2020 Vol. 28, No. 2

Others
The problem of the Yellow River is reflected from the river, formed in the region, and rooted in the land. In light of the characteristics and challenges associated with geoscience problems in succeeding the high-quality development of the Yellow River Basin, this paper proposes the concept of so-called"livable Yellow River", which is consist of five core aspects in a systematic and scientific framework, namely the"Safe Yellow River", the"Green Yellow River", the"Ecological Yellow River", the"Harmonious Yellow River" and the"Intelligent Yellow River". The associated scientific connotation and major research contents of each aspect are illustrated in this paper. Specifically, (1)on the basis of the engineering geology, the"Safe Yellow River" aims to solve problems encountered in the geological surface process and the related disastrous impacts, so as to meet the geological safety requirements and build the Yellow River safety system; (2)on the basis of hydrogeology, the"Green Yellow River" focuses on the water cycle process and the related impacts on water and soil environment, thus constructs a green Yellow River system; (3)on the basis of the environmental geology, the "Ecological Yellow River" explores the evolution law of ecosystem and the related ecological barrier effect, and establishes an ecological Yellow River system; (4)on the basis of the resource geology, the "Harmonious Yellow River" studies the development mode of resource exploitation and people-land coordination in the Yellow River Basin, and builds a harmonious Yellow River system; (5)on the basis of the big data and information science, "Intelligent Yellow River" studies the geological information integration and intelligent decision-making platform of the Yellow River Basin, and constructs the intelligent Yellow River system. These five parts support and integrate each other to jointly solve the core and key issues of the livable Yellow River, so as to provide a scientific and technological support in ensuring the long-term stability of the Yellow River and promoting the high-quality development of the entire river basin, and ultimately forming a"Happiness Yellow River" that benefits the Chinese nation. The problem of the Yellow River is reflected from the river, formed in the region, and rooted in the land. In light of the characteristics and challenges associated with geoscience problems in succeeding the high-quality development of the Yellow River Basin, this paper proposes the concept of so-called"livable Yellow River", which is consist of five core aspects in a systematic and scientific framework, namely the"Safe Yellow River", the"Green Yellow River", the"Ecological Yellow River", the"Harmonious Yellow River" and the"Intelligent Yellow River". The associated scientific connotation and major research contents of each aspect are illustrated in this paper. Specifically, (1)on the basis of the engineering geology, the"Safe Yellow River" aims to solve problems encountered in the geological surface process and the related disastrous impacts, so as to meet the geological safety requirements and build the Yellow River safety system; (2)on the basis of hydrogeology, the"Green Yellow River" focuses on the water cycle process and the related impacts on water and soil environment, thus constructs a green Yellow River system; (3)on the basis of the environmental geology, the "Ecological Yellow River" explores the evolution law of ecosystem and the related ecological barrier effect, and establishes an ecological Yellow River system; (4)on the basis of the resource geology, the "Harmonious Yellow River" studies the development mode of resource exploitation and people-land coordination in the Yellow River Basin, and builds a harmonious Yellow River system; (5)on the basis of the big data and information science, "Intelligent Yellow River" studies the geological information integration and intelligent decision-making platform of the Yellow River Basin, and constructs the intelligent Yellow River system. These five parts support and integrate each other to jointly solve the core and key issues of the livable Yellow River, so as to provide a scientific and technological support in ensuring the long-term stability of the Yellow River and promoting the high-quality development of the entire river basin, and ultimately forming a"Happiness Yellow River" that benefits the Chinese nation.
The deformation and failure of rock mass structure is an asymptotic process, which cannot be described by conventional strength design and limit analysis. After reviewing the methods of failure control and deformation control of rock mass structure, we proposed a cracking control method, which should be the final control of the deformation and failure of rock mass structure. We analysed the difficulties of cracking simulation of rock mass structure, and expounded the theoretical basses for describing it by unbalanced force. We analysed the correlations between cracking and unbalanced force by three numerical cases: uniaxial compression test, excavation and unloading of slope and arch dam cracking test. It is proposed that the irreversible valley width reduction caused by impounding is also the result of unbalanced force: the pore water pressure shrinks the yield surface, making that the original stress state of rock mass exceeds the yield surface, resulting in unbalanced force and irreversible plastic deformation. Unbalanced force describes the distance from the unbalanced state to the balanced state of the rock mass structure, and the general trend of the evolution of the unbalanced rock mass structure obeys the principle of minimum plastic complementary energy. Unbalanced force can not only be used as the criterion of deformation and failure of rock mass structure, but also provide corresponding reinforcement measurements, which is of great engineering significance. The deformation and failure of rock mass structure is an asymptotic process, which cannot be described by conventional strength design and limit analysis. After reviewing the methods of failure control and deformation control of rock mass structure, we proposed a cracking control method, which should be the final control of the deformation and failure of rock mass structure. We analysed the difficulties of cracking simulation of rock mass structure, and expounded the theoretical basses for describing it by unbalanced force. We analysed the correlations between cracking and unbalanced force by three numerical cases: uniaxial compression test, excavation and unloading of slope and arch dam cracking test. It is proposed that the irreversible valley width reduction caused by impounding is also the result of unbalanced force: the pore water pressure shrinks the yield surface, making that the original stress state of rock mass exceeds the yield surface, resulting in unbalanced force and irreversible plastic deformation. Unbalanced force describes the distance from the unbalanced state to the balanced state of the rock mass structure, and the general trend of the evolution of the unbalanced rock mass structure obeys the principle of minimum plastic complementary energy. Unbalanced force can not only be used as the criterion of deformation and failure of rock mass structure, but also provide corresponding reinforcement measurements, which is of great engineering significance.
The interlayer staggered zones in the basalt are widely distributed in the Baihetan hydropower project area in Jinsha River Basin, China. They are filled with gravel, debris, and mud. The mud is easy to be destructed. After water impoundment, the seepage gradient in the interlayer staggered zones would increase with the effects of the high water head difference and seepage control measures. Seepage failure can happen in the zones. We establish a 3D finite element fine model of the left bank of the dam area. We use a method of interpolation from different sections to determine water distribution in mountain boundary without observation data. The results show that the existing seepage control measures have effectively control the seepage pressure. The hydraulic gradient in some areas of the interlayer shear weakness zones C2 is greater than the allowable gradient, and seepage failure can happen in these areas. The seepage-prevention hole and the reinforced curtain are effective preventions to decrease gradient, which can block reservoir water better. Moreover, the preventions can block the reservoir water to some extent when the curtain locally fails, which can ensure the seepage stability around the underground powerhouse. The interlayer staggered zones in the basalt are widely distributed in the Baihetan hydropower project area in Jinsha River Basin, China. They are filled with gravel, debris, and mud. The mud is easy to be destructed. After water impoundment, the seepage gradient in the interlayer staggered zones would increase with the effects of the high water head difference and seepage control measures. Seepage failure can happen in the zones. We establish a 3D finite element fine model of the left bank of the dam area. We use a method of interpolation from different sections to determine water distribution in mountain boundary without observation data. The results show that the existing seepage control measures have effectively control the seepage pressure. The hydraulic gradient in some areas of the interlayer shear weakness zones C2 is greater than the allowable gradient, and seepage failure can happen in these areas. The seepage-prevention hole and the reinforced curtain are effective preventions to decrease gradient, which can block reservoir water better. Moreover, the preventions can block the reservoir water to some extent when the curtain locally fails, which can ensure the seepage stability around the underground powerhouse.
