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Editor Work2000 Vol. 8, No. 2
Previous Issue
2000, 8(2): 131-135.
Abstract
117KB
The complex geolgical environment and geomorphologic features on the middle and lower reaches of Jinshajiang River are discussed. They are the well developed active structures, intense and frequent seismic activities, and seldom seen super high and steep slopes in hydroelectric project areas in the world, etc. In process and after the constructions of high dams and reservoirs with large storage capacity, some potential problems related to the slopes are analysed, such as high stress in the slope masses, seismic response and weakening of rockmass strength, reinforcement technique and cost, as well as the effect of flood discharge with high energy and large flow capacity on the slope stability, etc. Systematic pre study of these problems is very important for selection of dam site, lay out of engineering project, timelimit, cost and safety, etc.
The complex geolgical environment and geomorphologic features on the middle and lower reaches of Jinshajiang River are discussed. They are the well developed active structures, intense and frequent seismic activities, and seldom seen super high and steep slopes in hydroelectric project areas in the world, etc. In process and after the constructions of high dams and reservoirs with large storage capacity, some potential problems related to the slopes are analysed, such as high stress in the slope masses, seismic response and weakening of rockmass strength, reinforcement technique and cost, as well as the effect of flood discharge with high energy and large flow capacity on the slope stability, etc. Systematic pre study of these problems is very important for selection of dam site, lay out of engineering project, timelimit, cost and safety, etc.
2000, 8(2): 136-141.
RelationshIp between landslides and neotectonism in reservoir area of Three-Gorges Project on Yangtze River were examined. The neotectonism exhibits well staged character reflecting in alternate crustal uplifting and relatively stable periods and alternate faulting and seismo-active periods.The sliding events of landslides are also staged and are well correlated with the neotectonic stages. The occurrence times of landslides coincide with neotectonic activity stages. From the results we can conclude that the neotectonic factor plays an important role in sliding of landslides in the Three-Gorges area. The seismo-active periodicity indicates that the neotectonism has entered into a quiet stage since 1980s. The internal factors for structural activities may be comparatively insignificant for the occurrence of landslides in a relatively long-term future. It is suggested that the human activity may be a main factor causing landslide to occur. This must be taken into adequate consideration in the reservoir area of the Three-Gorges Project on Yangtze River.
RelationshIp between landslides and neotectonism in reservoir area of Three-Gorges Project on Yangtze River were examined. The neotectonism exhibits well staged character reflecting in alternate crustal uplifting and relatively stable periods and alternate faulting and seismo-active periods.The sliding events of landslides are also staged and are well correlated with the neotectonic stages. The occurrence times of landslides coincide with neotectonic activity stages. From the results we can conclude that the neotectonic factor plays an important role in sliding of landslides in the Three-Gorges area. The seismo-active periodicity indicates that the neotectonism has entered into a quiet stage since 1980s. The internal factors for structural activities may be comparatively insignificant for the occurrence of landslides in a relatively long-term future. It is suggested that the human activity may be a main factor causing landslide to occur. This must be taken into adequate consideration in the reservoir area of the Three-Gorges Project on Yangtze River.
2000, 8(2): 142-147.
Based on the coupling mechanism of seepage field with displacement field, the effect of seepage on the displacement of high rock slope in a certain large boat gate project is studied in this paper. By use of finite element method, the seepage field and displacement field are calculated. The result shows that there is a significant effect of the seepage force on the stability of the rock slope. It indicates that a correct consideration of seepage force in analysis of high rock slope stability is very important.
Based on the coupling mechanism of seepage field with displacement field, the effect of seepage on the displacement of high rock slope in a certain large boat gate project is studied in this paper. By use of finite element method, the seepage field and displacement field are calculated. The result shows that there is a significant effect of the seepage force on the stability of the rock slope. It indicates that a correct consideration of seepage force in analysis of high rock slope stability is very important.
2000, 8(2): 148-153.
