2004 Vol. 12, No. 1

论文
The primary objective of urban geology is to investigate and solve the various geological problems associated with resources and the environment in urban construction and development. It meets national needs in various ways during different times of history. The 21st century is an era in which human beings are jointly seeking for sustainable development. Therefore, protection and appropriate utilization of environment and resources have become key strategic issues in the development of China. Based on the knowledge in the development of environmental geology and the concepts of two types of environmental problems, the authors concluded that urban geology should focus on environmental problems encountered in the present expedition of urbanization in China. They include urban environmental geotechnology and geological hazards. In other words, urban geology should focus on urban safety, particularly geotechnical safety. The primary objective of urban geology is to investigate and solve the various geological problems associated with resources and the environment in urban construction and development. It meets national needs in various ways during different times of history. The 21st century is an era in which human beings are jointly seeking for sustainable development. Therefore, protection and appropriate utilization of environment and resources have become key strategic issues in the development of China. Based on the knowledge in the development of environmental geology and the concepts of two types of environmental problems, the authors concluded that urban geology should focus on environmental problems encountered in the present expedition of urbanization in China. They include urban environmental geotechnology and geological hazards. In other words, urban geology should focus on urban safety, particularly geotechnical safety.
From the viewpoint of geology and mechanics, progressive enlargement of cities puts loadings on its geological environment. Actually bearings of the geomaterials in the environment are limited. This paper presents researches on the geological environment and geological hazards associated with the loadings and bearing limits in cities development. More attentions are paid on the potential geologic process with a slow rate in urban areas. Through finding out reactions of the geological media to overlaying additional loadings, this research aims at seeking bearing limit of geomaterials. As a result, the perturbation mechanism of the basement failure, regional ground subsidence, behaving status of aquifers, seismic wave transmission properties, and active faults reoccurrence, etc., are interpreted. From the viewpoint of geology and mechanics, progressive enlargement of cities puts loadings on its geological environment. Actually bearings of the geomaterials in the environment are limited. This paper presents researches on the geological environment and geological hazards associated with the loadings and bearing limits in cities development. More attentions are paid on the potential geologic process with a slow rate in urban areas. Through finding out reactions of the geological media to overlaying additional loadings, this research aims at seeking bearing limit of geomaterials. As a result, the perturbation mechanism of the basement failure, regional ground subsidence, behaving status of aquifers, seismic wave transmission properties, and active faults reoccurrence, etc., are interpreted.
When the stability of a slope engineering project does not be enough high, the slope should be reinforced. In order to make a reasonal reinforcement design, the engineers should firstly find out those locations demanding critical, general, or even no reinforcements. Based on the EGMS methodology, the authors suggest a concept of Degree of Reinforcement Demand (DRD) for slope engineering projects and the relevant assessment procedure. Moreover, an application of the concept to treatment of the shiplock slope of Wuqiangxi Hydropower Station is also described in this paper. When the stability of a slope engineering project does not be enough high, the slope should be reinforced. In order to make a reasonal reinforcement design, the engineers should firstly find out those locations demanding critical, general, or even no reinforcements. Based on the EGMS methodology, the authors suggest a concept of Degree of Reinforcement Demand (DRD) for slope engineering projects and the relevant assessment procedure. Moreover, an application of the concept to treatment of the shiplock slope of Wuqiangxi Hydropower Station is also described in this paper.
On the basis of classification of landslides, in the article the authors systemically put forward the basic geological model for landslides. It is important to consider the influence of every factor and choose the main factor for the model in the research. In different stages of exploration, for different purpose, it is necessary to establish the specific geological model for landslides. The models provide the basis for analysis, calculation, evaluation, monitoring and prediction of landslide deformation and movement and are of benefit to further study of the development of landslides. Finally, it is conduce to improve the research level on landslide. On the basis of classification of landslides, in the article the authors systemically put forward the basic geological model for landslides. It is important to consider the influence of every factor and choose the main factor for the model in the research. In different stages of exploration, for different purpose, it is necessary to establish the specific geological model for landslides. The models provide the basis for analysis, calculation, evaluation, monitoring and prediction of landslide deformation and movement and are of benefit to further study of the development of landslides. Finally, it is conduce to improve the research level on landslide.