This paper applies non-contact acquisition techniques and 3D fracture network modelling to study the discontinuities of high-steep slope located in Miansi Town, Wenchuan County. UAV, 3D laser scanning, and Close Range Photogrammetry are used to generate 3D DEM model and to recognize and interpret discontinuities. Especially, UAV and Close Range Photogrammetry are applied to recognize and interpret controlling large discontinuities and 6663 stochastic structural fractures. Based on the collected data, this paper propose a 3D fracture network modelling method that fits for large sampling windows of high-steep slopes. Stochastic mathematics and spatial geometric derivation methods are used to determine the diameter, orientation, and density of 3D fractures. This method is much easier and to the point, as well as has a higher accuracy according to field verification. This paper applies non-contact acquisition techniques and 3D fracture network modelling to study the discontinuities of high-steep slope located in Miansi Town, Wenchuan County. UAV, 3D laser scanning, and Close Range Photogrammetry are used to generate 3D DEM model and to recognize and interpret discontinuities. Especially, UAV and Close Range Photogrammetry are applied to recognize and interpret controlling large discontinuities and 6663 stochastic structural fractures. Based on the collected data, this paper propose a 3D fracture network modelling method that fits for large sampling windows of high-steep slopes. Stochastic mathematics and spatial geometric derivation methods are used to determine the diameter, orientation, and density of 3D fractures. This method is much easier and to the point, as well as has a higher accuracy according to field verification.
Slaking process of claystone is vulnerable to environmental condition. The acid rain can significantly affect the process. The corresponding mechanism remains to be studied. Traditionally, the slaking characteristic of claystone is evaluated by second cycle slake durability index which is determined by the mass of the residual particles larger than 2 mm only. Such evaluation fails to reflect the characteristics of the overall particle size distribution. This paper takes the Panzhihua landslide as an example. The site is located in the typical acid rain area. The silty mudstone samples located on the sliding surface are processed. Then a series of slaking experiments are carried out by the use of solutions with different pH values. Based on the fractal theory, the fractal dimension is introduced to quantitatively describe the slaking characteristics of silty mudstone. The correlations between fractal dimension with acid rain duration and acidity of rainfall are established, respectively. The substantial cause for the slaking characteristic differences due to different rainfall acidity is determined through analyzing the solution chemical composition. The results highlight that the fractal theory can better reflect the acid rain slaking characteristics of silty mudstone. The higher the fractal dimension is, the higher the slaking degree. The logarithmic positive correlation exists between the fractal dimension and the duration of acid rain, the final fractal dimension and the acidity of rainfall. The reason for the slaking characteristics difference under various rainfall acidities lies in the different degrees of dolomite and calcite dissolutions. Conclusions of this paper can be taken as references for engineering property evaluation of rock mass in acid rain area. Slaking process of claystone is vulnerable to environmental condition. The acid rain can significantly affect the process. The corresponding mechanism remains to be studied. Traditionally, the slaking characteristic of claystone is evaluated by second cycle slake durability index which is determined by the mass of the residual particles larger than 2 mm only. Such evaluation fails to reflect the characteristics of the overall particle size distribution. This paper takes the Panzhihua landslide as an example. The site is located in the typical acid rain area. The silty mudstone samples located on the sliding surface are processed. Then a series of slaking experiments are carried out by the use of solutions with different pH values. Based on the fractal theory, the fractal dimension is introduced to quantitatively describe the slaking characteristics of silty mudstone. The correlations between fractal dimension with acid rain duration and acidity of rainfall are established, respectively. The substantial cause for the slaking characteristic differences due to different rainfall acidity is determined through analyzing the solution chemical composition. The results highlight that the fractal theory can better reflect the acid rain slaking characteristics of silty mudstone. The higher the fractal dimension is, the higher the slaking degree. The logarithmic positive correlation exists between the fractal dimension and the duration of acid rain, the final fractal dimension and the acidity of rainfall. The reason for the slaking characteristics difference under various rainfall acidities lies in the different degrees of dolomite and calcite dissolutions. Conclusions of this paper can be taken as references for engineering property evaluation of rock mass in acid rain area.
In this paper,the TAW-2000 servo triaxial testing machine and acoustic emission testing equipment are used to analyze the characteristics of granite under uniaxial compression at 25~650℃ after high temperature. The variation rules of longitudinal wave velocity,maximum strength and AE counts with time are analyzed respectively. The results show that the P-wave velocity and the maximum strength of granite decrease with the increase of temperature. When the temperature exceeds 500℃,the P-wave velocity and the maximum strength begin to decrease greatly. It can be observed that the threshold temperature of granite is about 500℃. The acoustic emission signal is always accompanied by the loading process of granite after high temperature action,and has a good corresponding relationship with the stress versus time curve. The acoustic emission activity of granite after different temperature actions is different. The higher the temperature is,the stronger the acoustic emission activity is. Before 500℃,the granite samples show splitting failure,and the temperature reaches 500℃,the granite samples show shear failure. The high temperature causes the internal structure of granite samples to change and the cracks in the samples gradually expand,penetrate,and finally destroy. In this paper,the TAW-2000 servo triaxial testing machine and acoustic emission testing equipment are used to analyze the characteristics of granite under uniaxial compression at 25~650℃ after high temperature. The variation rules of longitudinal wave velocity,maximum strength and AE counts with time are analyzed respectively. The results show that the P-wave velocity and the maximum strength of granite decrease with the increase of temperature. When the temperature exceeds 500℃,the P-wave velocity and the maximum strength begin to decrease greatly. It can be observed that the threshold temperature of granite is about 500℃. The acoustic emission signal is always accompanied by the loading process of granite after high temperature action,and has a good corresponding relationship with the stress versus time curve. The acoustic emission activity of granite after different temperature actions is different. The higher the temperature is,the stronger the acoustic emission activity is. Before 500℃,the granite samples show splitting failure,and the temperature reaches 500℃,the granite samples show shear failure. The high temperature causes the internal structure of granite samples to change and the cracks in the samples gradually expand,penetrate,and finally destroy.
