Landslides in Tianshui Basin, Gansu Province, Northwest China, severely affect the local population and the economy;therefore,understanding their evolution and kinematics is of great interest for landslide risk assess...Landslides in Tianshui Basin, Gansu Province, Northwest China, severely affect the local population and the economy;therefore,understanding their evolution and kinematics is of great interest for landslide risk assessment and prevention. However, there is no unified classification standard for the types of loess landslides in Tianshui.In this study, we explored the landslide distribution and failure characteristics by means of field investigation,remotesensinginterpretation,geological mapping, drilling exploration and shearwave velocity tests, and established a database of Tianshui landslides. Our analysis shows that shear zones in mudstone usually develop in weak intercalated layers. Landslides occur mainly along the West Qinling faults on slopes with gradients of 10° to 25° and on southeast-and southwest-facing slopes.These landslides were classified into five types: loess landslides, loess–mudstone interface landslides, loess flow-slides, loess–mudstone plane landslides and loess–mudstone cutting landslides. We discussed the evolution and failure process of each landslide type and analyzed the formation mechanism and motion characteristics of large-scale landslides. The analysis results show that the landslides in the study area are characterized by a gentle slope, long runout and high risk. The relationship between the runout L and the vertical drop H of the large-scale landslides in the study area is L > 4 H. There are good correlations between the equivalent friction coefficient of largescale landslides and their maximum height, runout,area and volume. The sliding zone of large-scale landslides often develops in the bedrock contact zone or in a weak interlayer within mudstone. From microstructure analysis, undisturbed mudstone consists mainly of small aggregates with dispersed inter-aggregate pores, whereas sheared clay has a more homogeneous structure. Linear striations are well developed on shear surfaces, and the clay pores in those surfaces have a more uniform distribution than those in undisturbed clay.展开更多
The mechanical behavior of the joints inside a loess layer is greatly important in weak intercalation studies owing to its involvement in a wide range of landslides in the loess region in China.The shear behavior of t...The mechanical behavior of the joints inside a loess layer is greatly important in weak intercalation studies owing to its involvement in a wide range of landslides in the loess region in China.The shear behavior of the joints in the loess stratum during direct shear and cyclic loadings was investigated using the PFC2D discrete element software.Loess mudstone and mudstone with weak intercalated layer materials were subjected to direct testing,and cyclic shear tests were conducted with consideration to the influence of normal stress and shear velocity.The macroscopic properties and damage patterns were obtained for six numerical configurations;namely,loess-weathered mudstone with 0°,10°,and-10°joints and weathered mudstone with 0°,10°,and-10°weak intercalated layers.The numerical test results revealed that,in the direct shear tests,the shear stress and shear displacement of the samples increased with the normal stress.In the cyclic shear tests with a total cycle number N=20,the shear stress-shear strain curve of the six different configurations exhibited a hysteresis loop.The numerical tests also revealed that,under cyclic shear,the normal stress and shear velocity affected the shear strength.The degree of damage increased as the shear velocity decreased from 0.1 mm/s to 0.005 mm/s for all six numerical configurations.Compared with the damage pattern of the direct shear tests,the damage of the cyclic shear tests mainly comprised shear cracks and fractures,some shaking consolidation settlement and fewer shear strain occurred around the joints.In the direct shear tests,more compression cracks and fractures occurred in the samples.The damage mainly developed along the joints,and shearing-off damage occurred.The results obtained by this study further elucidate the failure mechanism and microscopic damage response of the joints in the loess stratum in Northwest China.展开更多
Information about the long-term spatiotemporal evolution of landslides can improve our understanding of the landslide development process and can help prevent landslide disasters.This paper describes the Xiaozhuang la...Information about the long-term spatiotemporal evolution of landslides can improve our understanding of the landslide development process and can help prevent landslide disasters.This paper describes the Xiaozhuang landslide triggered by a historical earthquake and rainfall in Tianshui,Northwest China.The landslide is dominated by rotational-sliding movement.Several new failures and many fissures formed in the landslide area as a result of the 2013 Ms 6.6 Minxian earthquake and rainfall.Accordingly,field investigations,borehole drilling,geotechnical laboratory tests,and numerical calculations were conducted to study the mechanism of the landslide and to forecast its stability.A triaxial creep test of the slip soil indicates that the axial deformation of the mudstone increases with increasing water content.Numerical simulations suggest that failure is prone to occur within the deep part of the landslide under earthquake conditions.If the input seismic acceleration exceeds 0.2 g,the landslide will become unstable.Furthermore,the horizontal peak ground acceleration near the surface of the landslide is greater than that at depth.During a strong earthquake,the unstable regions are primarily located in the middle of the landslide and at its crest.When the rainfall intensity rate is 200 mm/d,the factor of safety is 1.319 and a dangerous zone appears in the lower and middle parts of the landslide.展开更多
基金This study was sponsored by National Natural Science Foundation of China(Grant No.41902269 and No.41702343)Project of China geological survey(Grant No.DD20190717)The authors express their sincere thanks to the reviewers and editor for their help.