A lot of facts from field investigations show that a time-dependent deformation of a high rock slope could occur before its instability. Accompanied with this process, a potential slIp surface develops gradually in the slope, and finally cut through due to progressive failure along it or some triggering factors. In this paper, the phenomena of time-dependent deformation of a slope on the left bank of Yalong River are described in detail. They reveal that the slope has experienced a long-term deformation and its mechanism can be considered as a slIp along the weak bed plane and buckling on the foot of the slope. Further evidence indicates that the deformation of the slope is quite light, since the slope is under a stable condition at present.
A lot of facts from field investigations show that a time-dependent deformation of a high rock slope could occur before its instability. Accompanied with this process, a potential slIp surface develops gradually in the slope, and finally cut through due to progressive failure along it or some triggering factors. In this paper, the phenomena of time-dependent deformation of a slope on the left bank of Yalong River are described in detail. They reveal that the slope has experienced a long-term deformation and its mechanism can be considered as a slIp along the weak bed plane and buckling on the foot of the slope. Further evidence indicates that the deformation of the slope is quite light, since the slope is under a stable condition at present.
2000, 8(2): 154-159.
Based on the experimental behaviours of rock blocks when sliding in the paper, the mechanism of rock interface friction resistance is analysed. At last, a model is proposed to describe time effect of the rock interface friction resistance when viscous sliding and displacement softening occur,the relaxation model of friction resistance.
Based on the experimental behaviours of rock blocks when sliding in the paper, the mechanism of rock interface friction resistance is analysed. At last, a model is proposed to describe time effect of the rock interface friction resistance when viscous sliding and displacement softening occur,the relaxation model of friction resistance.
2000, 8(2): 160-163.
A cusp catastrophic model of water-inrush from coal floor is established and a mechanism for water inrush due to the floor instability and destruction is analysed in the paper. The ratio of water pressure and stress, I p, can be derived from the model. When I p1,water-inrush from the floor can be caused. When I p1, water-inrush from coal floor can not be caused. The critical depth of the mining water-conducting fissure zone, h 1l, for water inrush from coal floor can be derived from the bifurcation curve equation. When h 1h 1l, water inrush from coal floor can be caused. When h 1h 1l, water-inrush from coal floor can not be caused.
A cusp catastrophic model of water-inrush from coal floor is established and a mechanism for water inrush due to the floor instability and destruction is analysed in the paper. The ratio of water pressure and stress, I p, can be derived from the model. When I p1,water-inrush from the floor can be caused. When I p1, water-inrush from coal floor can not be caused. The critical depth of the mining water-conducting fissure zone, h 1l, for water inrush from coal floor can be derived from the bifurcation curve equation. When h 1h 1l, water inrush from coal floor can be caused. When h 1h 1l, water-inrush from coal floor can not be caused.
2000, 8(2): 164-168.
The acoustic emission (AE) behavior in the process of rock fracture is not only closely related to the rock types but also to the load and microfracture progress. Thus, AE wave spectrum obtained from loaded rock specimen contains a great amount of information concerning microfracture of rock.The microfracture mechanism of rock under compressive-shear loading is studied using wave-spectrum analysis in this paper. the relation between wave-specturm behavior at different loading stages and mechanical response of rock and critical crack propagation is discussed. The results show that wave-spectrum parameters are more sensitive to microfracture of rock than to load itself, which is quite significant for solving engineering problems, such as safty estimation and rock burst prediction in mining process and slope stability analysis in geological engineering.
The acoustic emission (AE) behavior in the process of rock fracture is not only closely related to the rock types but also to the load and microfracture progress. Thus, AE wave spectrum obtained from loaded rock specimen contains a great amount of information concerning microfracture of rock.The microfracture mechanism of rock under compressive-shear loading is studied using wave-spectrum analysis in this paper. the relation between wave-specturm behavior at different loading stages and mechanical response of rock and critical crack propagation is discussed. The results show that wave-spectrum parameters are more sensitive to microfracture of rock than to load itself, which is quite significant for solving engineering problems, such as safty estimation and rock burst prediction in mining process and slope stability analysis in geological engineering.