Considering the characteristics of underground cavern groups, a stability ranking system was introduced to denote the stability of rock masses surrounding the underground caverns. In this system four factors were used as indices including comprehensive quality level of rock mass, parameters of wedge (volume, shape and stability), displacement and failure zones, and intensity of rock burst. It also provided excavation schemes and supporting measures according to stability ranks. Then a case study was conducted using the ranking system to evaluate the surrounding rock mass stability of an underground cavern group at a planned hydropower station. The results showed that the stability rank of these caverns was classified as Grade II (In other words, the stability was good). The primary failure modes would be local wedge instability and light to moderate rock burst. Considering the characteristics of underground cavern groups, a stability ranking system was introduced to denote the stability of rock masses surrounding the underground caverns. In this system four factors were used as indices including comprehensive quality level of rock mass, parameters of wedge (volume, shape and stability), displacement and failure zones, and intensity of rock burst. It also provided excavation schemes and supporting measures according to stability ranks. Then a case study was conducted using the ranking system to evaluate the surrounding rock mass stability of an underground cavern group at a planned hydropower station. The results showed that the stability rank of these caverns was classified as Grade II (In other words, the stability was good). The primary failure modes would be local wedge instability and light to moderate rock burst.
The permeability experiment of hard rock and soft rock are done under triaxial compressive stress. The permeability, confining pressure, axial pressure, and water pressure are observed. These experiments indicate the permeability coefficient is inversely proportional to increasing effective stress .The permeability coefficient of soft rock is lower than that of hard rock and is more significantly affected by effective stress. The water-resisting capability of the two rocks and the mechanism for water inrush through the cracks in rock mass are analyzed according to the experiments. The permeability experiment of hard rock and soft rock are done under triaxial compressive stress. The permeability, confining pressure, axial pressure, and water pressure are observed. These experiments indicate the permeability coefficient is inversely proportional to increasing effective stress .The permeability coefficient of soft rock is lower than that of hard rock and is more significantly affected by effective stress. The water-resisting capability of the two rocks and the mechanism for water inrush through the cracks in rock mass are analyzed according to the experiments.
Based on the distribution characteristics and formation background, a regionalization of red beds in China is suggested, such as red beds in northwest, southwest, southeast and south-central China and parts of Xizang and North China. The study was focussed on the red beds in Sichuan-Yunnan region, representative of southwest China and the red beds in Gansu, the representative of northwest China, the geologic environment characteristics of the red beds, such as the geostructural characteristics, geomorphic characteristics, climatic environment characteristics etc. were studied. According to the geologic environment characteristics, the red beds in Sichuan-Yunnan region are zoned into those in Sichuan basin, Xichang Dianzhong, Dianxi and Gansu. Based on the distribution characteristics and formation background, a regionalization of red beds in China is suggested, such as red beds in northwest, southwest, southeast and south-central China and parts of Xizang and North China. The study was focussed on the red beds in Sichuan-Yunnan region, representative of southwest China and the red beds in Gansu, the representative of northwest China, the geologic environment characteristics of the red beds, such as the geostructural characteristics, geomorphic characteristics, climatic environment characteristics etc. were studied. According to the geologic environment characteristics, the red beds in Sichuan-Yunnan region are zoned into those in Sichuan basin, Xichang Dianzhong, Dianxi and Gansu.
The overburden in the mining influencing zone is often composed of red strata and coal beds in many coalmines. This paper evaluated the failure of the overburden and the establishment of safety pillars under water body for the coal seam No.3 of Permian System in the Taiping coal mine, Shandong Province. By evaluating hydrogeological condition of the Quaternary sediments and engineering geological characteristics of the compositely structured overburden with red strata and coal beds, its failure conditions during coal mining were characterized. As a result, the height of safety pillars was determined, which has been confirmed by the field tests and assured that no water-intrusion hazard or sand rush would occur. The overburden in the mining influencing zone is often composed of red strata and coal beds in many coalmines. This paper evaluated the failure of the overburden and the establishment of safety pillars under water body for the coal seam No.3 of Permian System in the Taiping coal mine, Shandong Province. By evaluating hydrogeological condition of the Quaternary sediments and engineering geological characteristics of the compositely structured overburden with red strata and coal beds, its failure conditions during coal mining were characterized. As a result, the height of safety pillars was determined, which has been confirmed by the field tests and assured that no water-intrusion hazard or sand rush would occur.
