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Editor Work2004 Vol. 12, No. 3
Previous Issue
2004, 12(3): 225-231.
Abstract
Rock fall, a geological hazard, has not attracted attention of researchers for a long time. This paper first introduces some concepts followed with connotations, extensions and characteristics of rock falls. In fact, rock falls can occur during various dynamic geological phenomena. Both natural forces and human activities can cause rock falls, which may result in losses of human lives and properties and may affect the development of communities. Therefore, this paper focuses on the rockfall itself, which can help us not only to simplify the resolution of the problem, but also gain a deep insight into mechanisms of rock falls. The authors then recommend that rock falls be treated as one type of geological hazard, i.e. rock fall hazard. At the end, the authors also summarize current research focuses and fundamental issues related to rock falls in the world.
Rock fall, a geological hazard, has not attracted attention of researchers for a long time. This paper first introduces some concepts followed with connotations, extensions and characteristics of rock falls. In fact, rock falls can occur during various dynamic geological phenomena. Both natural forces and human activities can cause rock falls, which may result in losses of human lives and properties and may affect the development of communities. Therefore, this paper focuses on the rockfall itself, which can help us not only to simplify the resolution of the problem, but also gain a deep insight into mechanisms of rock falls. The authors then recommend that rock falls be treated as one type of geological hazard, i.e. rock fall hazard. At the end, the authors also summarize current research focuses and fundamental issues related to rock falls in the world.
2004, 12(3): 232-236.
Using the Monte Carlo method, the normal slope model of grid and bedded rock can be analyzed. On the random combination of steep and flat series of joints in the J- slope , failure probability and reliability index can be calculated under the action of water and earthquake. The high slope stability of one copper mine in Jiangxi China was used by the proposed method, and the result is satisfied.
Using the Monte Carlo method, the normal slope model of grid and bedded rock can be analyzed. On the random combination of steep and flat series of joints in the J- slope , failure probability and reliability index can be calculated under the action of water and earthquake. The high slope stability of one copper mine in Jiangxi China was used by the proposed method, and the result is satisfied.
2004, 12(3): 237-242.
Karstified rock is a special type of rock mass, in which so many solution caverns are developed under influence of some natural factors such as water flowing. In this paper, mathematic description and computer display of three-dimensional geological mass are provided as a carrier of the karstified rock. The determination of the shape and size of ellipsoid, the generation of composite cavern, the mathematic modeling of three-dimensional random caverns and the mathematic description and computer display of the deterministic cavern are then discussed in detail. Mathematic modeling for three-dimensional random caverns in karstified rock suggested in this paper provides visualizational means for assessment of solution ratio and permeability of karstified rock and can effectively guide computer display programming for three-dimensional random caverns.
Karstified rock is a special type of rock mass, in which so many solution caverns are developed under influence of some natural factors such as water flowing. In this paper, mathematic description and computer display of three-dimensional geological mass are provided as a carrier of the karstified rock. The determination of the shape and size of ellipsoid, the generation of composite cavern, the mathematic modeling of three-dimensional random caverns and the mathematic description and computer display of the deterministic cavern are then discussed in detail. Mathematic modeling for three-dimensional random caverns in karstified rock suggested in this paper provides visualizational means for assessment of solution ratio and permeability of karstified rock and can effectively guide computer display programming for three-dimensional random caverns.
2004, 12(3): 243-246.
Based on geological analyses, this paper presents criteria of bending and breaking in a countertendency slope by a simple stress analysis. In the analyses, a random rock stratum is simplified as a girder model under a complex loading. According to instantaneous disconnection between strata at failure, it is assumed that the downside of the upper stratum faces air. Taking into account the deadweight and add-ons loading (gravity of the upper stratum, friction stress of interface and so on), the stress criterion of bending and breaking can then be established based on the maximum tensile stress rule. From the stress criterion of bending and breaking, the flexibility criterion can be found. The stress and flexibility criteria can be used in assessment of the potential failure and design of control measures for prevention of bending and breaking in the countertendency layered slopes.
