2018 Vol. 26, No. 1

Others
It's well known that engineering geology has been playing an important role in the engineering construction of our country. Particularly, the authors have noticed that more and more importance has been attached to the three research areas of rock weathering, ancient geological engineering and geological disaster prevention and control. These three new research directions appear respectively, corresponding to the test and evaluation of rock weathering velocity, the research on engineering geology mechanics of large ancient underground caverns, and the mountain tourism planning served engineering geology method for prevention and control of the geological disasters of mountain tourism. It's well known that engineering geology has been playing an important role in the engineering construction of our country. Particularly, the authors have noticed that more and more importance has been attached to the three research areas of rock weathering, ancient geological engineering and geological disaster prevention and control. These three new research directions appear respectively, corresponding to the test and evaluation of rock weathering velocity, the research on engineering geology mechanics of large ancient underground caverns, and the mountain tourism planning served engineering geology method for prevention and control of the geological disasters of mountain tourism.
This paper is based on the observation and the analysis of the geological phenomena of the rock mass in engineering states. It has studied and summarized some results of physical and numerical models and developed the 12 kinds of qualitative effects of the discontinuities on the mechanical behavior and actions, and then explained and discussed them respectively. This paper is based on the observation and the analysis of the geological phenomena of the rock mass in engineering states. It has studied and summarized some results of physical and numerical models and developed the 12 kinds of qualitative effects of the discontinuities on the mechanical behavior and actions, and then explained and discussed them respectively.
The spatial characterization of micro-cracks and their relationship with the mineral composition in the gas shale can provide scientific guidance for the shale gas exploration. However, there has been little research on this problem because of the limitation of experiment instruments. In this study, two samples from Longmaxi Shale, which had been preserved in Sichuan Basin since Silurian, are imaged using the high performance field Scanning Electron Microscope(SEM) and energy dispersive X-ray spectrometer(EDS). Triaxial compression test is conducted on one of the two samples which called compressed sample, while the other sample remains undistrubed. The SEM and EDS are ZEISS MERLIN SEM equipped with secondary electron(SE)detectors for crack investigations at a pixel size of 10 nm and Bruker QUANTAX energy dispersive X-ray spectrometer(EDS)system for automatic identification of minerals at a pixel size of 1 μm. The scanning area is 1 mm. Based on this, the micro-and nanoscale micro-cracks before and after triaxial compression test are characterized by spatial analysis methods. The relationship between micro-fractures and mineral compositions is also investigated. Results show that the spatial distribution of all micro-cracks in both disturbed and undisturbed samples follows the power law indicating the nature of self-organization and structural hierarchy of spatial distrubiton of micro-cracks in shale. However, the parameters of the distribution(D and logC) vary distinctly with the mineral types(quartz, feldspar, carbonate and clay) implicating that different minerals have different mechanisms in response to mechanical loading and thus different contributions to the shale fracturing. Some brittle minerals such as feldspar and carbonate and their interaction with clay may play vital role in shale fracturing. The transition from tensile failure to shearing failure dominates the failure patterns for all minerals under mechanical loading. However, the cracking spatial characterization and fracturing mechanism vary among different minerals. The spatial distribution of micro-cracks concerning carbonate minerals and clay mineral changes dramatically before and after triaxial compression test and more complicated crack networks could form. Multiple failure mechanisms could co-exist within single mineral due to the complex stress condition under triaxial compression test. The high uncertainty of failure process should be taken into account due to the complicated mineral composition and structure. The spatial characterization of micro-cracks and their relationship with the mineral composition in the gas shale can provide scientific guidance for the shale gas exploration. However, there has been little research on this problem because of the limitation of experiment instruments. In this study, two samples from Longmaxi Shale, which had been preserved in Sichuan Basin since Silurian, are imaged using the high performance field Scanning Electron Microscope(SEM) and energy dispersive X-ray spectrometer(EDS). Triaxial compression test is conducted on one of the two samples which called compressed sample, while the other sample remains undistrubed. The SEM and EDS are ZEISS MERLIN SEM equipped with secondary electron(SE)detectors for crack investigations at a pixel size of 10 nm and Bruker QUANTAX energy dispersive X-ray spectrometer(EDS)system for automatic identification of minerals at a pixel size of 1 μm. The scanning area is 1 mm. Based on this, the micro-and nanoscale micro-cracks before and after triaxial compression test are characterized by spatial analysis methods. The relationship between micro-fractures and mineral compositions is also investigated. Results show that the spatial distribution of all micro-cracks in both disturbed and undisturbed samples follows the power law indicating the nature of self-organization and structural hierarchy of spatial distrubiton of micro-cracks in shale. However, the parameters of the distribution(D and logC) vary distinctly with the mineral types(quartz, feldspar, carbonate and clay) implicating that different minerals have different mechanisms in response to mechanical loading and thus different contributions to the shale fracturing. Some brittle minerals such as feldspar and carbonate and their interaction with clay may play vital role in shale fracturing. The transition from tensile failure to shearing failure dominates the failure patterns for all minerals under mechanical loading. However, the cracking spatial characterization and fracturing mechanism vary among different minerals. The spatial distribution of micro-cracks concerning carbonate minerals and clay mineral changes dramatically before and after triaxial compression test and more complicated crack networks could form. Multiple failure mechanisms could co-exist within single mineral due to the complex stress condition under triaxial compression test. The high uncertainty of failure process should be taken into account due to the complicated mineral composition and structure.
Radiography of geo-materials refers to visualize the interior information of natural geomaterials using rays, this information contains both the structural and functional details of the subjected samples. Radiography is a vital method to study compositions, structures, properties and functions, as well as a way to know geological phenomenon, process and dynamic causes. In this paper, techniques and corresponding applicable conditions of surface imaging, 3D interior structural imaging and in-situ structure imaging are studied. Structural and functional imaging of geo-materials are proposed based on the radiography fundamentals, conclusions of which are:(1) The techniques of structural imaging including visible ray imaging, infrared beams imaging, Electron beam imaging can be used image surface information. (2) X-rays, γ-rays and neutron rays can be used to image 3D structure due to their high energy. (3) Researches on static imaging such as particles, minerals, matrix and their spatial distribution tend to be mature and completed. In-situ imaging under temperature, pressure and pore pressure controls are the needed trends. It's an urgent demand to image the functional process of origin, enrichment, accumulation and seepage of geo-materials, but studies of which are still in an early stage. Radiography of geo-materials refers to visualize the interior information of natural geomaterials using rays, this information contains both the structural and functional details of the subjected samples. Radiography is a vital method to study compositions, structures, properties and functions, as well as a way to know geological phenomenon, process and dynamic causes. In this paper, techniques and corresponding applicable conditions of surface imaging, 3D interior structural imaging and in-situ structure imaging are studied. Structural and functional imaging of geo-materials are proposed based on the radiography fundamentals, conclusions of which are:(1) The techniques of structural imaging including visible ray imaging, infrared beams imaging, Electron beam imaging can be used image surface information. (2) X-rays, γ-rays and neutron rays can be used to image 3D structure due to their high energy. (3) Researches on static imaging such as particles, minerals, matrix and their spatial distribution tend to be mature and completed. In-situ imaging under temperature, pressure and pore pressure controls are the needed trends. It's an urgent demand to image the functional process of origin, enrichment, accumulation and seepage of geo-materials, but studies of which are still in an early stage.