文摘Landslides in Tianshui Basin, Gansu Province, Northwest China, severely affect the local population and the economy;therefore,understanding their evolution and kinematics is of great interest for landslide risk assessment and prevention. However, there is no unified classification standard for the types of loess landslides in Tianshui.In this study, we explored the landslide distribution and failure characteristics by means of field investigation,remotesensinginterpretation,geological mapping, drilling exploration and shearwave velocity tests, and established a database of Tianshui landslides. Our analysis shows that shear zones in mudstone usually develop in weak intercalated layers. Landslides occur mainly along the West Qinling faults on slopes with gradients of 10° to 25° and on southeast-and southwest-facing slopes.These landslides were classified into five types: loess landslides, loess–mudstone interface landslides, loess flow-slides, loess–mudstone plane landslides and loess–mudstone cutting landslides. We discussed the evolution and failure process of each landslide type and analyzed the formation mechanism and motion characteristics of large-scale landslides. The analysis results show that the landslides in the study area are characterized by a gentle slope, long runout and high risk. The relationship between the runout L and the vertical drop H of the large-scale landslides in the study area is L > 4 H. There are good correlations between the equivalent friction coefficient of largescale landslides and their maximum height, runout,area and volume. The sliding zone of large-scale landslides often develops in the bedrock contact zone or in a weak interlayer within mudstone. From microstructure analysis, undisturbed mudstone consists mainly of small aggregates with dispersed inter-aggregate pores, whereas sheared clay has a more homogeneous structure. Linear striations are well developed on shear surfaces, and the clay pores in those surfaces have a more uniform distribution than those in undisturbed clay.
基金sponsored by National Natural Science Foundation of China(No.41902269)Chinese Universities Scientific Fund(2020TC095)。
文摘The mechanical behavior of the joints inside a loess layer is greatly important in weak intercalation studies owing to its involvement in a wide range of landslides in the loess region in China.The shear behavior of the joints in the loess stratum during direct shear and cyclic loadings was investigated using the PFC2D discrete element software.Loess mudstone and mudstone with weak intercalated layer materials were subjected to direct testing,and cyclic shear tests were conducted with consideration to the influence of normal stress and shear velocity.The macroscopic properties and damage patterns were obtained for six numerical configurations;namely,loess-weathered mudstone with 0°,10°,and-10°joints and weathered mudstone with 0°,10°,and-10°weak intercalated layers.The numerical test results revealed that,in the direct shear tests,the shear stress and shear displacement of the samples increased with the normal stress.In the cyclic shear tests with a total cycle number N=20,the shear stress-shear strain curve of the six different configurations exhibited a hysteresis loop.The numerical tests also revealed that,under cyclic shear,the normal stress and shear velocity affected the shear strength.The degree of damage increased as the shear velocity decreased from 0.1 mm/s to 0.005 mm/s for all six numerical configurations.Compared with the damage pattern of the direct shear tests,the damage of the cyclic shear tests mainly comprised shear cracks and fractures,some shaking consolidation settlement and fewer shear strain occurred around the joints.In the direct shear tests,more compression cracks and fractures occurred in the samples.The damage mainly developed along the joints,and shearing-off damage occurred.The results obtained by this study further elucidate the failure mechanism and microscopic damage response of the joints in the loess stratum in Northwest China.
基金sponsored by National Natural Science Foundation of China(No.41902269)Chinese Universities Scientific Fund(2020TC095)。
文摘Information about the long-term spatiotemporal evolution of landslides can improve our understanding of the landslide development process and can help prevent landslide disasters.This paper describes the Xiaozhuang landslide triggered by a historical earthquake and rainfall in Tianshui,Northwest China.The landslide is dominated by rotational-sliding movement.Several new failures and many fissures formed in the landslide area as a result of the 2013 Ms 6.6 Minxian earthquake and rainfall.Accordingly,field investigations,borehole drilling,geotechnical laboratory tests,and numerical calculations were conducted to study the mechanism of the landslide and to forecast its stability.A triaxial creep test of the slip soil indicates that the axial deformation of the mudstone increases with increasing water content.Numerical simulations suggest that failure is prone to occur within the deep part of the landslide under earthquake conditions.If the input seismic acceleration exceeds 0.2 g,the landslide will become unstable.Furthermore,the horizontal peak ground acceleration near the surface of the landslide is greater than that at depth.During a strong earthquake,the unstable regions are primarily located in the middle of the landslide and at its crest.When the rainfall intensity rate is 200 mm/d,the factor of safety is 1.319 and a dangerous zone appears in the lower and middle parts of the landslide.