Based on geological analyses, this paper presents criteria of bending and breaking in a countertendency slope by a simple stress analysis. In the analyses, a random rock stratum is simplified as a girder model under a complex loading. According to instantaneous disconnection between strata at failure, it is assumed that the downside of the upper stratum faces air. Taking into account the deadweight and add-ons loading (gravity of the upper stratum, friction stress of interface and so on), the stress criterion of bending and breaking can then be established based on the maximum tensile stress rule. From the stress criterion of bending and breaking, the flexibility criterion can be found. The stress and flexibility criteria can be used in assessment of the potential failure and design of control measures for prevention of bending and breaking in the countertendency layered slopes.
2004, 12(3): 247-252.
The paper discussed the deformation mechanism of one high steep dipslope in Jinping hydropower station. Through field investigation, experimental analysis and numerical simulation, the authors have a more profound insight into the problem. The previous conclusions were discussed in the paper. There is evidence that problems exist in earlier analysis. As a result, a new insight was gained. The results indicate that the deformation of deep rock layer at Jiefanggou left bank high slope is caused by a combination of deep unloading relaxation at slope in the course of cutting valley in high terra stress area and bending-toppling of deep rock layer at high dipslope.
The paper discussed the deformation mechanism of one high steep dipslope in Jinping hydropower station. Through field investigation, experimental analysis and numerical simulation, the authors have a more profound insight into the problem. The previous conclusions were discussed in the paper. There is evidence that problems exist in earlier analysis. As a result, a new insight was gained. The results indicate that the deformation of deep rock layer at Jiefanggou left bank high slope is caused by a combination of deep unloading relaxation at slope in the course of cutting valley in high terra stress area and bending-toppling of deep rock layer at high dipslope.
2004, 12(3): 253-258.
Through analyzing the Maoba synclining karst cave exposed by the Yuanliangshan tunnel and the distinct distribution of karst in superficial layers, the authors identified characteristics of deep karst development and the contributing factors. The results indicated that the karst water moves downwards into the deep layers under favorable hydraulic gradients or pressure heads, especially under influence of water gravity. As a result, the karst is developed at depth with erosion of water. At the same time, a karst zone is developed between the thick confining bed and the base of the drainage. In the same geological formation, the similarity in distribution is observed for both shallow and deep layers.
Through analyzing the Maoba synclining karst cave exposed by the Yuanliangshan tunnel and the distinct distribution of karst in superficial layers, the authors identified characteristics of deep karst development and the contributing factors. The results indicated that the karst water moves downwards into the deep layers under favorable hydraulic gradients or pressure heads, especially under influence of water gravity. As a result, the karst is developed at depth with erosion of water. At the same time, a karst zone is developed between the thick confining bed and the base of the drainage. In the same geological formation, the similarity in distribution is observed for both shallow and deep layers.
2004, 12(3): 259-262.
In this paper the drillability of frozen clay is analyzed by using the elastic wave theory under an impact load. The main factors affecting the drillability of frozen soil are determined, namely temperature, wave velocity, impact inductility and chiseling specific work. The drillability tests of frozen clay are carried out under the seven different temperatures. The results show that it is appropriate to define drillability using the chiseling specific work factor because it has a good relationship with drill hole and can reflect the drillability of frozen clay quite well. The test results provide a good guideline for drilling in frozen soil.
In this paper the drillability of frozen clay is analyzed by using the elastic wave theory under an impact load. The main factors affecting the drillability of frozen soil are determined, namely temperature, wave velocity, impact inductility and chiseling specific work. The drillability tests of frozen clay are carried out under the seven different temperatures. The results show that it is appropriate to define drillability using the chiseling specific work factor because it has a good relationship with drill hole and can reflect the drillability of frozen clay quite well. The test results provide a good guideline for drilling in frozen soil.
2004, 12(3): 263-267.
By comparing geotechnical properties of sediments of the same ages, it has been found that there are a great difference between the soils from the north of Jiangsu and the Yangtse River delta. The authors then assess the deposition environment and the dynamic conditions and the origin of deposits in the two areas at the same ages. The results indicate that the physical and the mechanical properties of soil are closely related to the deposition environment and dynamic conditions and the origin of deposits. Therefore, understanding conditions of the soil deposition is a key to characterization of the soils geotechnical properties.
By comparing geotechnical properties of sediments of the same ages, it has been found that there are a great difference between the soils from the north of Jiangsu and the Yangtse River delta. The authors then assess the deposition environment and the dynamic conditions and the origin of deposits in the two areas at the same ages. The results indicate that the physical and the mechanical properties of soil are closely related to the deposition environment and dynamic conditions and the origin of deposits. Therefore, understanding conditions of the soil deposition is a key to characterization of the soils geotechnical properties.