The jointed rock masses with incomplete end joints and coalescence mechanisms of rock slopes are often encountered in engineering construction. They are complex. In order to reveal the relationship between the failure characteristics and dilatancy effect of end rock bridge under different joint connectivity rates and normal stresses, we carry out the direct shear test of the rock bridge to explore the failure process of the front locked section slope. The whole process of shear stress change is analyzed by high-speed photography and AE characteristic parameters. After test, we find that the shear failure process of the end direct shear specimens can be divided into five stages: crack compaction, stable crack propagation, progressive propagation, strain softening and residual strength stage. The decrease of joint connectivity rate and the increase of normal stress lead to the increase of peak shear displacement and peak shear stress. The joint connectivity rate and normal stress have significant influence on the failure characteristics of rock mass. When the joint connectivity rate is high and the normal stress is small, the cracks propagate in a straight line. With the decrease of the length of joint connectivity rate, the phenomenon of shear dilatancy occurs, and the cracks become irregular curves. Meanwhile, the increase of normal stress causes the dilatancy phenomenon to fluctuate. The AE characteristics are consistent with the rock bridge crossing process. The peak number of AE events increases with the decrease of the joint connectivity rate and the increase of normal stress. The tests demonstrate that the microscopic failure characteristics and dilatancy effect of rock bridge are extremely significant for studying the failure mechanism of the locked section slope as a guide. The jointed rock masses with incomplete end joints and coalescence mechanisms of rock slopes are often encountered in engineering construction. They are complex. In order to reveal the relationship between the failure characteristics and dilatancy effect of end rock bridge under different joint connectivity rates and normal stresses, we carry out the direct shear test of the rock bridge to explore the failure process of the front locked section slope. The whole process of shear stress change is analyzed by high-speed photography and AE characteristic parameters. After test, we find that the shear failure process of the end direct shear specimens can be divided into five stages: crack compaction, stable crack propagation, progressive propagation, strain softening and residual strength stage. The decrease of joint connectivity rate and the increase of normal stress lead to the increase of peak shear displacement and peak shear stress. The joint connectivity rate and normal stress have significant influence on the failure characteristics of rock mass. When the joint connectivity rate is high and the normal stress is small, the cracks propagate in a straight line. With the decrease of the length of joint connectivity rate, the phenomenon of shear dilatancy occurs, and the cracks become irregular curves. Meanwhile, the increase of normal stress causes the dilatancy phenomenon to fluctuate. The AE characteristics are consistent with the rock bridge crossing process. The peak number of AE events increases with the decrease of the joint connectivity rate and the increase of normal stress. The tests demonstrate that the microscopic failure characteristics and dilatancy effect of rock bridge are extremely significant for studying the failure mechanism of the locked section slope as a guide.
Soil-rock mixture (S-RM) is one of the widely distributed and unique geological materials in China and around the world. It is composed of loose rocks and soil, and has become a key carrier for mountain geological hazards. The complex structure of S-RM is the key to evaluate its special physical and mechanical properties. In this paper, the strength, deformation and permeability characteristics of S-RM and its structural control mechanisms are thoroughly studied, based on the multi-scale macro and micro tests, physical and mechanical field tests, numerical simulation, in order to interpret the control mechanisms of crucial structure factors. The factors include rock proportion, soil-rock shape, matrix composition and internal soil-rock granularity composition. Furthermore, the soil-rock control laws of the randomness of the S-RM strength and deformation characteristics are determined. In addition, much more accurate acquisition methods of strength parameters in different structural states are also proposed. The nonlinear seepage calculation model and its optimal design method of anti-seepage deformation are obtained, through the study on the nonlinear permeability characteristics of S-RM with different stone contents. In summary, this study provides a certain theoretical support for the comprehensive establishment of new generation of S-MR landslide early-warning system, based on the real soil-rock structures and nonlinear constitutive relation. Soil-rock mixture (S-RM) is one of the widely distributed and unique geological materials in China and around the world. It is composed of loose rocks and soil, and has become a key carrier for mountain geological hazards. The complex structure of S-RM is the key to evaluate its special physical and mechanical properties. In this paper, the strength, deformation and permeability characteristics of S-RM and its structural control mechanisms are thoroughly studied, based on the multi-scale macro and micro tests, physical and mechanical field tests, numerical simulation, in order to interpret the control mechanisms of crucial structure factors. The factors include rock proportion, soil-rock shape, matrix composition and internal soil-rock granularity composition. Furthermore, the soil-rock control laws of the randomness of the S-RM strength and deformation characteristics are determined. In addition, much more accurate acquisition methods of strength parameters in different structural states are also proposed. The nonlinear seepage calculation model and its optimal design method of anti-seepage deformation are obtained, through the study on the nonlinear permeability characteristics of S-RM with different stone contents. In summary, this study provides a certain theoretical support for the comprehensive establishment of new generation of S-MR landslide early-warning system, based on the real soil-rock structures and nonlinear constitutive relation.
Natural gas hydrate(NGH) is the most promising clean alternative energy resource for world, which will be the strategic breakthrough of energy revolution in the future. Because the decomposition of NGH is a complicated physical and chemical process accompanied by phase change, there are still many bottleneck problems to be resolved with respect to the safe and economic exploitation of NGH. At present, the depressurization method is relatively economic and effective, but the average daily production of natural gas is far from the demand of commercial development. Based on the analysis of the bottleneck problems in depressurization method, a novel method for natural gas hydrate production, depressurization and backfilling with in-situ supplemental heat, is proposed. Three basic principles of the method are emphatically analyzed. The technology scheme, key techniques and implementation steps of the method are introduced. The conclusions are as follows: (1)The achievement of large-scale production of NGH by depressurization depend on three key factors, namely heat supply, reservoir stability and reservoir permeability. (2)Based on the three principles of depressurization, in-situ supplemental heat and backfilling and increased permeability, the novel method was proposed. In this method, calcium oxide(CaO)powder is injected into the hydrate reservoir, which will provide a large amount of heat for the decomposition of NGH. At the same time, the Ca(OH)2 produced by the reaction will backfill the void volume left by hydrate decomposition and improve the permeability of the reservoir. (3)This study put forward the technology scheme, key techniques and implementation steps of the novel method. The method is mainly implemented in three stages, i.e., horizontal well drilling and completion, high-pressure air powder injection and depressurization and backfilling. In the future, it is necessary to strengthen international scientific research cooperation, deepen interdisciplinary R&D of innovative technologies, and realize the large-scale production of NGH as soon as possible. Natural gas hydrate(NGH) is the most promising clean alternative energy resource for world, which will be the strategic breakthrough of energy revolution in the future. Because the decomposition of NGH is a complicated physical and chemical process accompanied by phase change, there are still many bottleneck problems to be resolved with respect to the safe and economic exploitation of NGH. At present, the depressurization method is relatively economic and effective, but the average daily production of natural gas is far from the demand of commercial development. Based on the analysis of the bottleneck problems in depressurization method, a novel method for natural gas hydrate production, depressurization and backfilling with in-situ supplemental heat, is proposed. Three basic principles of the method are emphatically analyzed. The technology scheme, key techniques and implementation steps of the method are introduced. The conclusions are as follows: (1)The achievement of large-scale production of NGH by depressurization depend on three key factors, namely heat supply, reservoir stability and reservoir permeability. (2)Based on the three principles of depressurization, in-situ supplemental heat and backfilling and increased permeability, the novel method was proposed. In this method, calcium oxide(CaO)powder is injected into the hydrate reservoir, which will provide a large amount of heat for the decomposition of NGH. At the same time, the Ca(OH)2 produced by the reaction will backfill the void volume left by hydrate decomposition and improve the permeability of the reservoir. (3)This study put forward the technology scheme, key techniques and implementation steps of the novel method. The method is mainly implemented in three stages, i.e., horizontal well drilling and completion, high-pressure air powder injection and depressurization and backfilling. In the future, it is necessary to strengthen international scientific research cooperation, deepen interdisciplinary R&D of innovative technologies, and realize the large-scale production of NGH as soon as possible.