Quarrying-induced collapse, an issue of particular concern in mining industry, is a typical form of man-made disaster. Identification of the morphological characteristics of such collapses is commonly based on seismic records. But comprehensive studies regarding the mechanism and energy conversion mode utilizing the seismic record are seldom undertaken. A huge collapse event occurred at the Biyutan mining cavern at Changyu Dongtian in Wenling city, China. It lasted for about 20 seconds and was observed and recorded on August 11, 1997. After the collapse, nearly 1.35×106 m3 of rock blocks were left on the floor and occupied an area of about 31 380 m2. the authors conducted a field survey on engineering geology, retrospectively analyzed the collapsing process through interviewing local residents and referring related documents, and identified the seismic records from surrounding seismic stations. The roof collapse is established at the Biyutan cavern that was excavated in massive tuff. The over excavation of several pillars substantially affected the stress field in cavern roof, which gave a rise to a local failure of the roof and then gradually developed into a widespread failure. During the collapse, outbursts of water and air shock waves resulted in loss of life and property within a distance of 150 m from the mine opening. The seismic records of Wenzhou Station 93 km south from the site revealed the collapse event, which is agreement with the energy transformation in site retrospective analysis on building failures and subject movement. This event reminds us that reasonable allocation of sufficiently strong safety pillars and installation of monitoring system are absolutely essential in underground quarrying operations to avoid overall failure and ensure the safety of the people nearby. Quarrying-induced collapse, an issue of particular concern in mining industry, is a typical form of man-made disaster. Identification of the morphological characteristics of such collapses is commonly based on seismic records. But comprehensive studies regarding the mechanism and energy conversion mode utilizing the seismic record are seldom undertaken. A huge collapse event occurred at the Biyutan mining cavern at Changyu Dongtian in Wenling city, China. It lasted for about 20 seconds and was observed and recorded on August 11, 1997. After the collapse, nearly 1.35×106 m3 of rock blocks were left on the floor and occupied an area of about 31 380 m2. the authors conducted a field survey on engineering geology, retrospectively analyzed the collapsing process through interviewing local residents and referring related documents, and identified the seismic records from surrounding seismic stations. The roof collapse is established at the Biyutan cavern that was excavated in massive tuff. The over excavation of several pillars substantially affected the stress field in cavern roof, which gave a rise to a local failure of the roof and then gradually developed into a widespread failure. During the collapse, outbursts of water and air shock waves resulted in loss of life and property within a distance of 150 m from the mine opening. The seismic records of Wenzhou Station 93 km south from the site revealed the collapse event, which is agreement with the energy transformation in site retrospective analysis on building failures and subject movement. This event reminds us that reasonable allocation of sufficiently strong safety pillars and installation of monitoring system are absolutely essential in underground quarrying operations to avoid overall failure and ensure the safety of the people nearby.
The solute and isotope profile of the unsaturated zone(UZ)in arid and semiarid areas, can not only provide groundwater recharge information, but also record the past climate and environment changes. Based on the last 10-year's study in the Ordos Basin(including the Loess Plateau in the south part and the desert plateau in the north part), we have combined evaluations of the thick UZ with those of the saturated zone and used multiple tracers to promote the potential of UZ in groundwater study in arid and semiarid areas, including reconstruction of groundwater recharge history, determination of groundwater recharge mechanism, assessment of impact of vegetation changes on groundwater recharge and evaluation of whole processes of groundwater pollution. the results show that shallow groundwater in arid and semiarid areas is often not in equilibrium with near-surface boundary conditions. This is especially the case where the unsaturated zone is thick and recharge rate is limited. A case study from west part of the desert plateau in the Ordos Basin shows that the present diffuse recharge beneath the grassland is 0.11-0.32 mm/year, based on the chloride mass balance of seven soil profiles. the chloride accumulation age is approximately 2, 500 years at a depth of 13 m in the unsaturated zone. the average Cl content in soil moisture in the upper 13 m of the unsaturated zone ranges from 2, 842 to 7, 856 mg·L-1, whereas the shallow groundwater Cl content ranges from 95 to 351 mg·L-1. the corrected 14C age of shallow groundwater ranges from 4, 327 to 29, 708 years. in typical tablelands in the Loess Plateau, the length of time required for annual precipitation to reach the water table ranges from decades of years to hundreds of years with soil moisture velocity of 0.1 to 0.3 m·a-1 and shallow groundwaters are all pre-modern water and paleowater, the Cl and NO3 contents in the upper UZ are considerably higher than those in the deep UZ and shallow groundwater because of recent human activities. the homogeneous material of the UZ and relatively old groundwater age imply that piston flow is the dominant recharge mechanism for the shallow groundwater in the tableland. The"Returning Farmland to Forest and Grassland" project in the Loess Plateau and plantations in desert areas have decreased groundwater recharge and increased solute content in UZ moisture, which can be used to quantitatively determine the changes in recharge rates. the paper has strengthened the role of the UZ in groundwater recharge study in arid and semiarid area, to which should be paid more attention in groundwater resources assessment and groundwater pollution investigation. The solute and isotope profile of the unsaturated zone(UZ)in arid and semiarid areas, can not only provide groundwater recharge information, but also record the past climate and environment changes. Based on the last 10-year's study in the Ordos Basin(including the Loess Plateau in the south part and the desert plateau in the north part), we have combined evaluations of the thick UZ with those of the saturated zone and used multiple tracers to promote the potential of UZ in groundwater study in arid and semiarid areas, including reconstruction of groundwater recharge history, determination of groundwater recharge mechanism, assessment of impact of vegetation changes on groundwater recharge and evaluation of whole processes of groundwater pollution. the results show that shallow groundwater in arid and semiarid areas is often not in equilibrium with near-surface boundary conditions. This is especially the case where the unsaturated zone is thick and recharge rate is limited. A case study from west part of the desert plateau in the Ordos Basin shows that the present diffuse recharge beneath the grassland is 0.11-0.32 mm/year, based on the chloride mass balance of seven soil profiles. the chloride accumulation age is approximately 2, 500 years at a depth of 13 m in the unsaturated zone. the average Cl content in soil moisture in the upper 13 m of the unsaturated zone ranges from 2, 842 to 7, 856 mg·L-1, whereas the shallow groundwater Cl content ranges from 95 to 351 mg·L-1. the corrected 14C age of shallow groundwater ranges from 4, 327 to 29, 708 years. in typical tablelands in the Loess Plateau, the length of time required for annual precipitation to reach the water table ranges from decades of years to hundreds of years with soil moisture velocity of 0.1 to 0.3 m·a-1 and shallow groundwaters are all pre-modern water and paleowater, the Cl and NO3 contents in the upper UZ are considerably higher than those in the deep UZ and shallow groundwater because of recent human activities. the homogeneous material of the UZ and relatively old groundwater age imply that piston flow is the dominant recharge mechanism for the shallow groundwater in the tableland. The"Returning Farmland to Forest and Grassland" project in the Loess Plateau and plantations in desert areas have decreased groundwater recharge and increased solute content in UZ moisture, which can be used to quantitatively determine the changes in recharge rates. the paper has strengthened the role of the UZ in groundwater recharge study in arid and semiarid area, to which should be paid more attention in groundwater resources assessment and groundwater pollution investigation.
The history and current research status of the internal stress in the residual stress of rock are reviewed and important meanings of research on the internal stress are pointed out in this paper. The basic characteristics of internal stress in rock are analyzed and the formation cause and mechanism are concluded and discussed. Based on analysis, we conclude that the elastic and plastic characteristics and inhomogeneous plastic deformation are necessary condition for locking internal stress of rock, and external loads. Physical and chemical effects and thermodynamic functions are the direct power to store internal stresses. Determining principle and measurement techniques of internal stress in rock are analyzed and summarized respectively. We believe that the plastic deformation is the fundamental cause for releasing of internal stress. Besides, internal stress in rock may affect mechanical behavior, to which attention should be pay. The history and current research status of the internal stress in the residual stress of rock are reviewed and important meanings of research on the internal stress are pointed out in this paper. The basic characteristics of internal stress in rock are analyzed and the formation cause and mechanism are concluded and discussed. Based on analysis, we conclude that the elastic and plastic characteristics and inhomogeneous plastic deformation are necessary condition for locking internal stress of rock, and external loads. Physical and chemical effects and thermodynamic functions are the direct power to store internal stresses. Determining principle and measurement techniques of internal stress in rock are analyzed and summarized respectively. We believe that the plastic deformation is the fundamental cause for releasing of internal stress. Besides, internal stress in rock may affect mechanical behavior, to which attention should be pay.