2000, 8(2): 169-174.
Due to the random distribution of geotechnical data and the sliding surface, it is more significant to evaluate slope stability and to design a slope by random searching technique and failure probability method. In the paper, the lowest position of the most dangerous sliding surface and its dIp angle, as well as the load combination reflecting the maximum failure probability of the entrance high slope of Xiaolangdi Reservoir, Yellow River, China, are given by random searching technique and probability method. At the end of the paper, the author points out that design of a step slope with 1:0.2 gradient has an advantage over that of the vertical one. The results could also be provided as a scientific basis for determination of depth and width of slope reinforcement .
Due to the random distribution of geotechnical data and the sliding surface, it is more significant to evaluate slope stability and to design a slope by random searching technique and failure probability method. In the paper, the lowest position of the most dangerous sliding surface and its dIp angle, as well as the load combination reflecting the maximum failure probability of the entrance high slope of Xiaolangdi Reservoir, Yellow River, China, are given by random searching technique and probability method. At the end of the paper, the author points out that design of a step slope with 1:0.2 gradient has an advantage over that of the vertical one. The results could also be provided as a scientific basis for determination of depth and width of slope reinforcement .
2000, 8(2): 175-179.
Based on the analysis of method for establishing elastic and plastic damage evolution equation based on triaxial tests. The validity of the method is verified. Accordingly, an elastic and plastic equation is proposed for two classes of rock mass in Xiaoguanzhuang Iron Mine of the LuZhong Metallurgy Cooperation. With few parameters and clear physical concept, the equation is of great significance in numerical analysis of the tunnel in these rocks.
Based on the analysis of method for establishing elastic and plastic damage evolution equation based on triaxial tests. The validity of the method is verified. Accordingly, an elastic and plastic equation is proposed for two classes of rock mass in Xiaoguanzhuang Iron Mine of the LuZhong Metallurgy Cooperation. With few parameters and clear physical concept, the equation is of great significance in numerical analysis of the tunnel in these rocks.
2000, 8(2): 180-185.
The author has analyzed the characteristics of hydrogeological conditions and their influence on water inrush preventing and treatment in Chambeshi Copper Mine, Zambia, Suggests a drainage scheme for the main orebody and ununiformly arranged the drainage works in space, mainly at the mining level, which is different from customary way in the local mines. In order to successful realizing the scheme, some measures should be taken in the early time of mine reopening.
The author has analyzed the characteristics of hydrogeological conditions and their influence on water inrush preventing and treatment in Chambeshi Copper Mine, Zambia, Suggests a drainage scheme for the main orebody and ununiformly arranged the drainage works in space, mainly at the mining level, which is different from customary way in the local mines. In order to successful realizing the scheme, some measures should be taken in the early time of mine reopening.
2000, 8(2): 186-190.
In a case study of Baota landslide in the reservoir area of Three-Gorges project, a conceptual model for ground water systems in large-scale landslide was established by integrating the studies of groundwater dynamic field, physical-chemical characteristics, environmental isotopes, and temperature of ground water in the landslide. This model includes recharge, seepage, discharge conditions of ground water varying with the environmental factors (e.g. rainfall, reservoir impounding, and artificial surface water recharge, etc.). This is one of the keys to predict the slope stability and to take countermeasures to controlling landslide.
In a case study of Baota landslide in the reservoir area of Three-Gorges project, a conceptual model for ground water systems in large-scale landslide was established by integrating the studies of groundwater dynamic field, physical-chemical characteristics, environmental isotopes, and temperature of ground water in the landslide. This model includes recharge, seepage, discharge conditions of ground water varying with the environmental factors (e.g. rainfall, reservoir impounding, and artificial surface water recharge, etc.). This is one of the keys to predict the slope stability and to take countermeasures to controlling landslide.
2000, 8(2): 191-196.