Bentonite pellet mixtures are considered as an alternative buffer/backfilling materials for high-level radioactive waste(HLW)repository. The packing and hydro-mechanical behaviour of bentonite pellet mixtures are of great significance for the safety evaluation of the HLW repository. In this paper, previous researches on the packing and hydro-mechanical behaviour of bentonite pellet mixtures are systematically reviewed and summarized. They include the packing dry density and homogeneity, water retention, structural change, hydraulic behaviour, swelling and compression behaviour as well as constitutive model. Meanwhile, several research subjects worthing further investigation are pointed out. Results in the literature indicate that the packing behaviour are highly dependent on the gradation. Upon wetting, the initial loose-structured pellet mixture can gradually transfer to cemented state and finally present a homogeneous appearance at saturation, accompanied with pellet breakage and movement, which can in turn affect the hydro-mechnical behaviour. Considering the complexity of the operation conditions in a HLW repository, further investigations on the emplacement technique and the hydro-mechanical behaviour under coupled thermo-hydro-chemo-mechanical conditions should be carried out. Bentonite pellet mixtures are considered as an alternative buffer/backfilling materials for high-level radioactive waste(HLW)repository. The packing and hydro-mechanical behaviour of bentonite pellet mixtures are of great significance for the safety evaluation of the HLW repository. In this paper, previous researches on the packing and hydro-mechanical behaviour of bentonite pellet mixtures are systematically reviewed and summarized. They include the packing dry density and homogeneity, water retention, structural change, hydraulic behaviour, swelling and compression behaviour as well as constitutive model. Meanwhile, several research subjects worthing further investigation are pointed out. Results in the literature indicate that the packing behaviour are highly dependent on the gradation. Upon wetting, the initial loose-structured pellet mixture can gradually transfer to cemented state and finally present a homogeneous appearance at saturation, accompanied with pellet breakage and movement, which can in turn affect the hydro-mechnical behaviour. Considering the complexity of the operation conditions in a HLW repository, further investigations on the emplacement technique and the hydro-mechanical behaviour under coupled thermo-hydro-chemo-mechanical conditions should be carried out.
Microbially Induced Carbonate Precipitation (MICP) is a new kind of green and low-carbon soil modification technique. At present, this technique is mainly applicable to sandy soil with good permeability. A two-phase treatment method is commonly used, where the bacterial solution and the cementation solution are applied separately. However, for clayey soils with relatively poor permeability, the traditional two-phase treatment method is difficult to apply. Therefore, a new one-phase cementation method is introduced in this paper. It is a mixed application of bacterial solution and cementation solution. It provides a lag period for bacterial hydrolysis by adjusting the initial pH value of the solution, avoids microbial flocculation blocking the pore, makes the mixed solution evenly distributed in a certain depth range of soil, and thus significantly improves the cementation quality. The mixed liquid is sprayed to the surface of soil to have it treated by MICP. After the treatment, the initial structural strength of soil surface at different depths is tested by SMP-1. The spatial difference of soil mechanical properties is analyzed. The cementation quality of soil is quantitatively evaluated. In addition, the effects of cementation solution concentration (0.2 M, 0.5 M and 1.0 M) and cementation method (adjusting pH or not) on soil structural strength and MICP modification quality are investigated. The results show that the one-phase MICP technique can significantly improve the structural strength of clay and has good applicability. Within the range of cementation solution concentration not higher than 1.0M, the cementing effect of clay increases with the increase of cementation solution concentration. Comparatively the one-phase cementation method of adjusting pH can improve the depth and homogeneity of soil cementation proactively. One-phase MICP technique is simple and easy to implement, can save costs, and has potential application value on strengthening the surface of clayey soil. Microbially Induced Carbonate Precipitation (MICP) is a new kind of green and low-carbon soil modification technique. At present, this technique is mainly applicable to sandy soil with good permeability. A two-phase treatment method is commonly used, where the bacterial solution and the cementation solution are applied separately. However, for clayey soils with relatively poor permeability, the traditional two-phase treatment method is difficult to apply. Therefore, a new one-phase cementation method is introduced in this paper. It is a mixed application of bacterial solution and cementation solution. It provides a lag period for bacterial hydrolysis by adjusting the initial pH value of the solution, avoids microbial flocculation blocking the pore, makes the mixed solution evenly distributed in a certain depth range of soil, and thus significantly improves the cementation quality. The mixed liquid is sprayed to the surface of soil to have it treated by MICP. After the treatment, the initial structural strength of soil surface at different depths is tested by SMP-1. The spatial difference of soil mechanical properties is analyzed. The cementation quality of soil is quantitatively evaluated. In addition, the effects of cementation solution concentration (0.2 M, 0.5 M and 1.0 M) and cementation method (adjusting pH or not) on soil structural strength and MICP modification quality are investigated. The results show that the one-phase MICP technique can significantly improve the structural strength of clay and has good applicability. Within the range of cementation solution concentration not higher than 1.0M, the cementing effect of clay increases with the increase of cementation solution concentration. Comparatively the one-phase cementation method of adjusting pH can improve the depth and homogeneity of soil cementation proactively. One-phase MICP technique is simple and easy to implement, can save costs, and has potential application value on strengthening the surface of clayey soil.