The underground erosion and disintegration produced by the activity of ground water will result in formation of soil caves. The vaccum sucking will be helpful for soil cave development. The stress distribution around the soil cave will changed due to variation of groundwater level, then the soil mass around the cave may plastically fail and the soil cave may enlarge or collapse. The underground erosion and disintegration produced by the activity of ground water will result in formation of soil caves. The vaccum sucking will be helpful for soil cave development. The stress distribution around the soil cave will changed due to variation of groundwater level, then the soil mass around the cave may plastically fail and the soil cave may enlarge or collapse.
There is a kind of black geological material with loose structure, complex components, extreme sensitivity to water and inferior engineering properties in the southern region of Daqing City. It has all the inferior properties of collapsible soil, organic soil, alkali soil, dispersive soil and other special soils. On the basis of field investigation, in-situ tests and laboratory tests, this paper systemically characterized and analyzed the black soil including the field identification, component structure, physical and mechanical properties, bearing capacity, collapsible performance, and stratum age. As a result of a comprehensive comparison, the soil is named as collapsible black soil. There is a kind of black geological material with loose structure, complex components, extreme sensitivity to water and inferior engineering properties in the southern region of Daqing City. It has all the inferior properties of collapsible soil, organic soil, alkali soil, dispersive soil and other special soils. On the basis of field investigation, in-situ tests and laboratory tests, this paper systemically characterized and analyzed the black soil including the field identification, component structure, physical and mechanical properties, bearing capacity, collapsible performance, and stratum age. As a result of a comprehensive comparison, the soil is named as collapsible black soil.
Motuo County of Tibet is the only county without a highway in China. Motuo is located on the sewing-belt between the Indian Ocean block and the Europe-Asia block. It is the museum of geological hazards. Because of the constraint of the Himalayas, limited accessibility and the difficulty weather conditions, it is not practical to adopt the conventional ways in reconnaissance of the geological hazards along the potential route for the highway to be constructed. Hence the Landsat ETM+, Ikonos-2 and aero-photograph were adopted to fill up the gap of geological information in this area. The geological hazards and their distributions in the area were then characterized using multi-level geological remote sensing analysis, which provided guidelines in the identification of hazardous geological masses along the highway route. It proved to be a good method for the selection of the best route scheme of the Motuo road. Motuo County of Tibet is the only county without a highway in China. Motuo is located on the sewing-belt between the Indian Ocean block and the Europe-Asia block. It is the museum of geological hazards. Because of the constraint of the Himalayas, limited accessibility and the difficulty weather conditions, it is not practical to adopt the conventional ways in reconnaissance of the geological hazards along the potential route for the highway to be constructed. Hence the Landsat ETM+, Ikonos-2 and aero-photograph were adopted to fill up the gap of geological information in this area. The geological hazards and their distributions in the area were then characterized using multi-level geological remote sensing analysis, which provided guidelines in the identification of hazardous geological masses along the highway route. It proved to be a good method for the selection of the best route scheme of the Motuo road.
A new simpler method is presented for evaluating the earthquake-induced permanent displacements of sliding body based on residual pushing force method as well as Newmark's method (1965). At the same time, pore pressure increment caused by dynamic force is considered. Then this method is applied to a case, in which our prediction result is very close to that obtained by using numerical method, but the value obtained by former methed is slightly higher than that by numerical method. A new simpler method is presented for evaluating the earthquake-induced permanent displacements of sliding body based on residual pushing force method as well as Newmark's method (1965). At the same time, pore pressure increment caused by dynamic force is considered. Then this method is applied to a case, in which our prediction result is very close to that obtained by using numerical method, but the value obtained by former methed is slightly higher than that by numerical method.
