that it is effective to analyze multiple fields of slope by adopting association rules, thereby providing scientific basis for slope stability evaluation and landslide forecast warning.
The distribution information of multi-fields in slope can be obtained using distributed optical fiber sensing(DFOS)technology. Nevertheless, it is still a quite complicated work to analyze massive amounts of information about multiple fields relatively, and to evaluate the slope stability under multi-fields coupling effect. This paper introduces the basic principle of analysis method of association rules in data mining. It designs distributed optical fiber monitoring projects on strain field, deformation field, seepage field, temperature field, environmental parameter of slope respectively. Taking Majiagou slope of Three Gorges as an example, this paper analyzes monitoring data of different fields with the method of data mining association rules, and it finds rules on matching attribute between monitoring time and fluctuation of reservoir water level, coordination between fluctuation of reservoir water level and groundwater level of slope's leading edge. Comparing with practical monitoring data, it proves that it is effective to analyze multiple fields of slope by adopting association rules, thereby providing scientific basis for slope stability evaluation and landslide forecast warning.
2015, 23(6): 1153-1159.
Sensitivity analysis of landslide parameters is the foundation of the landslide mechanism analysis and quantitative evaluation. The sensitivity coefficient method, the sensitivity function method and the orthogonal test method are the three most common methods in sensitivity analysis of landslide parameters. However, it is not clear whether the three methods would have the same results with the same input data. This paper takes the mechanical parameters of the slipzone of Xieliupo landslide as an example. Sensitivity analysis is made using the three different methods. Although the results are not the same, the Maxwell viscosity is identified as the most sensitive parameter by all the methods. The sensitivity coefficient method and the sensitivity function method are often limited to the cases with fewer parameters. The result by the orthogonal method is considered more reasonable for the slow moving landslide with multiple mechanical parameters.
Sensitivity analysis of landslide parameters is the foundation of the landslide mechanism analysis and quantitative evaluation. The sensitivity coefficient method, the sensitivity function method and the orthogonal test method are the three most common methods in sensitivity analysis of landslide parameters. However, it is not clear whether the three methods would have the same results with the same input data. This paper takes the mechanical parameters of the slipzone of Xieliupo landslide as an example. Sensitivity analysis is made using the three different methods. Although the results are not the same, the Maxwell viscosity is identified as the most sensitive parameter by all the methods. The sensitivity coefficient method and the sensitivity function method are often limited to the cases with fewer parameters. The result by the orthogonal method is considered more reasonable for the slow moving landslide with multiple mechanical parameters.
2015, 23(6): 1160-1167.
Karst cave disposing is crucial for pile foundation construction in karst area. This paper systematically summarizes the influence of Karst cave to pile foundation, the principle of Karst cave disposing and the basis on selection of disposal methods. As an example, the pile foundation construction of the Yonghe Bridge in Ji'an City, is taken to show how to choose the optimal strategy in practical projects. The geologic conditions, surrounding environments, and project issues(safety, quality, construction schedule and costs) are taken into account. The scheme in practice shows good results in preventing large ground subsidence, ensuring the stability of hole wall, and improving the quality of the piles. The study provides a reference for the similar projects of Karst cave treatment in the future.
Karst cave disposing is crucial for pile foundation construction in karst area. This paper systematically summarizes the influence of Karst cave to pile foundation, the principle of Karst cave disposing and the basis on selection of disposal methods. As an example, the pile foundation construction of the Yonghe Bridge in Ji'an City, is taken to show how to choose the optimal strategy in practical projects. The geologic conditions, surrounding environments, and project issues(safety, quality, construction schedule and costs) are taken into account. The scheme in practice shows good results in preventing large ground subsidence, ensuring the stability of hole wall, and improving the quality of the piles. The study provides a reference for the similar projects of Karst cave treatment in the future.
2015, 23(6): 1168-1174.
Based on the experiment data of the in-situ test of FEBEX,the CODE-BRIGHT is used to simulate the near field of nuclear waste repository and to investigates the change rule of suction and displacement in different coupling forms of Thermo-hydro-mechanical. After comparing the suction and displacement in these coupling forms, we can analyze the main factors that are to influence them. The results can show the character of buffer layer of nuclear waste disposal repository and provides a suitable and simple coupling form for the calculation of project.
Based on the experiment data of the in-situ test of FEBEX,the CODE-BRIGHT is used to simulate the near field of nuclear waste repository and to investigates the change rule of suction and displacement in different coupling forms of Thermo-hydro-mechanical. After comparing the suction and displacement in these coupling forms, we can analyze the main factors that are to influence them. The results can show the character of buffer layer of nuclear waste disposal repository and provides a suitable and simple coupling form for the calculation of project.