A large Shuibuya hydropower plant will be constructed on the very complicated geological condition. There is a challenge appearing in design and construction of the project. Considering the results of detailed geological exploration, a quality assessment of rock mass for underground buildings of the hydropower plant is carried out. The authors describe the engineering rock mass quality for underground opening as follow: Q und-r=90+3 *R c+250 *K v-100(K 1 +K 2+K 3). The result of RMR for quality assessment of rock mass for underground building of Shuibuya hydropower plant project are illustrated. At last the progressive feedback design and informative construction related to the underground working is presented.
A large Shuibuya hydropower plant will be constructed on the very complicated geological condition. There is a challenge appearing in design and construction of the project. Considering the results of detailed geological exploration, a quality assessment of rock mass for underground buildings of the hydropower plant is carried out. The authors describe the engineering rock mass quality for underground opening as follow: Q und-r=90+3 *R c+250 *K v-100(K 1 +K 2+K 3). The result of RMR for quality assessment of rock mass for underground building of Shuibuya hydropower plant project are illustrated. At last the progressive feedback design and informative construction related to the underground working is presented.
2000, 8(2): 197-201.
From the engineering-geological aspect, this article analyzes the deformation of surface soil under special geological conditions caused by mining activities, and both vertical frictional force and toppling force, which are caused by this deformation, may lead to shaft failure are also studied. At the end of this article it is concluded that the engineering-geological problems and corresponding prevention measures from the shaft failure should deserve special attention.
From the engineering-geological aspect, this article analyzes the deformation of surface soil under special geological conditions caused by mining activities, and both vertical frictional force and toppling force, which are caused by this deformation, may lead to shaft failure are also studied. At the end of this article it is concluded that the engineering-geological problems and corresponding prevention measures from the shaft failure should deserve special attention.
2000, 8(2): 202-205.
In this paper, geological environment and geomorphological characteristics of geological hazards on Banyanshan mountain are introduced, and formation mechanism of the hazards is discussed. It is concluded that any large geological hazard will not occur, since the dangerous rock is in the late ereep stage and deformation tends to be stable. Therefore, the most important job is to control the landslide stability.
In this paper, geological environment and geomorphological characteristics of geological hazards on Banyanshan mountain are introduced, and formation mechanism of the hazards is discussed. It is concluded that any large geological hazard will not occur, since the dangerous rock is in the late ereep stage and deformation tends to be stable. Therefore, the most important job is to control the landslide stability.
2000, 8(2): 206-212.
Study of the regional stability and preliminary siting of the Anqing bridge are the important, basic work prior to the construction of the bridge. According to the requirements of the preliminary feasibility research, a study of remote sensing application aims to do the following works: (1) analysis of the alternative areas of the preliminary bridge site and the characteristics of its surrounding geological structures, understanding distribution of old and young faults in the area and analysis of their activity and evaluation ofthe regional stability by means of geological interpretation of the aerial and Landsat images; (2) analysis of evolution of the Changjiang River banks in the possible bridge site area and evaluation of its stability by using the aerial and Landsat images taken from 1950s to 1990s; and (3) analysis of engineering geological conditions of the preliminarily sited bridge areas, and put forward an optimum scheme.
Study of the regional stability and preliminary siting of the Anqing bridge are the important, basic work prior to the construction of the bridge. According to the requirements of the preliminary feasibility research, a study of remote sensing application aims to do the following works: (1) analysis of the alternative areas of the preliminary bridge site and the characteristics of its surrounding geological structures, understanding distribution of old and young faults in the area and analysis of their activity and evaluation ofthe regional stability by means of geological interpretation of the aerial and Landsat images; (2) analysis of evolution of the Changjiang River banks in the possible bridge site area and evaluation of its stability by using the aerial and Landsat images taken from 1950s to 1990s; and (3) analysis of engineering geological conditions of the preliminarily sited bridge areas, and put forward an optimum scheme.
2000, 8(2): 213-217.
