2004 Vol. 12, No. 4

论文
This paper presents the state of the art of engineering geology in China. The author also provides perspectives for its future development. This paper presents the state of the art of engineering geology in China. The author also provides perspectives for its future development.
Similarities and differences between engineering geology and geotechnical engineering are discussed in details. It is concluded that engineering geology is the basis of geotechnical engineering, while geotechnical engineering is an extension of engineering geology. Similarities and differences between engineering geology and geotechnical engineering are discussed in details. It is concluded that engineering geology is the basis of geotechnical engineering, while geotechnical engineering is an extension of engineering geology.
Potential earthquake regions are the hypocenter areas of future destructive earthquakes that might be of either near field type or direct-underground one. The characteristics of destruction and ground motion of the earthquakes in these regions are similar to those of meizoseismal areas of past earthquakes. The existing data and associated research of some recent earthquakes occurred in China and abroad indicate that: direct-underground earthquakes not only demonstrate very high peak accelerations, but also show ratios of peak vertical acceleration to peak horizontal one that are quite different from those of far field earthquakes. In this paper, authors also discuss safety issues of important engineering projects located in potential earthquake prone regions in the following aspects: rock mass soil failure at meizoseismal areas, ground motion characteristics and seismo-geological hazards etc. Potential earthquake regions are the hypocenter areas of future destructive earthquakes that might be of either near field type or direct-underground one. The characteristics of destruction and ground motion of the earthquakes in these regions are similar to those of meizoseismal areas of past earthquakes. The existing data and associated research of some recent earthquakes occurred in China and abroad indicate that: direct-underground earthquakes not only demonstrate very high peak accelerations, but also show ratios of peak vertical acceleration to peak horizontal one that are quite different from those of far field earthquakes. In this paper, authors also discuss safety issues of important engineering projects located in potential earthquake prone regions in the following aspects: rock mass soil failure at meizoseismal areas, ground motion characteristics and seismo-geological hazards etc.
The South-North Water Diversion Project (SNWDP) is a world-attracted giant trans-basin water transfer project, which consists of three routes: the east route, the central route and the west route. Due to its large coverage that crosses several river basins, engineering geological conditions of the SNWDP are characterized by diversity and complexity. In particular, various and very complicated engineering geological problems, which are rarely encountered both in China and abroad, exist along the west route, due to its unique geographic location, climate, tectonic settings and scale. As a result, the geological investigation is a very difficult task. Properly solving engineering geological problems encountered in the SNWDP will not only meet the basic requirements for the timely completion of the project, but also advance the engineering geosciences and relevant technologies as well. The South-North Water Diversion Project (SNWDP) is a world-attracted giant trans-basin water transfer project, which consists of three routes: the east route, the central route and the west route. Due to its large coverage that crosses several river basins, engineering geological conditions of the SNWDP are characterized by diversity and complexity. In particular, various and very complicated engineering geological problems, which are rarely encountered both in China and abroad, exist along the west route, due to its unique geographic location, climate, tectonic settings and scale. As a result, the geological investigation is a very difficult task. Properly solving engineering geological problems encountered in the SNWDP will not only meet the basic requirements for the timely completion of the project, but also advance the engineering geosciences and relevant technologies as well.
This paper is an academic summary of the 7th National Conference of Engineering Geology held in Kun-ming from October 21 through 23. The author provides an overview based on the keynote speeches and papers presented at this conference, which demonstrate the state of art of Engineering Geology in China and advances in its different research areas. This paper is an academic summary of the 7th National Conference of Engineering Geology held in Kun-ming from October 21 through 23. The author provides an overview based on the keynote speeches and papers presented at this conference, which demonstrate the state of art of Engineering Geology in China and advances in its different research areas.