In the recent two decades, the authors have investigated many large underground caverns in Zhejiang, Anhui and other places in China, including more than 3 000 ancient man-made rock caverns. Through field investigations, it is found that Tiantai Heidong underground rock caverns have the largest span of 92 m, Changyudongtian caverns have the maximum height of 99 m, as well as the most exquisite chisel imprints on sidewalls in Longyou Grottoes. These caverns have the same characteristics including excavated a few hundred years to several thousand years ago, have maintained the stability of thousands of years. These caverns have their own unique structures including inclined walls, fishtail-shaped pillars, inclined roof, dome, rib-shaped arch, thin common sidewall and horizontal partition between two caverns. Research results show that these unique structures play a crucial role in the long-term stability of the caverns. In addition, there are also many high-level technologies in the ancient large underground caverns such as the measurement technology, excavation technology and waterproof technology. These groups of unsupported large-span artificial caverns, which have been maintained for more than a thousand years, provide some enlightenments of the long-term strength, the water effect on surrounding rock and the evaluation of blasting damage. However, with the discovery of these caverns and the development of tourism, various kinds of deformations and failures have been produced, posing a serious threat to the stability and security of these ancient rock cavern relics. At the same time, some new topics and challenges have been proposed for the long-term protection of large-span artificial rock caverns. In the recent two decades, the authors have investigated many large underground caverns in Zhejiang, Anhui and other places in China, including more than 3 000 ancient man-made rock caverns. Through field investigations, it is found that Tiantai Heidong underground rock caverns have the largest span of 92 m, Changyudongtian caverns have the maximum height of 99 m, as well as the most exquisite chisel imprints on sidewalls in Longyou Grottoes. These caverns have the same characteristics including excavated a few hundred years to several thousand years ago, have maintained the stability of thousands of years. These caverns have their own unique structures including inclined walls, fishtail-shaped pillars, inclined roof, dome, rib-shaped arch, thin common sidewall and horizontal partition between two caverns. Research results show that these unique structures play a crucial role in the long-term stability of the caverns. In addition, there are also many high-level technologies in the ancient large underground caverns such as the measurement technology, excavation technology and waterproof technology. These groups of unsupported large-span artificial caverns, which have been maintained for more than a thousand years, provide some enlightenments of the long-term strength, the water effect on surrounding rock and the evaluation of blasting damage. However, with the discovery of these caverns and the development of tourism, various kinds of deformations and failures have been produced, posing a serious threat to the stability and security of these ancient rock cavern relics. At the same time, some new topics and challenges have been proposed for the long-term protection of large-span artificial rock caverns.
In macroscopic scale, en echelon intermittent fractures are common in nature and in engineering rocks. Nevertheless, do these en echelon intermittent fractures still occur in micro-nano scale? What is the specific process of crack growth and evolution? This is a basic scientific problem for rock mechanics. Using the arch specimens of shale with a notch on the arch boundary, in-situ tension and crack growth observation are conducted under a scanning electron microscope(SEM). from the in-situ SEM observations, we learn that:(1)En echelon intermittent cracks still can be observed in micro-nano scale with a "S" or reversed "S" shape. They are induced by combined actions of complex tension-shear stress field ahead of the crack tip and the mineral anisotropy.(2)the arrangements, growth and evolution process of these en echelon intermittent cracks generally follow a certain regularity. the adjacent intermittent cracks are approximately parallel to each other. for each single crack, the intermediate tensile crack is parallel to the maximum tension stress, and the wing cracks at both ends tend to grow towards the maximum shear stress.(3)En echelon intermittent cracks in micro-nano scale only represent a transient state of shearing deformation or an intermediate growth stage of the main crack.(4)There exists a hierarchical structure among some en echelon intermittent cracks in micro-nano scale. the en echelon intermittent cracks in relatively large scale are included in those in relatively small scale. This paper provides observation evidence for en echelon intermittent cracks, which contributes for analysis on the evolution process of multi-scale cracks. In macroscopic scale, en echelon intermittent fractures are common in nature and in engineering rocks. Nevertheless, do these en echelon intermittent fractures still occur in micro-nano scale? What is the specific process of crack growth and evolution? This is a basic scientific problem for rock mechanics. Using the arch specimens of shale with a notch on the arch boundary, in-situ tension and crack growth observation are conducted under a scanning electron microscope(SEM). from the in-situ SEM observations, we learn that:(1)En echelon intermittent cracks still can be observed in micro-nano scale with a "S" or reversed "S" shape. They are induced by combined actions of complex tension-shear stress field ahead of the crack tip and the mineral anisotropy.(2)the arrangements, growth and evolution process of these en echelon intermittent cracks generally follow a certain regularity. the adjacent intermittent cracks are approximately parallel to each other. for each single crack, the intermediate tensile crack is parallel to the maximum tension stress, and the wing cracks at both ends tend to grow towards the maximum shear stress.(3)En echelon intermittent cracks in micro-nano scale only represent a transient state of shearing deformation or an intermediate growth stage of the main crack.(4)There exists a hierarchical structure among some en echelon intermittent cracks in micro-nano scale. the en echelon intermittent cracks in relatively large scale are included in those in relatively small scale. This paper provides observation evidence for en echelon intermittent cracks, which contributes for analysis on the evolution process of multi-scale cracks.
At medium and low confining stress of triaxial and uniaxial compressive load, five stages as being (1)crack closure, (2)linear elastic deformation, (3)crack initiation and stable crack growth, (4)critical energy release and unstable crack growth, and (5)failure and post peak behavior can be defined for brittle rock material. Direct observation on the surface of flaw contained specimens, indirect observation techniques such as strain monitoring, Acoustic emission(AE)monitoring, acoustic wave velocity monitoring, computerized tomography scanning, microscopic observation(SEM/ESEM)etc, . Under the compressive load, tensile cracks are the first and primary cracks, which propagate generally along the loading direction. A continuing measure method for acoustic wave velocity measurement during cracking processes of rock was proposed based the discipline of crack propagation. The method will benefit for the indirect observation of cracking processes by monitoring the changes of acoustic wave velocity. At medium and low confining stress of triaxial and uniaxial compressive load, five stages as being (1)crack closure, (2)linear elastic deformation, (3)crack initiation and stable crack growth, (4)critical energy release and unstable crack growth, and (5)failure and post peak behavior can be defined for brittle rock material. Direct observation on the surface of flaw contained specimens, indirect observation techniques such as strain monitoring, Acoustic emission(AE)monitoring, acoustic wave velocity monitoring, computerized tomography scanning, microscopic observation(SEM/ESEM)etc, . Under the compressive load, tensile cracks are the first and primary cracks, which propagate generally along the loading direction. A continuing measure method for acoustic wave velocity measurement during cracking processes of rock was proposed based the discipline of crack propagation. The method will benefit for the indirect observation of cracking processes by monitoring the changes of acoustic wave velocity.
This papter uses the compaction method for preparing the remolded red clay with the addition of nano graphite powder(NGP). It designs the consolidation and undrained triaxial experiment of different dosage of NGP under optimum water content of red clay. The effect of doped with different amount of nano graphite powder on mechanical properties of red clay is analyzed by adopting the method of stress and strain curve, which obtains the rules of shear strength and shear strength index. The improving mechanism is futher analyzed with SEM method. The experimental results show that:with the increase of NGP content, the shear strength and cohesion C increase firstly and then decrease, the internal friction angle \begin{document}$\varphi $\end{document} remains basically unchanged. It can be observed that the appropriate amount of NGP has an significantly improvement on the mechanical properties of red clay. The best dosage is between 1% to 2%. The study suggests that the presenting mechanical properties of NGP-red clay is closely related to the effect of the NGP on the pore structure of red clay and the particle adhesion and cementation. This papter uses the compaction method for preparing the remolded red clay with the addition of nano graphite powder(NGP). It designs the consolidation and undrained triaxial experiment of different dosage of NGP under optimum water content of red clay. The effect of doped with different amount of nano graphite powder on mechanical properties of red clay is analyzed by adopting the method of stress and strain curve, which obtains the rules of shear strength and shear strength index. The improving mechanism is futher analyzed with SEM method. The experimental results show that:with the increase of NGP content, the shear strength and cohesion C increase firstly and then decrease, the internal friction angle \begin{document}$\varphi $\end{document} remains basically unchanged. It can be observed that the appropriate amount of NGP has an significantly improvement on the mechanical properties of red clay. The best dosage is between 1% to 2%. The study suggests that the presenting mechanical properties of NGP-red clay is closely related to the effect of the NGP on the pore structure of red clay and the particle adhesion and cementation.