Based on soil nail axial force and slope displacement testing, a 3-D soil nailing support numerical model is constructed and the slope displacement, soil nail axial force, plastic displacement are deeply discussed in this paper.Most meaningful conclusions are drawn: soil nail and soil mass form a whole supporting system through their interaction; foundation pit in stability is not due to soil mass failure or soil nail failure, but is due to the instability of whole supporting system; the supporting system is formed by soil nail bearing partial force and stress transferring and diffusing. These are the essence of the soil nail support. Based on soil nail axial force and slope displacement testing, a 3-D soil nailing support numerical model is constructed and the slope displacement, soil nail axial force, plastic displacement are deeply discussed in this paper.Most meaningful conclusions are drawn: soil nail and soil mass form a whole supporting system through their interaction; foundation pit in stability is not due to soil mass failure or soil nail failure, but is due to the instability of whole supporting system; the supporting system is formed by soil nail bearing partial force and stress transferring and diffusing. These are the essence of the soil nail support.
surface and sub-surface samples of expansive soils was collected in the Handan-Yongnian area, Nanyang district, Pingdingshan area along the middle line of the Project of Diverting Water from South to North and in Xiangfan area and Zhongxiang district of Jingmeng City. Clay mineral composition and smectite content were determined by using XRD and dye absorption methods. Meanwhile,such indices as liquid limit, plastic limit, specific surface, clay particles and colloid particles, free swell ratio were quantitatively measured. Study on smectite content and the indices for discrimination swell potential indicates that smectite content is a principal factor controlling the swell potential. Of course, the measurement errors, mainly the error in smectite content, are also the second factors influencing swell potential gradation. The swell potential graded by using Seeds method is higher by 1 to 2 levers than that by using the suggested standard in the paper. The relationship between smectite content and indices is linear, logarithmic or exponential and provides a basis for expansive soil remote sensing in relation with the diagnostic absorption features of clay minerals. surface and sub-surface samples of expansive soils was collected in the Handan-Yongnian area, Nanyang district, Pingdingshan area along the middle line of the Project of Diverting Water from South to North and in Xiangfan area and Zhongxiang district of Jingmeng City. Clay mineral composition and smectite content were determined by using XRD and dye absorption methods. Meanwhile,such indices as liquid limit, plastic limit, specific surface, clay particles and colloid particles, free swell ratio were quantitatively measured. Study on smectite content and the indices for discrimination swell potential indicates that smectite content is a principal factor controlling the swell potential. Of course, the measurement errors, mainly the error in smectite content, are also the second factors influencing swell potential gradation. The swell potential graded by using Seeds method is higher by 1 to 2 levers than that by using the suggested standard in the paper. The relationship between smectite content and indices is linear, logarithmic or exponential and provides a basis for expansive soil remote sensing in relation with the diagnostic absorption features of clay minerals.
The rock mass unloading is one of engineering-geological problems in construction of hydroelectric projects. This paper introduces the background and formation mechanism for the rock mass unloading, the common characteristics of unloded rockmass and several methods for discriminating the unloaded zone. Considering the numbers and opening degree of joints in rock mass gradually reducing from the surface to depth, basing on field investigation data of Indo sinian granite on a high slope of hydroelectric station on the upstream of Yellow River, the rock mass unloading zone is discriminated in accordance with amounts and opening degree of joints in combination with rock mass structure and its engineering properties. This result provides a reference for other slope engineering. The rock mass unloading is one of engineering-geological problems in construction of hydroelectric projects. This paper introduces the background and formation mechanism for the rock mass unloading, the common characteristics of unloded rockmass and several methods for discriminating the unloaded zone. Considering the numbers and opening degree of joints in rock mass gradually reducing from the surface to depth, basing on field investigation data of Indo sinian granite on a high slope of hydroelectric station on the upstream of Yellow River, the rock mass unloading zone is discriminated in accordance with amounts and opening degree of joints in combination with rock mass structure and its engineering properties. This result provides a reference for other slope engineering.
The level of seismic effect and earthquake risk is rather low, and far intense earthquake can not be a main geological problem with engineerng projects in Wuhan area, but the earthquake resistance measures must be considerded in constructing urban lifeline and superior buildings. With the unceasing social-economic development in Wuhan, the influence of earthquake becomes gradually a rather important factor in engineering-geological environment evaluation. After the research on seismic ground motion attenuation regularities we make an evaluation of earthquake risk and analyze the dynamic parameters of soil layers in Wuhan area, and then point out there exist two main types of ground failures by earthquake in Wuhan area: liquefaction of sandy soil and collapse of soft soil layer, and their possible spatial distribution is put forward. The level of seismic effect and earthquake risk is rather low, and far intense earthquake can not be a main geological problem with engineerng projects in Wuhan area, but the earthquake resistance measures must be considerded in constructing urban lifeline and superior buildings. With the unceasing social-economic development in Wuhan, the influence of earthquake becomes gradually a rather important factor in engineering-geological environment evaluation. After the research on seismic ground motion attenuation regularities we make an evaluation of earthquake risk and analyze the dynamic parameters of soil layers in Wuhan area, and then point out there exist two main types of ground failures by earthquake in Wuhan area: liquefaction of sandy soil and collapse of soft soil layer, and their possible spatial distribution is put forward.