River terraces were developed and preserved well in the outlet of Heishan Gorge of the Yellow River, Northeast margin of the Tibetan Plateau. The terraces not only documented the uplift history of northeast part of the Tibetan Plateau since Quaternary, but its characteristics and distribution also reflect the active features of F 8(7)and F 201 faults. Detailed studies show that there are seven terraces preserved to the south of F 8(7) fault but only five terraces preserved to the north of F 8(7) fault and to the north of F 201 fault. All the terraces are pedestal terrace. The frontier lines of the TerraceⅠ,Ⅱ and Ⅲ is continuous, but the width of Terrace Ⅲ increase sharply across the F 8(7) and sinistral displacement of the frontier line of Terrace Ⅳ and,Ⅴ amounts to 150 meter. The width of TerraceⅡ changes from 200 meter to 710 meter across F 201, and the frontier line of the terrace Ⅲ, Ⅳ andⅤ displaced to 400 meter across F 201. Those changes of width and displacement of the terraces documented F 201 and F 8(7) fault activity since Pleistocene, which provide us with important data for evaluation of fault activity. River terraces were developed and preserved well in the outlet of Heishan Gorge of the Yellow River, Northeast margin of the Tibetan Plateau. The terraces not only documented the uplift history of northeast part of the Tibetan Plateau since Quaternary, but its characteristics and distribution also reflect the active features of F 8(7)and F 201 faults. Detailed studies show that there are seven terraces preserved to the south of F 8(7) fault but only five terraces preserved to the north of F 8(7) fault and to the north of F 201 fault. All the terraces are pedestal terrace. The frontier lines of the TerraceⅠ,Ⅱ and Ⅲ is continuous, but the width of Terrace Ⅲ increase sharply across the F 8(7) and sinistral displacement of the frontier line of Terrace Ⅳ and,Ⅴ amounts to 150 meter. The width of TerraceⅡ changes from 200 meter to 710 meter across F 201, and the frontier line of the terrace Ⅲ, Ⅳ andⅤ displaced to 400 meter across F 201. Those changes of width and displacement of the terraces documented F 201 and F 8(7) fault activity since Pleistocene, which provide us with important data for evaluation of fault activity.
This paper first characterizes geological conditions including stratigraphic lithology, hydrology and tectonic structures at the Pingzhai damsite. The authors then analyze distribution of karst caves at the left bank of the Pingzhai dam site based on morphology of karst. The results indicate that depressions, corroded funnels and sinkholes occur in a band distribution horizontally, and multiple stratifications vertically. The distribution of karst caves has a strong orientation in three dimensions. The following results are also obtained: (1) The purer the carbonate is and the thicker the bedding is, the more karst caves develop; (2) The folds control not only the direction of the karst development, but also the location, scale and configuration of karst caves; (3) The intensity and the extension of fracture development control the intensity and extension of karst development. At the end, the authors assess the potential development of karst caves at the left bank and its influence on the leakage and instability of the dam site: (1) The karst will develop extensively at the bank surface, but not inside the bank; (2) The potential for large cave development near the dam axis is very small; (3) The potential for karst development below the river bed is also very small. This paper first characterizes geological conditions including stratigraphic lithology, hydrology and tectonic structures at the Pingzhai damsite. The authors then analyze distribution of karst caves at the left bank of the Pingzhai dam site based on morphology of karst. The results indicate that depressions, corroded funnels and sinkholes occur in a band distribution horizontally, and multiple stratifications vertically. The distribution of karst caves has a strong orientation in three dimensions. The following results are also obtained: (1) The purer the carbonate is and the thicker the bedding is, the more karst caves develop; (2) The folds control not only the direction of the karst development, but also the location, scale and configuration of karst caves; (3) The intensity and the extension of fracture development control the intensity and extension of karst development. At the end, the authors assess the potential development of karst caves at the left bank and its influence on the leakage and instability of the dam site: (1) The karst will develop extensively at the bank surface, but not inside the bank; (2) The potential for large cave development near the dam axis is very small; (3) The potential for karst development below the river bed is also very small.
The main tower of a sea-crossing rope suspension bridge with a 1,650 meter span lies on an island. The thin mountain intersected by faults and other structural fissures result in low intactness of rock mass. Based on field geological investigations, the authors made a systematic analysis of the structure load and wind load and the slope stability. Results show that the slope is stable as a whole, but some unstable rock masses exist near the surface. To enhance stability of near surface rock masses, reinforcement measures are recommended. The main tower of a sea-crossing rope suspension bridge with a 1,650 meter span lies on an island. The thin mountain intersected by faults and other structural fissures result in low intactness of rock mass. Based on field geological investigations, the authors made a systematic analysis of the structure load and wind load and the slope stability. Results show that the slope is stable as a whole, but some unstable rock masses exist near the surface. To enhance stability of near surface rock masses, reinforcement measures are recommended.
This paper describes the sedimentation characteristics of the Jurassic sliding-prone stratum in the Three Gorges reservoir area based on analyses of lithofacies paleogeography and evolution of the sedimentation environment. The authors then assess their influence on physical and mechanical properties of rock in the Three Gorges reservoir area. As such, sedimentologic causes for the frequent occurrence of geologic hazards, especially landslides in the Three Gorges reservoir area, are identified. This paper describes the sedimentation characteristics of the Jurassic sliding-prone stratum in the Three Gorges reservoir area based on analyses of lithofacies paleogeography and evolution of the sedimentation environment. The authors then assess their influence on physical and mechanical properties of rock in the Three Gorges reservoir area. As such, sedimentologic causes for the frequent occurrence of geologic hazards, especially landslides in the Three Gorges reservoir area, are identified.