Slurry shield tunnel construction produces a large amount of waste mud. If these engineering muds cannot be properly disposed, they probably bring environmental pollution, occupation of land and other issues, highly disturbing the normal operation of cities. The waste mud in this experiment is collected in the construction site of tunnel projects in Xiamen. In order to dispose the waste mud safely and effectively, chemical solidification technology is used to achieve the optimal curing effect through comparative tests. In these tests, different values of curing agent type, agent mixing ratio, and mud initial water content lead to different values of compressive strength, pH value, and water content of modified-curing mud samples. The optimum curing agent type, agent mixing ratio and initial water content of waste mud are obtained with the analysis of curing mechanism and related data. These tests are divided into 3 parts. The first part is curing agent types comparative test, which includes 425# ordinary Portland cement(S1), CERSM mud curing agent Ⅰ(C1), CERSM mud curing agent Ⅱ(C2) and quick lime(L1). The second part is curing agent mixing ratio comparative test, which includes 3%, 5%, 7%, 10%, 15% agent mixing ratio. The last part is mud initial water content comparative test, which includes 100%, 125%, 150%, 180% mud initial water content. Then the optimum curing agent type, mixing ratio and initial water content of slurry are obtained respectively by testing the effects of different factors(agent types, agent ratio and mud initial water content) on compressive strength, pH value, and water content of modified-curing mud samples. Based on the compressive strength, sample water content and pH value of the above three aspects, the curing effect of curing agent from high to low is ranked as CERSM mud curing agent Ⅱ(C2), 425# ordinary Portland cement(S1), CERSM mud curing agent Ⅰ(C1) and quick lime(L1) from highest to the lowest. Compressive strength increases with the increase of the curing agent ratio, sample water content decreases with the curing agent ratio increasing, and pH value increases with the increase of the curing agent ratio, decreases with age. Compressive strength decreases with the increase of mud initial water content, sample water content increases with the increase of mud initial water content, and the pH of the modified-curing mud sample has nothing to do with mud initial water content. In engineering, CERSM mud curing agent Ⅱ, 10% ratio, and 100% mud initial water content are finally chosen. The compressive strength of modified-curing mud sample after 28 d is up to 1.5 MPa, which is 4 times of the strength of ordinary cement solidified slurry sample. Moreover, as the growth of the age, the shear strength of modified-curing mud sample has a substantial increase, the cohesion of sample increases to 262 kPa, and internal friction angle increases to 38.65°, and modified-curing mud can be used as building filler. The presented technology can be used to dispose waste mud, which can not only solve the environmental pollution problem, but also help to realize the resource utilization of the waste mud. Slurry shield tunnel construction produces a large amount of waste mud. If these engineering muds cannot be properly disposed, they probably bring environmental pollution, occupation of land and other issues, highly disturbing the normal operation of cities. The waste mud in this experiment is collected in the construction site of tunnel projects in Xiamen. In order to dispose the waste mud safely and effectively, chemical solidification technology is used to achieve the optimal curing effect through comparative tests. In these tests, different values of curing agent type, agent mixing ratio, and mud initial water content lead to different values of compressive strength, pH value, and water content of modified-curing mud samples. The optimum curing agent type, agent mixing ratio and initial water content of waste mud are obtained with the analysis of curing mechanism and related data. These tests are divided into 3 parts. The first part is curing agent types comparative test, which includes 425# ordinary Portland cement(S1), CERSM mud curing agent Ⅰ(C1), CERSM mud curing agent Ⅱ(C2) and quick lime(L1). The second part is curing agent mixing ratio comparative test, which includes 3%, 5%, 7%, 10%, 15% agent mixing ratio. The last part is mud initial water content comparative test, which includes 100%, 125%, 150%, 180% mud initial water content. Then the optimum curing agent type, mixing ratio and initial water content of slurry are obtained respectively by testing the effects of different factors(agent types, agent ratio and mud initial water content) on compressive strength, pH value, and water content of modified-curing mud samples. Based on the compressive strength, sample water content and pH value of the above three aspects, the curing effect of curing agent from high to low is ranked as CERSM mud curing agent Ⅱ(C2), 425# ordinary Portland cement(S1), CERSM mud curing agent Ⅰ(C1) and quick lime(L1) from highest to the lowest. Compressive strength increases with the increase of the curing agent ratio, sample water content decreases with the curing agent ratio increasing, and pH value increases with the increase of the curing agent ratio, decreases with age. Compressive strength decreases with the increase of mud initial water content, sample water content increases with the increase of mud initial water content, and the pH of the modified-curing mud sample has nothing to do with mud initial water content. In engineering, CERSM mud curing agent Ⅱ, 10% ratio, and 100% mud initial water content are finally chosen. The compressive strength of modified-curing mud sample after 28 d is up to 1.5 MPa, which is 4 times of the strength of ordinary cement solidified slurry sample. Moreover, as the growth of the age, the shear strength of modified-curing mud sample has a substantial increase, the cohesion of sample increases to 262 kPa, and internal friction angle increases to 38.65°, and modified-curing mud can be used as building filler. The presented technology can be used to dispose waste mud, which can not only solve the environmental pollution problem, but also help to realize the resource utilization of the waste mud.
Expansive soil is considered as a problematic soil in engineering, because it usually results in various engineering geological problems and disasters. According to the published results on the engineering geological characteristics of expansive soil in recent years, the advances on swelling-shrinkage behavior, desiccation cracking, overconsolidation, strength, permeability and microstructure of expansive soil were summarized, and the following main knowledge was obtained. (1)The swelling-shrinking characteristics are mainly related to the fraction of expansive clay minerals, hydro-mechanical boundary conditions and initial state. Irreversible volumetric deformation would occur when the expansive soil is subjected to wetting-drying cycles. Until now, there is still not a uniform viewpoint on the intrinsic mechanism on swelling-shrinking behavior. (2)Desiccation cracking is one of the salient features to distinguish expansive soil from other soils. The presence of cracks in soil can significantly undermine the overall structure of the soil, greatly weaken the mechanical properties and lead to many engineering geological problems directly or indirectly. The formation of desiccation cracks is related to expansive soil mineral composition, microstructure and the development of internal stress during drying. (3)Overconsolidation makes expansive soil has a greater structural strength and horizontal stress. Stress-release cracks are easy to occur when the expansive soil slope is excavated, which can damage the overall structure of the soil and promote landslide.(4)In terms of strength, most of studies focused on the effect of wetting-drying cycles. Generally, the strength decreases gradually with increasing wetting-drying cycles and eventually reaches stabilization. The wetting-drying cycle induced presence of cracks and microstructure arrangement are the two factors responsible for the corresponding strength changes. (5)The hydraulic conductivity is largely controlled by cracks. It is therefore important to consider the crack effect when performing permeability test in laboratory.(6)Microstructure of the expansive soil reflects the formation conditions and stress history. It is a fundamental factor controlling the macro-physical and mechanical behavior. Microstructure analysis is also the important way and theoretical basis to explore the intrinsic mechanisms of the observed macroscopic properties. Furthermore, as for as expansive soil engineering treatment technology, this article focused on the physical treatment technology for embankment filled with expansive soil and flexible supporting technology for expansive soil cut slope. Based on the above understanding and current research shortages in this field, some important research topics that should be well investigated in future were proposed, including anisotropic behavior of swelling-shrinking, mechanism of the desiccation cracking, quantitative relationship between geometrical parameters of cracks and the indicators of macro engineering properties, the coupling of macro-micro mechanical model and the hydro-mechanical response characteristics of expansive soil under multi-field coupling condition, et al. Expansive soil is considered as a problematic soil in engineering, because it usually results in various engineering geological problems and disasters. According to the published results on the engineering geological characteristics of expansive soil in recent years, the advances on swelling-shrinkage behavior, desiccation cracking, overconsolidation, strength, permeability and microstructure of expansive soil were summarized, and the following main knowledge was obtained. (1)The swelling-shrinking characteristics are mainly related to the fraction of expansive clay minerals, hydro-mechanical boundary conditions and initial state. Irreversible volumetric deformation would occur when the expansive soil is subjected to wetting-drying cycles. Until now, there is still not a uniform viewpoint on the intrinsic mechanism on swelling-shrinking behavior. (2)Desiccation cracking is one of the salient features to distinguish expansive soil from other soils. The presence of cracks in soil can significantly undermine the overall structure of the soil, greatly weaken the mechanical properties and lead to many engineering geological problems directly or indirectly. The formation of desiccation cracks is related to expansive soil mineral composition, microstructure and the development of internal stress during drying. (3)Overconsolidation makes expansive soil has a greater structural strength and horizontal stress. Stress-release cracks are easy to occur when the expansive soil slope is excavated, which can damage the overall structure of the soil and promote landslide.(4)In terms of strength, most of studies focused on the effect of wetting-drying cycles. Generally, the strength decreases gradually with increasing wetting-drying cycles and eventually reaches stabilization. The wetting-drying cycle induced presence of cracks and microstructure arrangement are the two factors responsible for the corresponding strength changes. (5)The hydraulic conductivity is largely controlled by cracks. It is therefore important to consider the crack effect when performing permeability test in laboratory.(6)Microstructure of the expansive soil reflects the formation conditions and stress history. It is a fundamental factor controlling the macro-physical and mechanical behavior. Microstructure analysis is also the important way and theoretical basis to explore the intrinsic mechanisms of the observed macroscopic properties. Furthermore, as for as expansive soil engineering treatment technology, this article focused on the physical treatment technology for embankment filled with expansive soil and flexible supporting technology for expansive soil cut slope. Based on the above understanding and current research shortages in this field, some important research topics that should be well investigated in future were proposed, including anisotropic behavior of swelling-shrinking, mechanism of the desiccation cracking, quantitative relationship between geometrical parameters of cracks and the indicators of macro engineering properties, the coupling of macro-micro mechanical model and the hydro-mechanical response characteristics of expansive soil under multi-field coupling condition, et al.