2015, 23(6): 1175-1181.
This paper aims to comprehend the dynamic mechanics performance of argillaceous siltstone in the moisture conditions. It carries out the split Hopkinson pressure bar test on argillaceous siltstone under different impact speeds. The energy dissipation characteristics of the samples are carefully analyzed. The results show that the loading rate and moisture condition play a great role on the failure of rock samples. The change of moisture content has a great influence on energy dissipation characteristics of the rock sample under the same impact load. The higher the impact rate, the higher the strain rate of the specimens. The greater moisture content, the specific energy absorption and the degree of fragmentation also become higher, the average lumpiness of fragmentation becomes smaller. Change of water content is the main factor that leads to the change of fracture toughness. Increase of moisture content leads to the reduction of the fracture toughness of the specimen, which will result in breaking into smaller pieces more easily.
This paper aims to comprehend the dynamic mechanics performance of argillaceous siltstone in the moisture conditions. It carries out the split Hopkinson pressure bar test on argillaceous siltstone under different impact speeds. The energy dissipation characteristics of the samples are carefully analyzed. The results show that the loading rate and moisture condition play a great role on the failure of rock samples. The change of moisture content has a great influence on energy dissipation characteristics of the rock sample under the same impact load. The higher the impact rate, the higher the strain rate of the specimens. The greater moisture content, the specific energy absorption and the degree of fragmentation also become higher, the average lumpiness of fragmentation becomes smaller. Change of water content is the main factor that leads to the change of fracture toughness. Increase of moisture content leads to the reduction of the fracture toughness of the specimen, which will result in breaking into smaller pieces more easily.
2015, 23(6): 1182-1188.
The Balangkou hydropower station locates on the tributary of the Dadu River and is a diversion station. The content of the sand and gravel filling materials with P5(particle size less than 5mm) is relatively high, which may influence the stability of dam. The rolling test is carried out in the construction site. This test determines the suitable filling thickness as 97cm. And the density, moisture content and settlement are measured as well during the rolling test. In addition, the grain content test, compaction test, penetration test and large triaxial test are carried out in laboratory. The grain content test shows that the sand and gravel are well graded and can meet the embankment dam design requirements. The optimum water content and maximum dry density are 5.32% and 2.42gcm-3 respectively. They are determined with compaction test. The average permeability coefficient is 2. 42210-2cms-1, which is obtained with penetration test. The strength parameters of the filling materials are =37. 711 and c=0,which is got with triaxial test. According to the test results, this study also checks the dam settlement, stress, seepage and stability comprehensively. The test results provide some guides for the long-term operation of the Balangkou Hydropower Station.
The Balangkou hydropower station locates on the tributary of the Dadu River and is a diversion station. The content of the sand and gravel filling materials with P5(particle size less than 5mm) is relatively high, which may influence the stability of dam. The rolling test is carried out in the construction site. This test determines the suitable filling thickness as 97cm. And the density, moisture content and settlement are measured as well during the rolling test. In addition, the grain content test, compaction test, penetration test and large triaxial test are carried out in laboratory. The grain content test shows that the sand and gravel are well graded and can meet the embankment dam design requirements. The optimum water content and maximum dry density are 5.32% and 2.42gcm-3 respectively. They are determined with compaction test. The average permeability coefficient is 2. 42210-2cms-1, which is obtained with penetration test. The strength parameters of the filling materials are =37. 711 and c=0,which is got with triaxial test. According to the test results, this study also checks the dam settlement, stress, seepage and stability comprehensively. The test results provide some guides for the long-term operation of the Balangkou Hydropower Station.
2015, 23(6): 1189-1195.
Stability evaluation of tailing dam is the key procedure for tailing pond construction. The mineral types of tailings are quite complex, and are regional dependent. The characteristics of tailings are largely affected by mineral types, producing processes and deposited environments. This paper examines an ongoing designed iron mine tailings pond. It locates at Southwestern China. Specifically, this paper conducts a large number of physical and mechanical experiments for coarse and fine tailing materials, and obtained physical and mechanical parameters and applies them into tailing dam numerical simulation. It analyzes the stress and deformation properties of this tailing dam, and stability at different deposit elevations and different operation conditions. Furthermore, the quasi-static method is adopted to analyze the dynamic response of tailing dam under earthquake condition. Results show that coarse tailings present dilatancy and softening properties. In contrast, the dilatancy of fine tailings is not apparent. Compressive stress is commonly present inside tailing dam. There is a small part tensile stress area that appears on the surface of tailing dam. Tailing dam tends to happen deep slide at higher deposit elevation conditions. Additionally, the length of dry-beach has significant effects on dam stability. The ratio of dam stability increases with the increase of the length of dry-beach. In the end, some specific measures and suggestions are proposed for the tailing dam's safely operation. The results of this paper can provide a scientific basis for tailing dam design, construction and safely operation.