In the process of urbanization and industrialization in China, the dependence and demand for underground pipelines are increasing, but a series of catastrophic accidents of underground pipeline have occurred in recent years. Therefore, it is urgent to emphasize the study on pipe-soil interaction and failure mechanism. In this paper, based on the quasi-distributed fiber Bragg grating(FBG)technology, a series of plane-strain model tests are conducted in laboratory. The fiber optic strain sensors are employed to investigate stress and deformation characteristics of buried pipes under the action of surface loading. A calculation method of earth pressures around the pipe is proposed based on fiber optic strain measurements. Meanwhile, the particle image velocimetry(PIV)technique is used to obtain the soil deformation around the pipe. Such deformation results are compared to the fiber optic monitoring results. The test results show that the FBG technology can effectively capture the distribution of earth pressure acting on the buried pipe and the evolution of soil strains. The deformation and failure patterns of soil are quite different for pipes with various burial depths. With the increase of burial depth, the soil arching effect becomes more significant. The conclusions drawn in this paper provide useful reference for evaluating underground pipeline hazards and improving monitoring and early warning levels. In the process of urbanization and industrialization in China, the dependence and demand for underground pipelines are increasing, but a series of catastrophic accidents of underground pipeline have occurred in recent years. Therefore, it is urgent to emphasize the study on pipe-soil interaction and failure mechanism. In this paper, based on the quasi-distributed fiber Bragg grating(FBG)technology, a series of plane-strain model tests are conducted in laboratory. The fiber optic strain sensors are employed to investigate stress and deformation characteristics of buried pipes under the action of surface loading. A calculation method of earth pressures around the pipe is proposed based on fiber optic strain measurements. Meanwhile, the particle image velocimetry(PIV)technique is used to obtain the soil deformation around the pipe. Such deformation results are compared to the fiber optic monitoring results. The test results show that the FBG technology can effectively capture the distribution of earth pressure acting on the buried pipe and the evolution of soil strains. The deformation and failure patterns of soil are quite different for pipes with various burial depths. With the increase of burial depth, the soil arching effect becomes more significant. The conclusions drawn in this paper provide useful reference for evaluating underground pipeline hazards and improving monitoring and early warning levels.
Soil-rock mixture slope is a common type of slope in nature, which has obvious heterogeneity and discontinuity. Rheological property of soil is one of the main causes leading to the soil-rock mixture slope deformation and instability. But almost all the existing analyses on the stability of soil-rock mixture slopes neglect the rheological properties of soil. Using digital image processing technology, a soil-rock mixture slope model in the reservoir area of one hydropower station in China is built. Then the strength reduction method in FLAC3D code is adopted to analyze the slope stability. The analysis mainly focuses on the creep characteristics of soil and the effect of the creep parameters on the deformation and stability of the soil-rock mixture slope. The results show that the rheological property of soil can obviously reduce the factor of safety of the soil-rock mixture slope, increase the deformation of the slope, and adversely affect the stability of the slope. The creep viscosity coefficient has a great influence on the long-term stability of slope, and the greater the viscosity coefficient is, the lower the safety factor is. Soil-rock mixture slope is a common type of slope in nature, which has obvious heterogeneity and discontinuity. Rheological property of soil is one of the main causes leading to the soil-rock mixture slope deformation and instability. But almost all the existing analyses on the stability of soil-rock mixture slopes neglect the rheological properties of soil. Using digital image processing technology, a soil-rock mixture slope model in the reservoir area of one hydropower station in China is built. Then the strength reduction method in FLAC3D code is adopted to analyze the slope stability. The analysis mainly focuses on the creep characteristics of soil and the effect of the creep parameters on the deformation and stability of the soil-rock mixture slope. The results show that the rheological property of soil can obviously reduce the factor of safety of the soil-rock mixture slope, increase the deformation of the slope, and adversely affect the stability of the slope. The creep viscosity coefficient has a great influence on the long-term stability of slope, and the greater the viscosity coefficient is, the lower the safety factor is.
Many important soft soil projects need to be repaired quickly after failure, such as foundation pits and subgrade engineering. The appearance of magnesium phosphate cement satisfies the requirements of modern construction. However, the difference of the organic content of soft soil in different regions has an important influence on the properties of the solidified soil. We prepare soil samples with different organic contents by adding humic acid to the soft soil and study the reinforcement of soft soil with different organic contents by magnesium phosphate cement, contrast with the reinforced soft soil of PO cement under the same conditions. Finally, the following laws are obtained through the relevant mechanical tests: in the process of strengthening different organic contents of soft soil, the reinforcement effect can gradually decrease with the increase of organic content. Magnesium phosphate cement is obviously superior in rapid repair and condensation than PO cement. But long-term reinforcement effect of the magnesium phosphate cement in soft soil is not as good as that of PO cement. At the same time, SEM test is used to explain the obtained rules and analyze the microstructure evolution characteristics. Magnesium phosphate cement can be applied to the construction of soft soil repair projects. The research results uniquely analyze the influence of organic content change on the strengthening effect of magnesium phosphate cement, which has guiding and reference significance for reinforcing soft soil projects. Many important soft soil projects need to be repaired quickly after failure, such as foundation pits and subgrade engineering. The appearance of magnesium phosphate cement satisfies the requirements of modern construction. However, the difference of the organic content of soft soil in different regions has an important influence on the properties of the solidified soil. We prepare soil samples with different organic contents by adding humic acid to the soft soil and study the reinforcement of soft soil with different organic contents by magnesium phosphate cement, contrast with the reinforced soft soil of PO cement under the same conditions. Finally, the following laws are obtained through the relevant mechanical tests: in the process of strengthening different organic contents of soft soil, the reinforcement effect can gradually decrease with the increase of organic content. Magnesium phosphate cement is obviously superior in rapid repair and condensation than PO cement. But long-term reinforcement effect of the magnesium phosphate cement in soft soil is not as good as that of PO cement. At the same time, SEM test is used to explain the obtained rules and analyze the microstructure evolution characteristics. Magnesium phosphate cement can be applied to the construction of soft soil repair projects. The research results uniquely analyze the influence of organic content change on the strengthening effect of magnesium phosphate cement, which has guiding and reference significance for reinforcing soft soil projects.
In order to investigate the simplified method for evaluating the shear strength of unsaturated loess, we conduct a series of conventional consolidated quick shear test and the suction test before consolidation as well as after shearing using filter paper method. The data is validated by unsaturated direct shear test. Then we discuss the variation of initial suction and shear suction under normal stress. The research shows that air entry value and residual value of the soil-water characteristic curve control the change of dry density and water content within consolidating. Based on the Vanapalli's model, a simple method to predict the shear strength of loess is gained. The proposed model using the initial soil-water characteristic curve, effective cohesion and effective internal friction angle of soil simplifies the procedure and time of shear strength measurement for unsaturated soil. The model provides a novel technique for the application of unsaturated shear strength theory in engineering practice. In order to investigate the simplified method for evaluating the shear strength of unsaturated loess, we conduct a series of conventional consolidated quick shear test and the suction test before consolidation as well as after shearing using filter paper method. The data is validated by unsaturated direct shear test. Then we discuss the variation of initial suction and shear suction under normal stress. The research shows that air entry value and residual value of the soil-water characteristic curve control the change of dry density and water content within consolidating. Based on the Vanapalli's model, a simple method to predict the shear strength of loess is gained. The proposed model using the initial soil-water characteristic curve, effective cohesion and effective internal friction angle of soil simplifies the procedure and time of shear strength measurement for unsaturated soil. The model provides a novel technique for the application of unsaturated shear strength theory in engineering practice.