2004, 12(3): 268-273.
Based on a comprehensive engineering geological investigation and supplemental explorations, a series of laboratory tests were conducted on the expansive soil and the improved soil along the Changde-Zhangjiajie Expressway. They included free swelling ratio, loaded swelling capacity, shrinkage, total swelling and shrinkage, distribution of granular particles, compressive strength, shear strength and California Bearing Ratio (CBR). Engineering properties of the expansive soil were then evaluated based on test results, which provided important guidelines for design and construction of pavement using the expansive soil as subsoil。
Based on a comprehensive engineering geological investigation and supplemental explorations, a series of laboratory tests were conducted on the expansive soil and the improved soil along the Changde-Zhangjiajie Expressway. They included free swelling ratio, loaded swelling capacity, shrinkage, total swelling and shrinkage, distribution of granular particles, compressive strength, shear strength and California Bearing Ratio (CBR). Engineering properties of the expansive soil were then evaluated based on test results, which provided important guidelines for design and construction of pavement using the expansive soil as subsoil。
2004, 12(3): 274-279.
The strength theories of geotechnical materials can be classified as single shear strength theory, tri-shear strength theory and twin-shear strength theory. They are represented by the Mohr-Coulomb theory, Drucker-Prager criterion and the twin-shear theory respectively. Each strength theory has its own representative element model. The strength theory is established by analyzing the stresses that cause the model element to fail and by developing the mathematical relationship among the stresses on the model. Based on the characteristics of failure and strength of rocks under symmetry compression tests and true tri-axial compression tests, the authors introduce a new twin-shear model and associated strength theories for rock materials.
The strength theories of geotechnical materials can be classified as single shear strength theory, tri-shear strength theory and twin-shear strength theory. They are represented by the Mohr-Coulomb theory, Drucker-Prager criterion and the twin-shear theory respectively. Each strength theory has its own representative element model. The strength theory is established by analyzing the stresses that cause the model element to fail and by developing the mathematical relationship among the stresses on the model. Based on the characteristics of failure and strength of rocks under symmetry compression tests and true tri-axial compression tests, the authors introduce a new twin-shear model and associated strength theories for rock materials.
2004, 12(3): 280-284.
Bands of clefts appeared on the top of the water-entrance hole at a southwestern hydropower station during the excavation attracted lots of attention. Based on in situ investigation, the authors characterized the failure mode and simulate the excavation process using the FLAC~(3D). The results of calculation indicate the displacement of the slope and verify the development of the bands of clefts. The model also predicted the distribution of displacements within the slope after reinforcement. The results indicate that the maximum displacement in X direction amounts up to 5.4cm. With the effective anchoring reinforcement the slope reaches its stability by adjusting the stress and strain.
Bands of clefts appeared on the top of the water-entrance hole at a southwestern hydropower station during the excavation attracted lots of attention. Based on in situ investigation, the authors characterized the failure mode and simulate the excavation process using the FLAC~(3D). The results of calculation indicate the displacement of the slope and verify the development of the bands of clefts. The model also predicted the distribution of displacements within the slope after reinforcement. The results indicate that the maximum displacement in X direction amounts up to 5.4cm. With the effective anchoring reinforcement the slope reaches its stability by adjusting the stress and strain.
2004, 12(3): 285-291.
Based on 4 basic hypotheses, a generic Rankine theory is established and verified by idealized experiments. Its application in the foundation pit project in the Dongzhimen Station of the Beijing subway line No.13 also proves its effectiveness by predicting earth pressure which is very close to results obtained from field measurements. The generic Rankine theory establishes the relationship of the soil experimental indexes with its in situ ones, which allows the estimate of in situ active or passive earth pressure with experimental indexes. For the unsaturated soil, this method provides a very accurate estimate of earth pressure from the direct shear experimental indexes, which overcomes the shortage of the extended Rankine theory. The formula can appropriately utilize existing engineering experience and data, which is a new way to application of the soils mechanics for unsaturated soils in engineering.