Stability evaluation of tailing dam is the key procedure for tailing pond construction. The mineral types of tailings are quite complex, and are regional dependent. The characteristics of tailings are largely affected by mineral types, producing processes and deposited environments. This paper examines an ongoing designed iron mine tailings pond. It locates at Southwestern China. Specifically, this paper conducts a large number of physical and mechanical experiments for coarse and fine tailing materials, and obtained physical and mechanical parameters and applies them into tailing dam numerical simulation. It analyzes the stress and deformation properties of this tailing dam, and stability at different deposit elevations and different operation conditions. Furthermore, the quasi-static method is adopted to analyze the dynamic response of tailing dam under earthquake condition. Results show that coarse tailings present dilatancy and softening properties. In contrast, the dilatancy of fine tailings is not apparent. Compressive stress is commonly present inside tailing dam. There is a small part tensile stress area that appears on the surface of tailing dam. Tailing dam tends to happen deep slide at higher deposit elevation conditions. Additionally, the length of dry-beach has significant effects on dam stability. The ratio of dam stability increases with the increase of the length of dry-beach. In the end, some specific measures and suggestions are proposed for the tailing dam's safely operation. The results of this paper can provide a scientific basis for tailing dam design, construction and safely operation.
2015, 23(6): 1196-1201.
Geothermal resources is one kind of clean and renewable energy which has been used widely. But, designing and building of underground engineering become more difficulty in the area of geothermal resources, because geothermal resources can lead to high geo-temperature phenomenon of engineering geological problem. This problem has been encountered during construction of many underground engineering at home and abroad. Of these engineering, Bulunkou-Gonggeer hydroelectric power diversion tunnel and Qirehater hydroelectric power diversion tunnel located on Kala-Kunlun Mountain of Pamirs can be as typical engineering. During construction of Bulunkou-Gonggeer hydroelectric power diversion tunnel, the highest temperature of wall rock mass of tunnel is 97℃, and the highest temperature of steam water ejecting from joints and fissures is 140℃,the length of high geo-temperature tunnel is 4km. As for as Qirehater hydroelectric power diversion tunnel is concerned, the highest temperature of wall rock mass of tunnel is 119℃, and the highest temperature of steam water ejecting from joints and fissures is 174℃,the length of high geo-temperature tunnel is 3.5km. The length of tunnel whose temperature wall rock mass of tunnel exceeds 90℃is larger than 900m. High geo-temperature problem of the two tunnels is uncommon in the field of underground engineering. In this paper, cause of high geo-temperature of underground engineering in this area is talked about, authors consider that the main causes include activity regional structure, high regional heat flow background value, good rock conditions, poor underground water cyclic conditions, thermal conductivity rock mass or joint and small fault. Based on above discussion, authors consider that in the investigation stage of underground engineering, it is necessary to done that regional geothermal environment survey, thermal spring survey and geothermal parameters testing for those engineering which may encounter high geo-temperature during the period of designing and building. In this paper, author study high geo-temperature phenomenon which is one kind of uncommon and special geological problem during construction of underground engineering in home and abroad, activity regional structural environment and high regional heat flow background value are the essential reasons which lead to high geo-temperature phenomenon of underground engineering.