This paper analyzes the compression characteristics of calcareous sands from the South China Sea and the Arabian Gulf through a series of oedometer tests. Based on the test results, we obtain the compression index and the plastic work of sand samples with different initial relative density values. At the same time, we evaluate the sand breakage with relative breakage index proposed by Hardin. The relationship between plastic work and relative breakage index as well as compression index is studied to discuss the influence of particle breakage on compression characteristics of calcareous sands. The results show that the mean diameter and the content of calcium carbonate have a significant effect on particle breakage, which is the main factor inducing the compression deformation of calcareous sands. The relative breakage index of calcareous sands mainly associates with the plastic work and the initial relative density. The relationship between relative breakage index and plastic work is a power function by normalizing of relative density. The power function is also satisfactory for the relationship between compression index and relative breakage index. It could be used to evaluate the effect of particle breakage on the compression characteristics of calcareous sands. This paper analyzes the compression characteristics of calcareous sands from the South China Sea and the Arabian Gulf through a series of oedometer tests. Based on the test results, we obtain the compression index and the plastic work of sand samples with different initial relative density values. At the same time, we evaluate the sand breakage with relative breakage index proposed by Hardin. The relationship between plastic work and relative breakage index as well as compression index is studied to discuss the influence of particle breakage on compression characteristics of calcareous sands. The results show that the mean diameter and the content of calcium carbonate have a significant effect on particle breakage, which is the main factor inducing the compression deformation of calcareous sands. The relative breakage index of calcareous sands mainly associates with the plastic work and the initial relative density. The relationship between relative breakage index and plastic work is a power function by normalizing of relative density. The power function is also satisfactory for the relationship between compression index and relative breakage index. It could be used to evaluate the effect of particle breakage on the compression characteristics of calcareous sands.
Monitoring and early warning have become the important means of preventing geohazards with rapid development in technology. A great deal of financial, manpower and physical resources have been adopted to work on landslide monitoring and early warning. However, some technical and managerial personnel have misunderstandings in landslide monitoring and early warning, which seriously affects the geohazards prevention and mitigation effects. Based on research results and lessons learned in practice over recent years, this paper discusses on some basic issues in terms of landslide monitoring and early warning. Main points include:(1)It is not that more monitoring locations and methods are better. The landslide monitoring plan should highlight pertinence, practicability and purpose, and its design and content mainly provide the basis for landslide early warning; (2)The occurrence for many landslides is sudden, and monitoring equipment with self-adaptive data acquisition function should be used to get entire deformation data, especially the accelerated creep stage, to guarantee scientific alert. (3)Monitoring is just a means to an end, while early warning is the end goal. Much attention should be paid on landslide early warning, like regional-scale meteorological early warning and slope-scale landslide early warning; (4)The commonly used early warning models with thresholds have a high rate of false and missing alarms. The study on statistical analysis of historical data, early warning models based on key parameters of deformation, underground water level and precipitation, become a high priority to improve the accuracy and practicality of landslide early warning. Monitoring and early warning have become the important means of preventing geohazards with rapid development in technology. A great deal of financial, manpower and physical resources have been adopted to work on landslide monitoring and early warning. However, some technical and managerial personnel have misunderstandings in landslide monitoring and early warning, which seriously affects the geohazards prevention and mitigation effects. Based on research results and lessons learned in practice over recent years, this paper discusses on some basic issues in terms of landslide monitoring and early warning. Main points include:(1)It is not that more monitoring locations and methods are better. The landslide monitoring plan should highlight pertinence, practicability and purpose, and its design and content mainly provide the basis for landslide early warning; (2)The occurrence for many landslides is sudden, and monitoring equipment with self-adaptive data acquisition function should be used to get entire deformation data, especially the accelerated creep stage, to guarantee scientific alert. (3)Monitoring is just a means to an end, while early warning is the end goal. Much attention should be paid on landslide early warning, like regional-scale meteorological early warning and slope-scale landslide early warning; (4)The commonly used early warning models with thresholds have a high rate of false and missing alarms. The study on statistical analysis of historical data, early warning models based on key parameters of deformation, underground water level and precipitation, become a high priority to improve the accuracy and practicality of landslide early warning.
This paper summarizes the achievements in reduction of geological disasters in China. The areas of the achievements include survey and assessments, monitoring and early warnings, engineering countermeasures, emergency responses, information systems, technical equipment, technical standards, academic research, industry developments and construction of laws. Statistic analysis is used in the paper. Basic data are from national bulletins on geological disasters of P. R. China from 1995 to 2018. They consist of deaths or missing number of people and direct economic losses in a year. The analysis shows that numbers of fatalities by geological disasters are 1205 per year during 1995-2000, 884 per year during 2001-2005, 776 per year during 2006-2010(without the 1765 deaths from the flood-debris of Aug.8, 2010 in Zhouqu city, Gansu province), 395 per year during 2011-2017, and only 112 in 2018. During 2001-2010, the 194702 geological disasters caused direct economic loss of 38.53 billion RMB yuan. Averagely, 19.47 thousand geological disasters per year and 197.9 thousand RMB yuan loss per time. During 2011-2018, the 84718 geological disasters caused direct economic loss of 35.57 billion RMB yuan. Averagely, 10.6 thousand geological disasters per year and 419.9 thousand RMB yuan loss per time. Obviously, the total amount of geological disasters decrease along time, but economic loss increases per time. The proportion of direct economic loss of GDP declined 0.016‰per year since 2001. The prediction accuracy of geological disaster raised from 5%to 20%during 2003-2018. The number of people in urban and rural communities who need emergency hedging decreases. The results show that measurements to reduce geological disasters are prove to be effective. They include geological hazard survey and assessment, monitoring and early warning, geotechnical engineering, relocation and avoidance, emergency response and mitigation management. The paper discusses the current situation and existing problems with geological risk. They include weak disaster reduction culture, immature legal system and limitations of economic loss statistics(not including engineering and construction industry). Finally, the paper proposes a five-in-one partnership for disaster reduction which involves the government, enterprises, individuals, society(including insurance) and academia. This paper summarizes the achievements in reduction of geological disasters in China. The areas of the achievements include survey and assessments, monitoring and early warnings, engineering countermeasures, emergency responses, information systems, technical equipment, technical standards, academic research, industry developments and construction of laws. Statistic analysis is used in the paper. Basic data are from national bulletins on geological disasters of P. R. China from 1995 to 2018. They consist of deaths or missing number of people and direct economic losses in a year. The analysis shows that numbers of fatalities by geological disasters are 1205 per year during 1995-2000, 884 per year during 2001-2005, 776 per year during 2006-2010(without the 1765 deaths from the flood-debris of Aug.8, 2010 in Zhouqu city, Gansu province), 395 per year during 2011-2017, and only 112 in 2018. During 2001-2010, the 194702 geological disasters caused direct economic loss of 38.53 billion RMB yuan. Averagely, 19.47 thousand geological disasters per year and 197.9 thousand RMB yuan loss per time. During 2011-2018, the 84718 geological disasters caused direct economic loss of 35.57 billion RMB yuan. Averagely, 10.6 thousand geological disasters per year and 419.9 thousand RMB yuan loss per time. Obviously, the total amount of geological disasters decrease along time, but economic loss increases per time. The proportion of direct economic loss of GDP declined 0.016‰per year since 2001. The prediction accuracy of geological disaster raised from 5%to 20%during 2003-2018. The number of people in urban and rural communities who need emergency hedging decreases. The results show that measurements to reduce geological disasters are prove to be effective. They include geological hazard survey and assessment, monitoring and early warning, geotechnical engineering, relocation and avoidance, emergency response and mitigation management. The paper discusses the current situation and existing problems with geological risk. They include weak disaster reduction culture, immature legal system and limitations of economic loss statistics(not including engineering and construction industry). Finally, the paper proposes a five-in-one partnership for disaster reduction which involves the government, enterprises, individuals, society(including insurance) and academia.