Based on 4 basic hypotheses, a generic Rankine theory is established and verified by idealized experiments. Its application in the foundation pit project in the Dongzhimen Station of the Beijing subway line No.13 also proves its effectiveness by predicting earth pressure which is very close to results obtained from field measurements. The generic Rankine theory establishes the relationship of the soil experimental indexes with its in situ ones, which allows the estimate of in situ active or passive earth pressure with experimental indexes. For the unsaturated soil, this method provides a very accurate estimate of earth pressure from the direct shear experimental indexes, which overcomes the shortage of the extended Rankine theory. The formula can appropriately utilize existing engineering experience and data, which is a new way to application of the soils mechanics for unsaturated soils in engineering.
2004, 12(3): 292-297.
Based on the experimental results of the temperature and deformation of reinforcement embankment and station roadbed in some tests of the Qinghai-Tibet railway, the authors analyze the characters of ground temperature and deformation in reinforcement embankment and station roadbed. The influence of different roadbed engineering construction on the roadbed crack due to embankment reinforcing and roadbed widening is then characterized.
Based on the experimental results of the temperature and deformation of reinforcement embankment and station roadbed in some tests of the Qinghai-Tibet railway, the authors analyze the characters of ground temperature and deformation in reinforcement embankment and station roadbed. The influence of different roadbed engineering construction on the roadbed crack due to embankment reinforcing and roadbed widening is then characterized.
2004, 12(3): 298-302.
The environment will be influenced when underground space is used and developed. This paper analyzes impacts which the subway construction will make on the surrounding environment on the basis of combining the engineering geology and hydrogeology of Nanjing and construction procedures of the subway. At the end of paper, the authors provide some measures for reducing such impacts.
The environment will be influenced when underground space is used and developed. This paper analyzes impacts which the subway construction will make on the surrounding environment on the basis of combining the engineering geology and hydrogeology of Nanjing and construction procedures of the subway. At the end of paper, the authors provide some measures for reducing such impacts.
2004, 12(3): 303-306.
Landslide-dams and associated lakes occur in many places around the world, which create natural reservoirs with their occurrence. However, they can cause great damages as floods break them or cause excessive overflow. Historically, some of them have broken quickly, while others could exist for a long time, and can create beautiful landscapes and/or hot spots for tourists around them. They can also help in the development of sustainable water resources. Landslide dams can be classified as three types: landslide dams, rock fall dams and debris flow dams based on their genesis. Because the life of a landslide-dam is determined by its genesis, it is very important to understand its genetic mechanism in their utilization. The paper analyzed the genesis of a landslide-dam, which was formed by slides from both its left and right banks. Because such a dam has been reported rarely, the results presented in this paper will provide a good guideline for future investigation of similar projects.
Landslide-dams and associated lakes occur in many places around the world, which create natural reservoirs with their occurrence. However, they can cause great damages as floods break them or cause excessive overflow. Historically, some of them have broken quickly, while others could exist for a long time, and can create beautiful landscapes and/or hot spots for tourists around them. They can also help in the development of sustainable water resources. Landslide dams can be classified as three types: landslide dams, rock fall dams and debris flow dams based on their genesis. Because the life of a landslide-dam is determined by its genesis, it is very important to understand its genetic mechanism in their utilization. The paper analyzed the genesis of a landslide-dam, which was formed by slides from both its left and right banks. Because such a dam has been reported rarely, the results presented in this paper will provide a good guideline for future investigation of similar projects.
2004, 12(3): 307-311.
Taking the clay buried nearly 430-600 meters deep in Juye mine area of Shandong province as an example, the authors analyze the general physical and mechanical parameters of soil. Considering the in-situ stress level of the deep soil at such a depth and its unloading change during the excavation proceeding of the vertical shaft building in the coal mine area, a triaxial servo controlled system is used to carry out the triaxial high pressure unloading tests. The axial stress is kept constant while gradually unloading the confining pressure from 11 MPa, 12 MPa and 14 MPa isotropic stress state is proceeded. The deformation and strength of the deep clay under triaxial high pressure unloading test are then analyzed to obtain related mechanical parameters. The results enriches the studying of soil mechanical properties under high pressure unloading conditions, and provides the basic engineering geological parameters for the building of the vertical shafts in Juye coal mine area.