The functional construction, development tendency, and several key techhnical problems of software system for Automatic Monitoring on geological engineering are discussed in this paper. Studied these key problems and the characteristics ofdeformation and failure of geological engineering works, the authors developed a software system for automatic monitoring on large hydropower station slope works. Its powerful functions, special features and data analyzing, and prediction subsystem are introduced.
The functional construction, development tendency, and several key techhnical problems of software system for Automatic Monitoring on geological engineering are discussed in this paper. Studied these key problems and the characteristics ofdeformation and failure of geological engineering works, the authors developed a software system for automatic monitoring on large hydropower station slope works. Its powerful functions, special features and data analyzing, and prediction subsystem are introduced.
2000, 8(2): 218-223.
To understand characteristics of slope deformation of an open pit is very important for its stability evaluation, mining and slope deformation monitoring. However, it is difficult to predict due to the complicated mining conditions. In this paper, FLAC method is used to spatiotemporally analyze the characteristics of deformation of a stable slope and an unstable slope of an open pit, and the effects of excavated zones and multi-stage cutting on the slope deformation. The result indicates that FLAC is an effective method for analyzing the deformation of a slope either stable or unstble, and that excavated zones and mining velocity have some effects on the deformation.
To understand characteristics of slope deformation of an open pit is very important for its stability evaluation, mining and slope deformation monitoring. However, it is difficult to predict due to the complicated mining conditions. In this paper, FLAC method is used to spatiotemporally analyze the characteristics of deformation of a stable slope and an unstable slope of an open pit, and the effects of excavated zones and multi-stage cutting on the slope deformation. The result indicates that FLAC is an effective method for analyzing the deformation of a slope either stable or unstble, and that excavated zones and mining velocity have some effects on the deformation.
2000, 8(2): 224-228.
There often exist several kinds of split planes in a slope. Could these planes delevop into sliding surface, it depends on several factors, for example, stress state, properties, shape and development density of the split planes, and so on. Through analysing these slide planes, stress,state, and cluster analysis, we determine several groups of the latent slide planes, then we classify and analyse these groups of split planes in slope. The primary method is that each sample of each group (split planes or latent slide planes) is regarded as one kind. According to distance or similar coefficient between the samples, we merge two kinds, which are more similar, into one kind, and calculate the distance of new kind to other kinds, and so on, finally, merge into a kind which we need, and determine one kind of split plane which may possibly develope into active sliding surface.
There often exist several kinds of split planes in a slope. Could these planes delevop into sliding surface, it depends on several factors, for example, stress state, properties, shape and development density of the split planes, and so on. Through analysing these slide planes, stress,state, and cluster analysis, we determine several groups of the latent slide planes, then we classify and analyse these groups of split planes in slope. The primary method is that each sample of each group (split planes or latent slide planes) is regarded as one kind. According to distance or similar coefficient between the samples, we merge two kinds, which are more similar, into one kind, and calculate the distance of new kind to other kinds, and so on, finally, merge into a kind which we need, and determine one kind of split plane which may possibly develope into active sliding surface.
2000, 8(2): 229-234.
The calculation in design of mixed support with multi-layer supporting points for deep foundation pit in multi-layer soil affected by the surface loading and ground water is very complex. The authors solved the calculation problem in design of mixed support through finding the commonly used algorithm for the calculation in design of foundation pit, which has arbitrary number of soil layers and arbitrary number of support points, and programmed with a commonly used software. The authors used an object-oriented programming method to design interfaces which is of Windows style, it improved the applicability of software.
The calculation in design of mixed support with multi-layer supporting points for deep foundation pit in multi-layer soil affected by the surface loading and ground water is very complex. The authors solved the calculation problem in design of mixed support through finding the commonly used algorithm for the calculation in design of foundation pit, which has arbitrary number of soil layers and arbitrary number of support points, and programmed with a commonly used software. The authors used an object-oriented programming method to design interfaces which is of Windows style, it improved the applicability of software.
2000, 8(2): 235-238.