The geological conditions of the Yangjialing landslide are complicated, and it has seriously affected the national highway. This paper presents various factors that influence the landslide stability followed with their respective sensitivity analysis. Results indicate that many factors affect landslide stability, including the gravity density of the rock-soil, values of c and of the slipband, values of c and of the slide-body, the dynamic of groundwater in the landslide body, earthquake activities and others. Among them, the anti-shearing strength indices (c、 ) of the slipband, groundwater and earthquake activities are the most sensitive factors, which may trigger the landslide. At the end, an optimum reinforce azimuth is established for landslide control based on the relationship between the stability coefficient, the reinforce force and the azimuth of the slope surface, which provides a guideline for the integrated control of the landslide. The geological conditions of the Yangjialing landslide are complicated, and it has seriously affected the national highway. This paper presents various factors that influence the landslide stability followed with their respective sensitivity analysis. Results indicate that many factors affect landslide stability, including the gravity density of the rock-soil, values of c and of the slipband, values of c and of the slide-body, the dynamic of groundwater in the landslide body, earthquake activities and others. Among them, the anti-shearing strength indices (c、 ) of the slipband, groundwater and earthquake activities are the most sensitive factors, which may trigger the landslide. At the end, an optimum reinforce azimuth is established for landslide control based on the relationship between the stability coefficient, the reinforce force and the azimuth of the slope surface, which provides a guideline for the integrated control of the landslide.
This paper presents analytical results of composition and microstructure of the discrete structural surrounding rock mass in a low geostress region. Rock samples, taken from the surrounding rock mass at different locations of the underground excavation for a water conveyance project, are analyzed for chemical composition, average percentage of content, and microstructures by using electron diffraction and electron-scan microscope. The micro-deformation of the rock is then characterized, thus providing guidelines for further study for macro deformation, failure and stability of rock masses in the low geostress region. This paper presents analytical results of composition and microstructure of the discrete structural surrounding rock mass in a low geostress region. Rock samples, taken from the surrounding rock mass at different locations of the underground excavation for a water conveyance project, are analyzed for chemical composition, average percentage of content, and microstructures by using electron diffraction and electron-scan microscope. The micro-deformation of the rock is then characterized, thus providing guidelines for further study for macro deformation, failure and stability of rock masses in the low geostress region.
This paper reviews the development of research in regional crust stability and evaluates existing theories for regional stability assessment. The authors emphasize that regional stability assessment should be conducted by incorporating them with engineering projects, which translates the site assessment, site utilization into geological engineering design. The development of theories for regional stability assessment should be established on the basis of the advanced frontiers of earth science, such as Dynamics of Lithosphere and Dynamics of Continental Plate. As for methodology, geological disasters and their impacts on engineering structures should be characterized by coupling analysis of endogenic and exogenic geological processes. As a result, it is anticipated that the system analysis and quantitative assessment of regional crust stability can be achieved by establishing a unified dynamics model of geological disasters. This paper reviews the development of research in regional crust stability and evaluates existing theories for regional stability assessment. The authors emphasize that regional stability assessment should be conducted by incorporating them with engineering projects, which translates the site assessment, site utilization into geological engineering design. The development of theories for regional stability assessment should be established on the basis of the advanced frontiers of earth science, such as Dynamics of Lithosphere and Dynamics of Continental Plate. As for methodology, geological disasters and their impacts on engineering structures should be characterized by coupling analysis of endogenic and exogenic geological processes. As a result, it is anticipated that the system analysis and quantitative assessment of regional crust stability can be achieved by establishing a unified dynamics model of geological disasters.
This paper presents a modification to the Terzaghis bearing capacity equation, which is based on the rigid-plastic theory, based on data from nineteen deep plate loading tests. A new equation is derived for assessing the pile-tip bearing capacity of the Tertiary mudstone in Guangxi. This paper presents a modification to the Terzaghis bearing capacity equation, which is based on the rigid-plastic theory, based on data from nineteen deep plate loading tests. A new equation is derived for assessing the pile-tip bearing capacity of the Tertiary mudstone in Guangxi.
This paper evaluates both suitability and advantages of the AS series high-performance stabilizer used in reinforcement of soft soil foundations in Tianjin by comparing its performance against common cement-reinforced soils. The paper also presents a complete set of construction design parameters to be used for design and implementation of reinforcement of soft soil foundations. This paper evaluates both suitability and advantages of the AS series high-performance stabilizer used in reinforcement of soft soil foundations in Tianjin by comparing its performance against common cement-reinforced soils. The paper also presents a complete set of construction design parameters to be used for design and implementation of reinforcement of soft soil foundations.