Geothermal resources is one kind of clean and renewable energy which has been used widely. But, designing and building of underground engineering become more difficulty in the area of geothermal resources, because geothermal resources can lead to high geo-temperature phenomenon of engineering geological problem. This problem has been encountered during construction of many underground engineering at home and abroad. Of these engineering, Bulunkou-Gonggeer hydroelectric power diversion tunnel and Qirehater hydroelectric power diversion tunnel located on Kala-Kunlun Mountain of Pamirs can be as typical engineering. During construction of Bulunkou-Gonggeer hydroelectric power diversion tunnel, the highest temperature of wall rock mass of tunnel is 97℃, and the highest temperature of steam water ejecting from joints and fissures is 140℃,the length of high geo-temperature tunnel is 4km. As for as Qirehater hydroelectric power diversion tunnel is concerned, the highest temperature of wall rock mass of tunnel is 119℃, and the highest temperature of steam water ejecting from joints and fissures is 174℃,the length of high geo-temperature tunnel is 3.5km. The length of tunnel whose temperature wall rock mass of tunnel exceeds 90℃is larger than 900m. High geo-temperature problem of the two tunnels is uncommon in the field of underground engineering. In this paper, cause of high geo-temperature of underground engineering in this area is talked about, authors consider that the main causes include activity regional structure, high regional heat flow background value, good rock conditions, poor underground water cyclic conditions, thermal conductivity rock mass or joint and small fault. Based on above discussion, authors consider that in the investigation stage of underground engineering, it is necessary to done that regional geothermal environment survey, thermal spring survey and geothermal parameters testing for those engineering which may encounter high geo-temperature during the period of designing and building. In this paper, author study high geo-temperature phenomenon which is one kind of uncommon and special geological problem during construction of underground engineering in home and abroad, activity regional structural environment and high regional heat flow background value are the essential reasons which lead to high geo-temperature phenomenon of underground engineering.
2015, 23(6): 1202-1210.
The Southern Yellow Sea is identified as advantaged sea area for evaluation of nonprofit and strategic offshore oil and gas resources in China. Currently, the study on the sedimentary characteristics and geotechnical properties in the depth direction of seafloor sediment in the sea area is sparse. By measuring and analyzing the particle size and physical-mechanical properties of the sediment cores collected from 287 stations in June 2009 and June 2010,we obtain the spatial characteristics and geotechnical properties of seafloor sediment in the west-central area of southern Yellow Sea. Investigation indicates that the types of surficial seafloor sediment in the study area are very diverse. The surficial seafloor sediments in the southwest study area, where the sediments are easily scoured and become coarser due to strong hydrodynamic conditions, are mainly composed of silty sand and sandy silt with high mechanical strength and low compressibility. The surficial seafloor sediments in the northeast study area consist mostly of silty clay and clayey silt with low mechanical strength and high compressibility. Sediments are not uniform in the seafloor, and often composed of a few types of sediments interbedded. The variation of fundamental physical properties and mechanical properties of the sediment with depth is mainly related to sediment types, and secondly compaction. To a certain extent, the fitting function proposed in this study can be used to estimate the porosity of seafloor sediment in the study area if the compressional wave velocity is known.
The Southern Yellow Sea is identified as advantaged sea area for evaluation of nonprofit and strategic offshore oil and gas resources in China. Currently, the study on the sedimentary characteristics and geotechnical properties in the depth direction of seafloor sediment in the sea area is sparse. By measuring and analyzing the particle size and physical-mechanical properties of the sediment cores collected from 287 stations in June 2009 and June 2010,we obtain the spatial characteristics and geotechnical properties of seafloor sediment in the west-central area of southern Yellow Sea. Investigation indicates that the types of surficial seafloor sediment in the study area are very diverse. The surficial seafloor sediments in the southwest study area, where the sediments are easily scoured and become coarser due to strong hydrodynamic conditions, are mainly composed of silty sand and sandy silt with high mechanical strength and low compressibility. The surficial seafloor sediments in the northeast study area consist mostly of silty clay and clayey silt with low mechanical strength and high compressibility. Sediments are not uniform in the seafloor, and often composed of a few types of sediments interbedded. The variation of fundamental physical properties and mechanical properties of the sediment with depth is mainly related to sediment types, and secondly compaction. To a certain extent, the fitting function proposed in this study can be used to estimate the porosity of seafloor sediment in the study area if the compressional wave velocity is known.
2015, 23(6): 1211-1219.
The NSFC proposals and grants of engineering geology in 2015 were analyzed. The number of proposals has been increasing. The number of General Program proposals increased significantly in this year. The peer-review referees well handled the scale of peer-review on the proposals, especially the NSFC Young Scientists Fund. The age distribution of the applicant tends to be reasonable. There are reasonable varieties of funded ratio among different age group. The young scientists have not actively participated in the grants of National Science Fund for Distinguished Young yet. The applicants of Key Program tended to be older in age than average, and the Pis of Key Program turned out to be older severely.
The NSFC proposals and grants of engineering geology in 2015 were analyzed. The number of proposals has been increasing. The number of General Program proposals increased significantly in this year. The peer-review referees well handled the scale of peer-review on the proposals, especially the NSFC Young Scientists Fund. The age distribution of the applicant tends to be reasonable. There are reasonable varieties of funded ratio among different age group. The young scientists have not actively participated in the grants of National Science Fund for Distinguished Young yet. The applicants of Key Program tended to be older in age than average, and the Pis of Key Program turned out to be older severely.
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