In recent years, unexpected high-level landslides have been increasing, resulting in adverse effects. This kind of geological hazard investigation is very difficult and concealed. It is difficult to solve the problem of disaster prevention and control by group survey and geological investigation alone. With the continuous improvement of the quality of radar remote sensing satellite data, the SBAS-InSAR technology in synthetic aperture Interferometric Radar(InSAR)provides a new technical approach for deformation detection of large-scale old landslides before disaster. The surface deformation of Wodacun landslide in Jinsha River Basin is monitored by SBAS-InSAR technology. The deformation results from March 30, 2017 to September 28, 2019 are obtained. Strong deformation area(Ⅰradar) and uniform deformation area(Ⅱradar) are delineated. The surface deformation rate, cumulative displacement trend and main crack deformation of the whole and local landslide in the revived area are analyzed. At the same time, the engineering geological survey and review are carried out on the spot. It is found that the resurrection and deformation signs of the old landslide are in good agreement with the interpretation results of the SBAS-InSAR technology. It is clear that the SBAS-InSAR technology has broad application prospects in the field of early warning and monitoring of geological disasters in complex mountain areas, and provides new ideas and references for monitoring and early warning similar to old landslides. In recent years, unexpected high-level landslides have been increasing, resulting in adverse effects. This kind of geological hazard investigation is very difficult and concealed. It is difficult to solve the problem of disaster prevention and control by group survey and geological investigation alone. With the continuous improvement of the quality of radar remote sensing satellite data, the SBAS-InSAR technology in synthetic aperture Interferometric Radar(InSAR)provides a new technical approach for deformation detection of large-scale old landslides before disaster. The surface deformation of Wodacun landslide in Jinsha River Basin is monitored by SBAS-InSAR technology. The deformation results from March 30, 2017 to September 28, 2019 are obtained. Strong deformation area(Ⅰradar) and uniform deformation area(Ⅱradar) are delineated. The surface deformation rate, cumulative displacement trend and main crack deformation of the whole and local landslide in the revived area are analyzed. At the same time, the engineering geological survey and review are carried out on the spot. It is found that the resurrection and deformation signs of the old landslide are in good agreement with the interpretation results of the SBAS-InSAR technology. It is clear that the SBAS-InSAR technology has broad application prospects in the field of early warning and monitoring of geological disasters in complex mountain areas, and provides new ideas and references for monitoring and early warning similar to old landslides.
Slope instability will not only bring huge losses to industrial and agricultural production, but also pose a great threat to the safety of people's lives. At present, landslides have become one of the three major geological disasters in the world, together with earthquakes and volcanoes. Landslides are caused by a variety of factors such as reservoir water level change. The reservoir water level change induced landslides are particularly concerned. Therefore, it is of great importance to establish a reasonable slope stability analysis method for predicting and preventing landslide hazards. The actual slope instability process often occurs under the coupling effect of various loading factors. However, previous analytical methods such as the limit analysis method focus on the influence of single factor on slope stability and are difficult to reasonably consider coupling application of various factors. Accordingly, they cannot capture the path dependence of the slope stability. In this paper, we establish a model of a soil slope under the combination of top loading and water level change on the basis of the limit analysis method. We assume that the soil below the water level is subject to buoyancy and reduction of cohesion. The effectiveness of the model is verified by the centrifuge test results. The model predictions reveal that the slope stability monotonically decreases with increasing top load, and non-monotonically changes with increasing water level. Therefore, the slope stability is significantly dependent on the coupled loading process. Slope instability will not only bring huge losses to industrial and agricultural production, but also pose a great threat to the safety of people's lives. At present, landslides have become one of the three major geological disasters in the world, together with earthquakes and volcanoes. Landslides are caused by a variety of factors such as reservoir water level change. The reservoir water level change induced landslides are particularly concerned. Therefore, it is of great importance to establish a reasonable slope stability analysis method for predicting and preventing landslide hazards. The actual slope instability process often occurs under the coupling effect of various loading factors. However, previous analytical methods such as the limit analysis method focus on the influence of single factor on slope stability and are difficult to reasonably consider coupling application of various factors. Accordingly, they cannot capture the path dependence of the slope stability. In this paper, we establish a model of a soil slope under the combination of top loading and water level change on the basis of the limit analysis method. We assume that the soil below the water level is subject to buoyancy and reduction of cohesion. The effectiveness of the model is verified by the centrifuge test results. The model predictions reveal that the slope stability monotonically decreases with increasing top load, and non-monotonically changes with increasing water level. Therefore, the slope stability is significantly dependent on the coupled loading process.