Taking the clay buried nearly 430-600 meters deep in Juye mine area of Shandong province as an example, the authors analyze the general physical and mechanical parameters of soil. Considering the in-situ stress level of the deep soil at such a depth and its unloading change during the excavation proceeding of the vertical shaft building in the coal mine area, a triaxial servo controlled system is used to carry out the triaxial high pressure unloading tests. The axial stress is kept constant while gradually unloading the confining pressure from 11 MPa, 12 MPa and 14 MPa isotropic stress state is proceeded. The deformation and strength of the deep clay under triaxial high pressure unloading test are then analyzed to obtain related mechanical parameters. The results enriches the studying of soil mechanical properties under high pressure unloading conditions, and provides the basic engineering geological parameters for the building of the vertical shafts in Juye coal mine area.
2004, 12(3): 312-317.
Based on the indoor rainfall modeling experiment and stability analysis, the paper presents the deformation features and failure modes of municipal solid waste slope under rainfall conditions. By analyzing the displacement law of each part of slope, the process of deformation is divided into five phases. It is concluded that three types of failure occur, namely slip, slope surface scouring and landslide. At the end prevention measures are suggested.
Based on the indoor rainfall modeling experiment and stability analysis, the paper presents the deformation features and failure modes of municipal solid waste slope under rainfall conditions. By analyzing the displacement law of each part of slope, the process of deformation is divided into five phases. It is concluded that three types of failure occur, namely slip, slope surface scouring and landslide. At the end prevention measures are suggested.
2004, 12(3): 318-322.
The Polymer solidified material is prone to aging, especially in a desert environment where strong heat and ray radiations as well as oxidation may speed up the process of aging. This paper presents preliminary results of resistances to aging of SH, a new Polymer solidified material, by using an aging test of the SH-fixated sands. The results indicated that the resistance to aging of SH is better than other sand-fixing agents under periodic or continuous ultraviolet radiation. Therefore SH can be adopted in the fixation of sands in a desert environment.
The Polymer solidified material is prone to aging, especially in a desert environment where strong heat and ray radiations as well as oxidation may speed up the process of aging. This paper presents preliminary results of resistances to aging of SH, a new Polymer solidified material, by using an aging test of the SH-fixated sands. The results indicated that the resistance to aging of SH is better than other sand-fixing agents under periodic or continuous ultraviolet radiation. Therefore SH can be adopted in the fixation of sands in a desert environment.
2004, 12(3): 323-327.
The monitoring results of the forces applied on a soil-nailing support structure in a high slope project with weak rock and relative displacements are presented in this paper. The analysis of the monitoring data reveals that the working principle of soil-nailing support is different from not only an anchor structure, but also a soil-nailing wall. According to the monitoring results of the horizontal displacement in the slope during the project construction, the supporting parameters, cutting depth and supporting time for the slope were adjusted so that the high slope was kept stable on the whole.
The monitoring results of the forces applied on a soil-nailing support structure in a high slope project with weak rock and relative displacements are presented in this paper. The analysis of the monitoring data reveals that the working principle of soil-nailing support is different from not only an anchor structure, but also a soil-nailing wall. According to the monitoring results of the horizontal displacement in the slope during the project construction, the supporting parameters, cutting depth and supporting time for the slope were adjusted so that the high slope was kept stable on the whole.
2004, 12(3): 328-335.
Using the object-oriented software, PowerBuilder, and DLL theory, an object-oriented back analysis method was studied, which defined the relationship of object classes, established a message flow of the finite element and made a program of friendly interface and efficient operation. With the applications of the probability theory and the mathematical statistics principle, the objects function of the geomechanical engineering random back analysis was established based on the AIC criterion of the decision information theory and the maximum entropy criterion, and an expanded Bayes method was thus proposed to overcome shortcoming of the conventional Bayes method. The models and analytical methods presented in this paper were verified by some numerical examples.
Using the object-oriented software, PowerBuilder, and DLL theory, an object-oriented back analysis method was studied, which defined the relationship of object classes, established a message flow of the finite element and made a program of friendly interface and efficient operation. With the applications of the probability theory and the mathematical statistics principle, the objects function of the geomechanical engineering random back analysis was established based on the AIC criterion of the decision information theory and the maximum entropy criterion, and an expanded Bayes method was thus proposed to overcome shortcoming of the conventional Bayes method. The models and analytical methods presented in this paper were verified by some numerical examples.
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