Earthquake resistance and protection decision making involves a lot of fuzzy information that is very important to the whole analysis. In this paper a methodology to incorporate the fuzzy information into a probabilistic approach to seismic risk analysis and the decision making is proposed, a princIple to model the fuzzy information by fuzzy set is introduced, and a vertex method for interval analysis to further process the fuzzy information is discussed. As an example, these methods, along with occurrence probability model of earthquake with different intensities based on the Poisson distribution, are used in analysis of seismic risk in Nanjing City. then a fuzzy conclusion is presented as a reference for decision making about earthquake resistance and protectionpolicy.
Earthquake resistance and protection decision making involves a lot of fuzzy information that is very important to the whole analysis. In this paper a methodology to incorporate the fuzzy information into a probabilistic approach to seismic risk analysis and the decision making is proposed, a princIple to model the fuzzy information by fuzzy set is introduced, and a vertex method for interval analysis to further process the fuzzy information is discussed. As an example, these methods, along with occurrence probability model of earthquake with different intensities based on the Poisson distribution, are used in analysis of seismic risk in Nanjing City. then a fuzzy conclusion is presented as a reference for decision making about earthquake resistance and protectionpolicy.
2000, 8(2): 239-243.
Shots and receivers are placed on the ground surface around the studied area ; the observation is performed by using conventional seismic method. The energy exited from sources arrives at receivers. The signals recorded are processed by tomographic inversion and a P-wawe velocity image is produced. The image shows velocity distributions in shallow layers and weathering deposits, as well as geological structure of bedrock. This technique was used in an engineering-geological survey. The velocity CT image obtained is coincident with geologic outcrops and excavation result.
Shots and receivers are placed on the ground surface around the studied area ; the observation is performed by using conventional seismic method. The energy exited from sources arrives at receivers. The signals recorded are processed by tomographic inversion and a P-wawe velocity image is produced. The image shows velocity distributions in shallow layers and weathering deposits, as well as geological structure of bedrock. This technique was used in an engineering-geological survey. The velocity CT image obtained is coincident with geologic outcrops and excavation result.
2000, 8(2): 244-248.
Slope is dynamic system affected by many factors and varies with time and in space. It is charactertized by limited data, instability, and without prototype, etc. Thus, use of the existing experience and knowledge is very important in slope stability analysis. A new approach to slope stability analysis and evaluation, using the existing knowledge, is presented in this paper based on the gray system and analogue. It has been shown from examples that the method provided here is simple and practical.
Slope is dynamic system affected by many factors and varies with time and in space. It is charactertized by limited data, instability, and without prototype, etc. Thus, use of the existing experience and knowledge is very important in slope stability analysis. A new approach to slope stability analysis and evaluation, using the existing knowledge, is presented in this paper based on the gray system and analogue. It has been shown from examples that the method provided here is simple and practical.
2000, 8(2): 249-252.
Based on the preferred plane theory for regional stability assessment, princIple and methods of artificial neural network (ANN), the model of back propagation (BP) neural network and its algorithm for the preferredfault recognition are discussed in this paper. Practical examples indicate that the new method using BP neural network to determine preferred fault is effective and the prediction result is good.
Based on the preferred plane theory for regional stability assessment, princIple and methods of artificial neural network (ANN), the model of back propagation (BP) neural network and its algorithm for the preferredfault recognition are discussed in this paper. Practical examples indicate that the new method using BP neural network to determine preferred fault is effective and the prediction result is good.
2000, 8(2): 253-256.
The elasto-plastic analyses of the stability of Outang old landslide after construction of Three-Gorges Reservoir are carried out by using 2D FEM. In the computation, the effect of water level variation, seepage flow pressure, construction load, and seismic force on the stability of landslide is considered, and the critical failure conditions of the landslide are given also.
The elasto-plastic analyses of the stability of Outang old landslide after construction of Three-Gorges Reservoir are carried out by using 2D FEM. In the computation, the effect of water level variation, seepage flow pressure, construction load, and seismic force on the stability of landslide is considered, and the critical failure conditions of the landslide are given also.
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