Huangtupo landslide, geologically one of the most complicated landslides in the Three Gorges Reservoir area, attracted much attention for being the old site of Badong county. To reveal the true condition of the spatial distribution, mechanical behavior and deformation properties of slip zone in Sub-landslide 1#, the major and controlling part of Huangtupo landslide, a large-scale investigation tunnel group, combined with boreholes, tests and in-situ monitoring are applied to study the spatial distribution, thickness, formation, physical properties and deformation rules of slip zone. Relatively systematic and comprehensive innovations are obtained during the study. The results show that there are two slip zones in the upper and lower part of Sub-landsldie 1#. The major lower slip zone is located at the eastern part of Sub-landsldie 1#, with the elevation decreasing along the main sliding direction. The elevation is lower in the middle and higher in the eastern part. In addition, the spatial distribution of strength parameters show the trend of increasing along the main sliding direction from the edge to front part. The trend also shows in the content change of clay and silt particles along the main sliding direction. As to the deformation distribution, the slip zone at the landslide toe creep slower than the middle edge part of landslide. The deformation response shows spatial svariation to the external influencing factor water level and rainfall. Huangtupo landslide, geologically one of the most complicated landslides in the Three Gorges Reservoir area, attracted much attention for being the old site of Badong county. To reveal the true condition of the spatial distribution, mechanical behavior and deformation properties of slip zone in Sub-landslide 1#, the major and controlling part of Huangtupo landslide, a large-scale investigation tunnel group, combined with boreholes, tests and in-situ monitoring are applied to study the spatial distribution, thickness, formation, physical properties and deformation rules of slip zone. Relatively systematic and comprehensive innovations are obtained during the study. The results show that there are two slip zones in the upper and lower part of Sub-landsldie 1#. The major lower slip zone is located at the eastern part of Sub-landsldie 1#, with the elevation decreasing along the main sliding direction. The elevation is lower in the middle and higher in the eastern part. In addition, the spatial distribution of strength parameters show the trend of increasing along the main sliding direction from the edge to front part. The trend also shows in the content change of clay and silt particles along the main sliding direction. As to the deformation distribution, the slip zone at the landslide toe creep slower than the middle edge part of landslide. The deformation response shows spatial svariation to the external influencing factor water level and rainfall.
The strictest criteria for shallow electrical exploration method are up to the world level, because the criteria and measurement to develop of Xiong-An new area is laid down by China. Therefore, this paper sums up and compares two electrical methods. They are the high density resistivity method and the Multi-Channel powered electric system. Both are developed by Chinese Academy of Sciences. Both are expected to be used in the development of Xiong-An new area. The two methods can get higher horizontal resolution data than those obtained by other electric methods due to the similar configuration as the reflect seismic method. That is, laying down all of the electrodes along the survey at the same time, and collecting density data from shallow to deep through moving the transmitter. Therefore, the integral of these two electric methods can achieve fine electrical detection, and can provide high vertical resolution geophysical data for the hydrology and geology exploration task in developing Xiong-An new area. The strictest criteria for shallow electrical exploration method are up to the world level, because the criteria and measurement to develop of Xiong-An new area is laid down by China. Therefore, this paper sums up and compares two electrical methods. They are the high density resistivity method and the Multi-Channel powered electric system. Both are developed by Chinese Academy of Sciences. Both are expected to be used in the development of Xiong-An new area. The two methods can get higher horizontal resolution data than those obtained by other electric methods due to the similar configuration as the reflect seismic method. That is, laying down all of the electrodes along the survey at the same time, and collecting density data from shallow to deep through moving the transmitter. Therefore, the integral of these two electric methods can achieve fine electrical detection, and can provide high vertical resolution geophysical data for the hydrology and geology exploration task in developing Xiong-An new area.
The overlying rock mass deformation induced by mining is complex mechanical issue in metal mine because of its complicated conditions. Mining operations could change original stresses distribution of surrounding rock, that lead to stresses redistribution of overlying rock then reach a new balance. Structural planes have some influence on overlying rock deformation and failure when they developed and connected. for this situation, we built a 2-dimension discrete element method model utilized in Udec, and analyzed break characteristics and mechanisms of 2-rock-bridge and 4-rock-bridge. We also conducted some comparative studies of stress relief regulation in roof rock. We chose three experimental groups, which joint conditions are 0°/90°, 45°/45°, 20°/70°respectively, to analyze deformation mechanism of rock mass movement. by numerical simulation experiment, we demonstrated the ground movement characteristic and subsidence region. the experimental results have consistency with monitoring data of surface subsidence by GPS. The overlying rock mass deformation induced by mining is complex mechanical issue in metal mine because of its complicated conditions. Mining operations could change original stresses distribution of surrounding rock, that lead to stresses redistribution of overlying rock then reach a new balance. Structural planes have some influence on overlying rock deformation and failure when they developed and connected. for this situation, we built a 2-dimension discrete element method model utilized in Udec, and analyzed break characteristics and mechanisms of 2-rock-bridge and 4-rock-bridge. We also conducted some comparative studies of stress relief regulation in roof rock. We chose three experimental groups, which joint conditions are 0°/90°, 45°/45°, 20°/70°respectively, to analyze deformation mechanism of rock mass movement. by numerical simulation experiment, we demonstrated the ground movement characteristic and subsidence region. the experimental results have consistency with monitoring data of surface subsidence by GPS.
When a tension crack appears in a slope, it usually indicates the slope is reaching limited equilibrium and a landslide is most likely to occur. With a rainfall, pressure by the filling water in the tension crack becomes a triggering factor for the slope failure. Therefore the crack depth is one of the important factors in slope stability analysis since it determines the water pressure in the tension crack. This paper presents a potential triangle block model created by a tension crack in the upper slope. The crack depth equation is derived by the force balance. The angle of the sliding surface associated to angle of international friction at the tension crack is obtained by the inflection principle. The crack depth coefficient is calculated afterward. The analytical solution curves are prepared for practical determination of crack depth coefficients. The conditions for generation of a tension crack are identified as follows:the angle of the sliding surface at the tension crack should be smaller than the angle corresponding to the angle of internal friction determined by the limited values of the first degree derivative. The crack location formula are also given for both circular failure and non-circular failure slopes. The results are compared with the Spencer Method, proving potential for its applications in slope engineering. When a tension crack appears in a slope, it usually indicates the slope is reaching limited equilibrium and a landslide is most likely to occur. With a rainfall, pressure by the filling water in the tension crack becomes a triggering factor for the slope failure. Therefore the crack depth is one of the important factors in slope stability analysis since it determines the water pressure in the tension crack. This paper presents a potential triangle block model created by a tension crack in the upper slope. The crack depth equation is derived by the force balance. The angle of the sliding surface associated to angle of international friction at the tension crack is obtained by the inflection principle. The crack depth coefficient is calculated afterward. The analytical solution curves are prepared for practical determination of crack depth coefficients. The conditions for generation of a tension crack are identified as follows:the angle of the sliding surface at the tension crack should be smaller than the angle corresponding to the angle of internal friction determined by the limited values of the first degree derivative. The crack location formula are also given for both circular failure and non-circular failure slopes. The results are compared with the Spencer Method, proving potential for its applications in slope engineering.