The current anti-offset design usually adopts the deterministic method of the maximum outburst offset on the fault, which cannot meet requirements of risk design for prevention of earthquake disasters. By combining the location of the maximum offset, the distribution of the offset along two sides of the maximum offset, and the recurrence model of strong earthquakes pertaining to the ground offset, authors introduced a method of probabilistic assessment to evaluate potential ground offset along the strike-slip active fault. Taking the Songlinkou-Qianning segment on Xianshuihe strike-slip fault zone as an example, the quantitative evaluation of the risk of potential offset in future 100a was conducted. The potential offsets along the active fault were assessed under different exceeding probabilistic levels. Such results could provide scientific guidelines for the risk assessment of the anti-offset of linear engineering structures across the active fault. The current anti-offset design usually adopts the deterministic method of the maximum outburst offset on the fault, which cannot meet requirements of risk design for prevention of earthquake disasters. By combining the location of the maximum offset, the distribution of the offset along two sides of the maximum offset, and the recurrence model of strong earthquakes pertaining to the ground offset, authors introduced a method of probabilistic assessment to evaluate potential ground offset along the strike-slip active fault. Taking the Songlinkou-Qianning segment on Xianshuihe strike-slip fault zone as an example, the quantitative evaluation of the risk of potential offset in future 100a was conducted. The potential offsets along the active fault were assessed under different exceeding probabilistic levels. Such results could provide scientific guidelines for the risk assessment of the anti-offset of linear engineering structures across the active fault.
Anti-sliding pile are used to stabilize slopes and to control landslide for a long history. It is because of the soil arching effect between the piles that can work effectively. According to the limit equilibrium of the soil mass,the horizontal soil arching effect between the cylindrical anti-sliding piles in the earth is studied and the formula for largest spacing between the piles is proposed. Then, through a case study, the physical meanings and the feasibility of the largest spacing between the piles are discussed. Then the suitable spacing between the piles is proposed in consideration of the soil arching effect. Finally, Some useful suggestions for the slope engineering designing are also proposed in the paper. Anti-sliding pile are used to stabilize slopes and to control landslide for a long history. It is because of the soil arching effect between the piles that can work effectively. According to the limit equilibrium of the soil mass,the horizontal soil arching effect between the cylindrical anti-sliding piles in the earth is studied and the formula for largest spacing between the piles is proposed. Then, through a case study, the physical meanings and the feasibility of the largest spacing between the piles are discussed. Then the suitable spacing between the piles is proposed in consideration of the soil arching effect. Finally, Some useful suggestions for the slope engineering designing are also proposed in the paper.
A comparative study of meso-failure mechanisms of sandstone under successive loading and unloading conditions is made by using a special triaxial loading equipment corollay to a CT equipment. The CT images obtained show that the unloading failure is explosive, resulting in a dilatancy more than that of succesive loading failure. A comparative study of meso-failure mechanisms of sandstone under successive loading and unloading conditions is made by using a special triaxial loading equipment corollay to a CT equipment. The CT images obtained show that the unloading failure is explosive, resulting in a dilatancy more than that of succesive loading failure.
This paper discussed the changes in the static triaxial strength of silty clay and clay mixed with lime, cement and fly-ash at different mixture ratio. The relationship between mixture ratio and strength of different mixtures was obtained through analysis and comparison.Such results could provide a reliable guideline for design, construction and maintenance of the subsoil to assure the requirements be met for the subgrade bed of high speed railway and embankment fillings below the subgrade bed. This paper discussed the changes in the static triaxial strength of silty clay and clay mixed with lime, cement and fly-ash at different mixture ratio. The relationship between mixture ratio and strength of different mixtures was obtained through analysis and comparison.Such results could provide a reliable guideline for design, construction and maintenance of the subsoil to assure the requirements be met for the subgrade bed of high speed railway and embankment fillings below the subgrade bed.