Shallow landslide is a common geological hazard in Qinba mountain area. In recent years, the amount of unstable slopes is increasing because of the urbanization. The unstable slope is one of the most serious threatens to the urbanization, because it is very easy changed into shallow landslide with rainfall. It is an urgent to predict the property loss risk caused by unstable slope under different rainfall condition. This paper takes the unstable slopes of Xinglong town as research objective, and assesses the property loss of the buildings affected by the unstable slopes. Firstly, we collect the rainfall data of Xinglong town and fitting these data using Pearson Ⅲ curve to predict the rainfall intensity at different recurrence periods, and then combine rainfall infiltration model and Mote-Carlo method to calculate the probability of unstable slopes changing into landslides under different rainfall conditions. After that, we calculate the vulnerability and the value of objects affected by unstable slopes by means of vulnerability model combined with survey and exploration data. At the end, we use the risk assessment formula proposed by Fell in 2005 to calculate the property loss risk under different rainfall conditions. The results show the following three findings. (1) 245 buildings are affected by unstable slopes, account for 30.4% of the total buildings in Xinglong town. (2) The risk value of the buildings affected by unstable slopes under the rainfall conditions of no rainfall, 65.57mm ·d-1, 72.88mm ·d-1, 85.91mm ·d-1 are 0.228, 0.697, 1.225 and 1.505 million yuan, respectively. (3) More than 55% of the loss is caused by the unstable slopes 1-2, 2-6, 3-5 and 4-3, and the loss caused by these four unstable slopes under the rainfall conditions of no rainfall is 65.57mm ·d-1, 72.88mm ·d-1, 85.91mm ·d-1 over the total loss are 88.33%, 62.9%, 58.64% and 57.54%, respectively. Shallow landslide is a common geological hazard in Qinba mountain area. In recent years, the amount of unstable slopes is increasing because of the urbanization. The unstable slope is one of the most serious threatens to the urbanization, because it is very easy changed into shallow landslide with rainfall. It is an urgent to predict the property loss risk caused by unstable slope under different rainfall condition. This paper takes the unstable slopes of Xinglong town as research objective, and assesses the property loss of the buildings affected by the unstable slopes. Firstly, we collect the rainfall data of Xinglong town and fitting these data using Pearson Ⅲ curve to predict the rainfall intensity at different recurrence periods, and then combine rainfall infiltration model and Mote-Carlo method to calculate the probability of unstable slopes changing into landslides under different rainfall conditions. After that, we calculate the vulnerability and the value of objects affected by unstable slopes by means of vulnerability model combined with survey and exploration data. At the end, we use the risk assessment formula proposed by Fell in 2005 to calculate the property loss risk under different rainfall conditions. The results show the following three findings. (1) 245 buildings are affected by unstable slopes, account for 30.4% of the total buildings in Xinglong town. (2) The risk value of the buildings affected by unstable slopes under the rainfall conditions of no rainfall, 65.57mm ·d-1, 72.88mm ·d-1, 85.91mm ·d-1 are 0.228, 0.697, 1.225 and 1.505 million yuan, respectively. (3) More than 55% of the loss is caused by the unstable slopes 1-2, 2-6, 3-5 and 4-3, and the loss caused by these four unstable slopes under the rainfall conditions of no rainfall is 65.57mm ·d-1, 72.88mm ·d-1, 85.91mm ·d-1 over the total loss are 88.33%, 62.9%, 58.64% and 57.54%, respectively.
Since 1980s, China has built or planned dozens of large-scale interbasin water diversion projects to resolve the issue of water shortage in some regions. The paper collects most data of the long-distance water diversion projects in China, introduces the general situation, establishes a list of the project characteristics, expounds the geological environmental characteristics, draws a distribution map of the projects, discusses the common engineering geological problems. These problems include complex regional geological environmental problems, active tectonics and their influence on tunnels stability, high crustal stress and rock mass stability, water burst caused by high pressure water, debris flow, high ground temperature, harmful gases, slope stability problem, special rock or soil problems, across the river tunnel or large scale aqueduct, mining subsidence and leakage problems, karst problem. The paper points out the matters that should be paid attention to in survey, design and construction. Since 1980s, China has built or planned dozens of large-scale interbasin water diversion projects to resolve the issue of water shortage in some regions. The paper collects most data of the long-distance water diversion projects in China, introduces the general situation, establishes a list of the project characteristics, expounds the geological environmental characteristics, draws a distribution map of the projects, discusses the common engineering geological problems. These problems include complex regional geological environmental problems, active tectonics and their influence on tunnels stability, high crustal stress and rock mass stability, water burst caused by high pressure water, debris flow, high ground temperature, harmful gases, slope stability problem, special rock or soil problems, across the river tunnel or large scale aqueduct, mining subsidence and leakage problems, karst problem. The paper points out the matters that should be paid attention to in survey, design and construction.
The engineering effect of endogenic processes in Himalayan orogen is a frontier problem of basic scientific research in the field of geosciences and engineering. In the longitude direction, based on the tectonic and lithological differences, the Himalayan orogenic belt is divided into 3 parts: Tethys Himalaya, Higher Himalaya and Lesser Himalaya. These studies reveal the universal law that the engineering geological characteristics and disaster effects of the different parts are restricted by endogenic processes. This paper presents the following arguments. Firstly, the rapid uplift of Higher and Lesser Himalaya under the mechanism of compressional collision and orogeny, the earthquakes are mainly thrust fault type and have high earthquake intensity and high frequency. The dominant direction of geostress is close to NE-WS. The terrain develops to a large height difference. The river cuts strongly. The Mountain disaster is serious. Secondly, the Tethys Himalaya belongs to the detachment system and is in a relatively subsidence state. The earthquakes are mainly normal fault type. The seismicity is relatively weak. The geostress direction is close to the E-S. The terrain evolution is trending towards weakening the terrain. And the avalanche disaster is serious. Lastly, the marine glacial landforms, glacial lakes and glacial debris flows are unique to the Higher Himalaya. These may be important issues in controlling the trans-Himalayan railway line scheme. According to the understanding that there are significant differences in the engineering effects of the above parts, this paper puts forward the suggestion of taking the structural division as the railway engineering geological zoning. Taking the traffic corridor of the proposed China-Nepal railway as an example, the engineering geological zoning map is drawn. The research is helpful to advance the theory of Himalayan orogen to the level of engineering application. At the stage of railway large-scale scheme comparison and selection, it provides a new way to obtain information in wide area, high efficiency and low cost. The engineering effect of endogenic processes in Himalayan orogen is a frontier problem of basic scientific research in the field of geosciences and engineering. In the longitude direction, based on the tectonic and lithological differences, the Himalayan orogenic belt is divided into 3 parts: Tethys Himalaya, Higher Himalaya and Lesser Himalaya. These studies reveal the universal law that the engineering geological characteristics and disaster effects of the different parts are restricted by endogenic processes. This paper presents the following arguments. Firstly, the rapid uplift of Higher and Lesser Himalaya under the mechanism of compressional collision and orogeny, the earthquakes are mainly thrust fault type and have high earthquake intensity and high frequency. The dominant direction of geostress is close to NE-WS. The terrain develops to a large height difference. The river cuts strongly. The Mountain disaster is serious. Secondly, the Tethys Himalaya belongs to the detachment system and is in a relatively subsidence state. The earthquakes are mainly normal fault type. The seismicity is relatively weak. The geostress direction is close to the E-S. The terrain evolution is trending towards weakening the terrain. And the avalanche disaster is serious. Lastly, the marine glacial landforms, glacial lakes and glacial debris flows are unique to the Higher Himalaya. These may be important issues in controlling the trans-Himalayan railway line scheme. According to the understanding that there are significant differences in the engineering effects of the above parts, this paper puts forward the suggestion of taking the structural division as the railway engineering geological zoning. Taking the traffic corridor of the proposed China-Nepal railway as an example, the engineering geological zoning map is drawn. The research is helpful to advance the theory of Himalayan orogen to the level of engineering application. At the stage of railway large-scale scheme comparison and selection, it provides a new way to obtain information in wide area, high efficiency and low cost.