Reticulate red clay is widely distributed in southern China area and common in many kinds of geotechnical engineering. At present, the research of the reticulate red clay mainly focused on the causes and granularity characteristics. The study on its unsaturated characteristics is relatively limited. In this paper, the filter paper method is applied to measure the matrix suction of reticulate red clay in different saturation conditions. Van Genuchten model is used to get the soil-water characteristic curve in drying-wetting process. It is found that due to the small and relatively uniform void, the air entry value of reticulate red clay(about 100 kPa) is relatively larger than that of normal clays. There is no obvious residual stage in its soil-water characteristic curve. The soil water characteristic curve is applied to analyze the stability of one dimensional infinite slope in drying and wetting process. The results indicate that in the same saturation, the slope is more stable in the drying process than in the wetting process. With the increase of depth and saturation, the difference of stability factor in the two processes tends to decrease. Due to the larger contribution of matrix suction, reticulate red clay slope is relatively stable. Reticulate red clay is widely distributed in southern China area and common in many kinds of geotechnical engineering. At present, the research of the reticulate red clay mainly focused on the causes and granularity characteristics. The study on its unsaturated characteristics is relatively limited. In this paper, the filter paper method is applied to measure the matrix suction of reticulate red clay in different saturation conditions. Van Genuchten model is used to get the soil-water characteristic curve in drying-wetting process. It is found that due to the small and relatively uniform void, the air entry value of reticulate red clay(about 100 kPa) is relatively larger than that of normal clays. There is no obvious residual stage in its soil-water characteristic curve. The soil water characteristic curve is applied to analyze the stability of one dimensional infinite slope in drying and wetting process. The results indicate that in the same saturation, the slope is more stable in the drying process than in the wetting process. With the increase of depth and saturation, the difference of stability factor in the two processes tends to decrease. Due to the larger contribution of matrix suction, reticulate red clay slope is relatively stable.
With the strategies of "One Belt One Road" and "Global Energy Interconnection" structuring and implementing, more and more power transmission and transformation projects are built on the complicated geological conditions in mountainous areas. However, current studies on the identification, prediction and evaluation approaches of rock collapse(rockfall) for power transmission and transformation projects are few. Therefore, it is difficult to effectively solve the increased translations between frequent occurrence of rock collapse(rockfall) and safety of construction and operation of power transmission and transformation projects in mountainous areas. For this reason, we studied the approach of rock collapse(rockfall) identification and prediction for power transmission and transformation project in mountain area, using remote sensing, UAV aerial photogrammetry, rock mass structure analysis tool and rockfall simulation method. Following conclusions were obtained:(1)Based on the thinking and approach of engineering geological zoning on large area-remote sensing analysis on medium area-UAV aerial photogrammetry on mountain area-analysis of rock structure characteristics, dangerous rock mass that will lead to rock collapse(rockfall) in long and large region of power transmission and transformation project could be identified quickly and analyzed. (2)Three-dimensional numerical simulation method could be used to quickly identify the characteristics of rockfall's arriving to the tower(electric substation) or not, and the kinematic characteristics of rockfall that will arrive to the tower(electric substation) could be analyzed carefully by integrating different approaches.(3)Approach of rockfall risk analysis for power transmission and transformation project. With the strategies of "One Belt One Road" and "Global Energy Interconnection" structuring and implementing, more and more power transmission and transformation projects are built on the complicated geological conditions in mountainous areas. However, current studies on the identification, prediction and evaluation approaches of rock collapse(rockfall) for power transmission and transformation projects are few. Therefore, it is difficult to effectively solve the increased translations between frequent occurrence of rock collapse(rockfall) and safety of construction and operation of power transmission and transformation projects in mountainous areas. For this reason, we studied the approach of rock collapse(rockfall) identification and prediction for power transmission and transformation project in mountain area, using remote sensing, UAV aerial photogrammetry, rock mass structure analysis tool and rockfall simulation method. Following conclusions were obtained:(1)Based on the thinking and approach of engineering geological zoning on large area-remote sensing analysis on medium area-UAV aerial photogrammetry on mountain area-analysis of rock structure characteristics, dangerous rock mass that will lead to rock collapse(rockfall) in long and large region of power transmission and transformation project could be identified quickly and analyzed. (2)Three-dimensional numerical simulation method could be used to quickly identify the characteristics of rockfall's arriving to the tower(electric substation) or not, and the kinematic characteristics of rockfall that will arrive to the tower(electric substation) could be analyzed carefully by integrating different approaches.(3)Approach of rockfall risk analysis for power transmission and transformation project.
The slope, whose stability is controlled by the locked segments within a potential slip surface, is referred to as the locked-segment type slope. It is well known that the instability prediction of slopes is a worldwide scientific problem. We suggest here that solving the instability prediction of the locked-segment type slope can be taken as a breakthrough because it has the explicit instability mechanism. In the present study, the classification method of locked-segment type slopes is discussed. It is pointed out that there exists an essential connection between three-phase creep development of the locked-segment type slope and the damage process of the locked segment, and that a locked-segment type slope will evolve into the tertiary creep stage when the cumulative damage of the locked segment reaches its volume dilation point. It is found that the peak strength point and the residual strength point of the locked segment can be regarded as two characteristic catastrophe points, respectively corresponding to the occurrence of the abrupt landslide and progressive one. Combining a one-dimensional renormalization group model with the strain-softening constitutive model of the locked segment, we establish the mechanical expressions among the volume dilation point, the peak strength point and the residual strength point and hence present a physical instability prediction model of locked-segment type slopes. The evolutionary mechanisms of three typical cases, the Yanchihe avalanche, the Xintan landslide and the wedge rockslide on the left abutment of Libby Dam, are reasonably explained and satisfied retrospective analysis results are obtained by the model. Finally, some related supporting techniques and applying principles about the model are introduced for actual applications. The slope, whose stability is controlled by the locked segments within a potential slip surface, is referred to as the locked-segment type slope. It is well known that the instability prediction of slopes is a worldwide scientific problem. We suggest here that solving the instability prediction of the locked-segment type slope can be taken as a breakthrough because it has the explicit instability mechanism. In the present study, the classification method of locked-segment type slopes is discussed. It is pointed out that there exists an essential connection between three-phase creep development of the locked-segment type slope and the damage process of the locked segment, and that a locked-segment type slope will evolve into the tertiary creep stage when the cumulative damage of the locked segment reaches its volume dilation point. It is found that the peak strength point and the residual strength point of the locked segment can be regarded as two characteristic catastrophe points, respectively corresponding to the occurrence of the abrupt landslide and progressive one. Combining a one-dimensional renormalization group model with the strain-softening constitutive model of the locked segment, we establish the mechanical expressions among the volume dilation point, the peak strength point and the residual strength point and hence present a physical instability prediction model of locked-segment type slopes. The evolutionary mechanisms of three typical cases, the Yanchihe avalanche, the Xintan landslide and the wedge rockslide on the left abutment of Libby Dam, are reasonably explained and satisfied retrospective analysis results are obtained by the model. Finally, some related supporting techniques and applying principles about the model are introduced for actual applications.