In this paper the authors first describe geologic conditions of Zaolin landslide. The shear strength of the sliding plane at Zaolin Landslide is then obtained based on laboratory tests, expert experiences and back analysis of the stability of the landslide. A reinforcement plan using anti-slide piles with pre-stressed anchor wires is suggested. Its design method and construction techniques are discussed in detail. Subsequent monitoring data confirmed the success of the suggested reinforcement plan. In this paper the authors first describe geologic conditions of Zaolin landslide. The shear strength of the sliding plane at Zaolin Landslide is then obtained based on laboratory tests, expert experiences and back analysis of the stability of the landslide. A reinforcement plan using anti-slide piles with pre-stressed anchor wires is suggested. Its design method and construction techniques are discussed in detail. Subsequent monitoring data confirmed the success of the suggested reinforcement plan.
Brillouin Optical Time-Domain Reflectometer (BOTDR) is a newly developed distributed measuring technique for strains. In this paper, the merits and the basic measurement principle of BOTDR is presented. The feasibility and advantages of the distributed strain monitoring of structures in geotechnical engineering are demonstrated by a case study for strain monitoring in a tunnel. At the end, several key issues for applications of BOTDR are discussed, including enhancement of spatial resolution, layout of the sensing optical fiber and the health monitoring and damage diagnosis. Brillouin Optical Time-Domain Reflectometer (BOTDR) is a newly developed distributed measuring technique for strains. In this paper, the merits and the basic measurement principle of BOTDR is presented. The feasibility and advantages of the distributed strain monitoring of structures in geotechnical engineering are demonstrated by a case study for strain monitoring in a tunnel. At the end, several key issues for applications of BOTDR are discussed, including enhancement of spatial resolution, layout of the sensing optical fiber and the health monitoring and damage diagnosis.
Through use of the stronger nonlinear mapping and learning ability of the back propagation neural network, the authors develop a new artificial neural network model to predict the settlement of highway foundation. This model avoids the errors caused by artificial factors during calculation since the model is established using all in-situ observation data. The results show that the model simulation matches well with in-situ observation of the highway foundation settlement, which demonstrates its applicability in the engineering practice. Through use of the stronger nonlinear mapping and learning ability of the back propagation neural network, the authors develop a new artificial neural network model to predict the settlement of highway foundation. This model avoids the errors caused by artificial factors during calculation since the model is established using all in-situ observation data. The results show that the model simulation matches well with in-situ observation of the highway foundation settlement, which demonstrates its applicability in the engineering practice.
Based on the fracture mechanics theory under confining pressure conditions, the authors test rock fracture toughness using the thick-wall cylinder specimens with double-wing fractures and different clay contents under various confining pressures. The authors then use the finite element model to interpret the toughness results. The regression analysis based on a number of experiments indicates that the relationships of fracture toughness with confining pressure and shale contents are linear with small errors. The experimental procedures and interpreting method presented in this paper assure a better accuracy for determination of fracture toughness for hydraulic fracturing than that obtained from experiments without confining pressures, and are thus favorable for improvement of hydraulic fracturing performance. Based on the fracture mechanics theory under confining pressure conditions, the authors test rock fracture toughness using the thick-wall cylinder specimens with double-wing fractures and different clay contents under various confining pressures. The authors then use the finite element model to interpret the toughness results. The regression analysis based on a number of experiments indicates that the relationships of fracture toughness with confining pressure and shale contents are linear with small errors. The experimental procedures and interpreting method presented in this paper assure a better accuracy for determination of fracture toughness for hydraulic fracturing than that obtained from experiments without confining pressures, and are thus favorable for improvement of hydraulic fracturing performance.
Most landslides are associated with changes in groundwater levels. Dynamics of groundwater sometimes dictates stability of the landslides. Therefore, it is very important to understand how different factors and engineering mitigation measures affect groundwater flow during treatment of a landslide so that an appropriate measure can be selected. A numerical simulation case study is used to demonstrate the drainage effects on underground tunnel, the groundwater table changes caused by surface water infiltration and anti-sliding piles settings. The simulation results provide an insight into effects of different factors on the seepage field in a slope, which can help optimize design of treatment measures for a landslide. Most landslides are associated with changes in groundwater levels. Dynamics of groundwater sometimes dictates stability of the landslides. Therefore, it is very important to understand how different factors and engineering mitigation measures affect groundwater flow during treatment of a landslide so that an appropriate measure can be selected. A numerical simulation case study is used to demonstrate the drainage effects on underground tunnel, the groundwater table changes caused by surface water infiltration and anti-sliding piles settings. The simulation results provide an insight into effects of different factors on the seepage field in a slope, which can help optimize design of treatment measures for a landslide.