This paper raises the concept of Landslide Seismology Geology, which belongs to the field of Environmental Earth Sciences. This sub-discipline is concerned with the mechanism, distribution and evolution of landslides triggered by earthquakes; and also is a subject that addresses issues in earthquake geology using information from earthquake-triggered landslides. It can also be regarded as a cross-discipline among Disaster Geology, Earthquake Geology and Engineering Geology(or Geotechnical Geology). It is related to many disciplines or technologies, such as Solid Geophysics, Tectonics, Tectonic Geomorphology, Environmental Geology, Numerical Computation, Geographic Information System(GIS), Remote Sensing, and Statistical Analysis. This paper outlines the research framework and system of the Landslide Seismology Geology from scientific research and practical application. The purpose of its scientific research is to explore the laws of earthquake-triggered landslides, while the practical application is aimed to serve landslide hazard prevention and mitigation. According to these goals, the research contents are generally divided into two aspects:(1)Studying mechanisms, distribution patterns and evolution laws of earthquake-triggered landslides; (2)Establishing relationships of earthquake-triggered landslides with earthquakes, seismogenic faults and earthquake ruptures. Then employing these relationships to solve problems of earthquake geology, such as seismology(seismic parameters, ground shaking, and seismic intensity), seismogenic faults(geometry, kinematics, and rupture processes), and geology(geomorphologic evolution). Finally, this paper overviews some aspects of this sub-discipline, including database of earthquake-triggered landslides, case analysis of earthquake-triggered landslides based on events around the world, the relationship between earthquake-triggered landslides and earthquake geology objects, and evolution law of earthquake-triggered landslides. In short, taking into account the development of the remote sensing and GIS technologies, increasingly urgent needs of earthquake-triggered landslide disaster prevention and mitigation, and the tendency of multi-disciplinary integration, the geology of earthquake landslides will receive increasing attentions in the community of geosciences. This paper raises the concept of Landslide Seismology Geology, which belongs to the field of Environmental Earth Sciences. This sub-discipline is concerned with the mechanism, distribution and evolution of landslides triggered by earthquakes; and also is a subject that addresses issues in earthquake geology using information from earthquake-triggered landslides. It can also be regarded as a cross-discipline among Disaster Geology, Earthquake Geology and Engineering Geology(or Geotechnical Geology). It is related to many disciplines or technologies, such as Solid Geophysics, Tectonics, Tectonic Geomorphology, Environmental Geology, Numerical Computation, Geographic Information System(GIS), Remote Sensing, and Statistical Analysis. This paper outlines the research framework and system of the Landslide Seismology Geology from scientific research and practical application. The purpose of its scientific research is to explore the laws of earthquake-triggered landslides, while the practical application is aimed to serve landslide hazard prevention and mitigation. According to these goals, the research contents are generally divided into two aspects:(1)Studying mechanisms, distribution patterns and evolution laws of earthquake-triggered landslides; (2)Establishing relationships of earthquake-triggered landslides with earthquakes, seismogenic faults and earthquake ruptures. Then employing these relationships to solve problems of earthquake geology, such as seismology(seismic parameters, ground shaking, and seismic intensity), seismogenic faults(geometry, kinematics, and rupture processes), and geology(geomorphologic evolution). Finally, this paper overviews some aspects of this sub-discipline, including database of earthquake-triggered landslides, case analysis of earthquake-triggered landslides based on events around the world, the relationship between earthquake-triggered landslides and earthquake geology objects, and evolution law of earthquake-triggered landslides. In short, taking into account the development of the remote sensing and GIS technologies, increasingly urgent needs of earthquake-triggered landslide disaster prevention and mitigation, and the tendency of multi-disciplinary integration, the geology of earthquake landslides will receive increasing attentions in the community of geosciences.
A large scale of mountain rock avalanche occurred in Pusa village, Zhangjiawan town, Nayong county, Guizhou Province at about 10:30 on August 28, 2017. The rock mass with the volume of 49.1×104 m3 moved down and scraped the original loose deposits and finally formed deposits of 82.3×104 m3, which destroyed parts of Pusa village, resulted in the death of 26 persons and missing of 9 persons. Based on site investigation, unmanned aerial vehicle(UAV)photography and ground based synthetic aperture radar(GBSAR)monitoring and other technologies, this paper provides a detailed description on the characteristics and a comprehensive analysis on the dynamic process and failure mechanism of the rock avalanche. The preliminary study suggested that the rock masses of the source area were shattered due to the underground mining activities. The shattered rock masses suffered long-term effects of gravity, which eventually resulted the failure of the rock masses. The movement of the rock avalanche lasted for 7 minutes and 21 seconds in which the main rock masses failure lasted for only 26 seconds with the long runout of 788 m and the maximum speed of 43.83 m·s-1, belonging to typical high speed and long runout rock avalanche. There will be a big attribution if such case can be studied further. It can provide the significant experience on dealing with this kind of rock masses failure and how to provide advice on early warning and remediation project on similar cases in southwestern mountain areas of China. A large scale of mountain rock avalanche occurred in Pusa village, Zhangjiawan town, Nayong county, Guizhou Province at about 10:30 on August 28, 2017. The rock mass with the volume of 49.1×104 m3 moved down and scraped the original loose deposits and finally formed deposits of 82.3×104 m3, which destroyed parts of Pusa village, resulted in the death of 26 persons and missing of 9 persons. Based on site investigation, unmanned aerial vehicle(UAV)photography and ground based synthetic aperture radar(GBSAR)monitoring and other technologies, this paper provides a detailed description on the characteristics and a comprehensive analysis on the dynamic process and failure mechanism of the rock avalanche. The preliminary study suggested that the rock masses of the source area were shattered due to the underground mining activities. The shattered rock masses suffered long-term effects of gravity, which eventually resulted the failure of the rock masses. The movement of the rock avalanche lasted for 7 minutes and 21 seconds in which the main rock masses failure lasted for only 26 seconds with the long runout of 788 m and the maximum speed of 43.83 m·s-1, belonging to typical high speed and long runout rock avalanche. There will be a big attribution if such case can be studied further. It can provide the significant experience on dealing with this kind of rock masses failure and how to provide advice on early warning and remediation project on similar cases in southwestern mountain areas of China.
The goal of design for an excavated slope is to determine a slope angle and a slope height within a design value of safety factor. Therefore, the purpose of searching for the potential slip surface is to find out a plane where the minimum ratio of shear resistance and force occurs under the design value of safety factor. This paper presents a very simple exponential curve searching method. It can be used to search for the minimum value of safety factor in a slope with groundwater and determine the corresponding slope angle and height. The curve searching starts from the slope shoulder. The searching continues along the upper slope at an equal interval and generates a family of curves going through the slope toe and the specified point on the upper slope as the power continues to increase from 1. They can be treated as potential shear surfaces, which will allow us to delineate a potential sliding body. The sliding body is then divided into a number of vertical slices so that shear forces and shear resistance and their horizontal and vertical components of forces can be calculated for each slice. According to parallelogram law of forces, one can find the resultant force from the horizontal and vertical components of forces from all the slices and the resultant strength in a similar way. By comparing the shear strength and shear force along this sliding surface, one can obtain the ratio of the shear resistance and shear force. By comparing the ratios between those potential sliding surfaces, a minimum ratio can be found for each family of curves. The searching continues until the minimum ratio is equal to the design factor of safety. For comparison we use the Sarma method to calculate the minimum safety factor of the slope body delineated by the exponential curve searching method. Three case studies are used to demonstrate the applicability of the exponential curve searching method in comparison with other methods. At the end we recommend that the minimum safety factor be used as a major standard guideline for slope design. The goal of design for an excavated slope is to determine a slope angle and a slope height within a design value of safety factor. Therefore, the purpose of searching for the potential slip surface is to find out a plane where the minimum ratio of shear resistance and force occurs under the design value of safety factor. This paper presents a very simple exponential curve searching method. It can be used to search for the minimum value of safety factor in a slope with groundwater and determine the corresponding slope angle and height. The curve searching starts from the slope shoulder. The searching continues along the upper slope at an equal interval and generates a family of curves going through the slope toe and the specified point on the upper slope as the power continues to increase from 1. They can be treated as potential shear surfaces, which will allow us to delineate a potential sliding body. The sliding body is then divided into a number of vertical slices so that shear forces and shear resistance and their horizontal and vertical components of forces can be calculated for each slice. According to parallelogram law of forces, one can find the resultant force from the horizontal and vertical components of forces from all the slices and the resultant strength in a similar way. By comparing the shear strength and shear force along this sliding surface, one can obtain the ratio of the shear resistance and shear force. By comparing the ratios between those potential sliding surfaces, a minimum ratio can be found for each family of curves. The searching continues until the minimum ratio is equal to the design factor of safety. For comparison we use the Sarma method to calculate the minimum safety factor of the slope body delineated by the exponential curve searching method. Three case studies are used to demonstrate the applicability of the exponential curve searching method in comparison with other methods. At the end we recommend that the minimum safety factor be used as a major standard guideline for slope design.
The NSFC proposals and grants of engineering geology in 2017 are analyzed. The number of proposals has increased. The number of Young Scientists Fund and Excellent Young Scientists Fund proposals increased significantly in this year. The peer-review referees well handled the scale of peer-review on the proposals. The age distribution of the General Program applicants tends to be double-peak structure. The age distribution of the Young Scientists Fund applicant tends to be reasonable. The applicants of Key Program are older in age than average but tend to become younger than that in last year. The application of engineering geology has been funded in several different project types, showing a growing competitive trend. The NSFC proposals and grants of engineering geology in 2017 are analyzed. The number of proposals has increased. The number of Young Scientists Fund and Excellent Young Scientists Fund proposals increased significantly in this year. The peer-review referees well handled the scale of peer-review on the proposals. The age distribution of the General Program applicants tends to be double-peak structure. The age distribution of the Young Scientists Fund applicant tends to be reasonable. The applicants of Key Program are older in age than average but tend to become younger than that in last year. The application of engineering geology has been funded in several different project types, showing a growing competitive trend.
The Badong International Geohazards Symposium(BIGS 2017) and the 7th China Youth Symposium on Engineering Geology(CYSEG)were successfully held in Badong county, Hubei province on 25th to 28th of August 2017. The theme of the CYSEG is "Stability analysis and control of landslide", which is jointly organized by China University of Geosciences(Wuhan) and Youth Committee of Engineering Geology. There are almost 200 participants from domestic and overseas universities, research institutes and the industry. The CYSEG is composed of two parts:academic seminar and field geological survey. Among them, academic seminar includes keynote speeches and discussions in association with comments from invited senior experts. In the atmosphere of free and active, participants discussed and interacted in-depth on the hot and difficult issues of landslide stability analysis and control. CYSEG has achieved the goal of sharing new ideas, spreading new thinking and refining new views. In addition, the organizing committee secretariat has established a WeChat service group, which provides real-time online communication platform for participants. The Badong International Geohazards Symposium(BIGS 2017) and the 7th China Youth Symposium on Engineering Geology(CYSEG)were successfully held in Badong county, Hubei province on 25th to 28th of August 2017. The theme of the CYSEG is "Stability analysis and control of landslide", which is jointly organized by China University of Geosciences(Wuhan) and Youth Committee of Engineering Geology. There are almost 200 participants from domestic and overseas universities, research institutes and the industry. The CYSEG is composed of two parts:academic seminar and field geological survey. Among them, academic seminar includes keynote speeches and discussions in association with comments from invited senior experts. In the atmosphere of free and active, participants discussed and interacted in-depth on the hot and difficult issues of landslide stability analysis and control. CYSEG has achieved the goal of sharing new ideas, spreading new thinking and refining new views. In addition, the organizing committee secretariat has established a WeChat service group, which provides real-time online communication platform for participants.
The development history of Journal of Engineering Geology(JEG)in the past decade was reviewed and future development methods was introduced. The citation indices and source indices of JEG were collected and analyzed. The results are as follows. (1)The total cites and non-self total cites rose as liner style, and impact factor had wave-like increasing tendency. (2)International influence of JEG was well. (3)Freelance numbers and published numbers of papers increased year by year; the rejection rate was about 70%. (4)Average author numbers per paper was increased to 4.1 in 2016 from 3.4 in 2006. (5)Authors with most papers published(top 30) and colleges and institutes with most papers published(top 30)give JEG a clear mind to grasp core authors and institutions.(6)Main subjects of published papers were geology, architecture and civil engineering, et al.(7)Average number of citation grown rapidly. The scope and depth of citation were strengthened obviously.(8)Average period of publication from 2006 to 2017 was 282 days, which is a little longer. The next emphases are concluded. (1)Optimize subject distribution and invite high quality papers. (2)Control peer review quality strictly and shorten publication period. (3)Expand the influence of JEG by using new technique as WeChat and XML. The development history of Journal of Engineering Geology(JEG)in the past decade was reviewed and future development methods was introduced. The citation indices and source indices of JEG were collected and analyzed. The results are as follows. (1)The total cites and non-self total cites rose as liner style, and impact factor had wave-like increasing tendency. (2)International influence of JEG was well. (3)Freelance numbers and published numbers of papers increased year by year; the rejection rate was about 70%. (4)Average author numbers per paper was increased to 4.1 in 2016 from 3.4 in 2006. (5)Authors with most papers published(top 30) and colleges and institutes with most papers published(top 30)give JEG a clear mind to grasp core authors and institutions.(6)Main subjects of published papers were geology, architecture and civil engineering, et al.(7)Average number of citation grown rapidly. The scope and depth of citation were strengthened obviously.(8)Average period of publication from 2006 to 2017 was 282 days, which is a little longer. The next emphases are concluded. (1)Optimize subject distribution and invite high quality papers. (2)Control peer review quality strictly and shorten publication period. (3)Expand the influence of JEG by using new technique as WeChat and XML.
On June 24, 2017 a super-large catastrophic rock avalanche-debris flow of 800×104 m3 took place at Xinmo village, Maoxian county of Sichuan Province. Based on the field investigation, remote sensing interpretation and data analysis, the paper studies the geo-environmental conditions of the rock avalanche, the characteristics of failure, movement and deposition, and the triggering actions of rainfall and earthquakes. The main effects on mobility of rock debris and the hazardous mechanism are discussed. The new technology and method of monitoring and warning for such geohazards are evaluated. It is believed as follows. (1)Xinmo village is located in the deposit of an old large landslide before the 1933 Diexi MS 7.5 earthquake. The multiple strong historic-prehistoric earthquakes and the annual rainfall not only made the surface unloaded belt of Triassic slate slope spelled, but also damaged and weakened the rockmass integrity and strength. There have developed large tensional fissures in the ridge slope before year 2003 and existed remarkable emplacement portent before failure. Therefore, the event is essentially a post-earthquake, high speed rock avalanche-debris flow. (2)The rock avalanche is about 150×104 m3 but scratched and entrained a total of 600×104 m3 old colluviums. The huge impact on the old colluviums made the inner soil arching effect suddenly lost. The effect of entrainment of the old colluviums greatly increased their mobility and diffusion but the large entrained colluviums conversely made the whole mass not flowing further. Such a failure mechanism of impact-loading and entrainment is similar to the former landslides in Xintan, Yigong and Nayong. (3)The seismic signals generated by rock avalanche clearly display the process of collapsing, impacting, moving and depositing. The emplacement monitoring of multi-temporal InSAR data clearly displayed the displacement precursor on the slope. The combination of two technologies is a promising new method of early identification, evaluation and warning of similar landslide of ultra-sight and in difficult geo-environment. Finally, with regard to the old and new fissures and their separated blocks, it is suggested to immediately make detailed investigation, risk assessment and monitoring-warning so as to avoid similar disasters. On June 24, 2017 a super-large catastrophic rock avalanche-debris flow of 800×104 m3 took place at Xinmo village, Maoxian county of Sichuan Province. Based on the field investigation, remote sensing interpretation and data analysis, the paper studies the geo-environmental conditions of the rock avalanche, the characteristics of failure, movement and deposition, and the triggering actions of rainfall and earthquakes. The main effects on mobility of rock debris and the hazardous mechanism are discussed. The new technology and method of monitoring and warning for such geohazards are evaluated. It is believed as follows. (1)Xinmo village is located in the deposit of an old large landslide before the 1933 Diexi MS 7.5 earthquake. The multiple strong historic-prehistoric earthquakes and the annual rainfall not only made the surface unloaded belt of Triassic slate slope spelled, but also damaged and weakened the rockmass integrity and strength. There have developed large tensional fissures in the ridge slope before year 2003 and existed remarkable emplacement portent before failure. Therefore, the event is essentially a post-earthquake, high speed rock avalanche-debris flow. (2)The rock avalanche is about 150×104 m3 but scratched and entrained a total of 600×104 m3 old colluviums. The huge impact on the old colluviums made the inner soil arching effect suddenly lost. The effect of entrainment of the old colluviums greatly increased their mobility and diffusion but the large entrained colluviums conversely made the whole mass not flowing further. Such a failure mechanism of impact-loading and entrainment is similar to the former landslides in Xintan, Yigong and Nayong. (3)The seismic signals generated by rock avalanche clearly display the process of collapsing, impacting, moving and depositing. The emplacement monitoring of multi-temporal InSAR data clearly displayed the displacement precursor on the slope. The combination of two technologies is a promising new method of early identification, evaluation and warning of similar landslide of ultra-sight and in difficult geo-environment. Finally, with regard to the old and new fissures and their separated blocks, it is suggested to immediately make detailed investigation, risk assessment and monitoring-warning so as to avoid similar disasters.
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2018, 26(1): 0-0.
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2018, 26(1): 273-274.
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2018, 26(1): 275-277.
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