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Editor Work2005 Vol. 13, No. 2
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2005, 13(2): 145-154.
Abstract
A large number of human-cutting slopes have been created since the city、town and road re-constructed at the Three Gorges Reservoir. According to statistic data, the high slopes are more than 3000, and 90% is unstable that severely threats the relocation. It is great difference with other place of China, the slopes have to be the site for the relocation at the reservoir. The stability-based slope utilization is considered, and the houses can be constructed at the upper, bottom, and even in the middle part of the slope. Meantime, the landscape sense should be protected since tourism. The paper summary the slope patterns, and analyzes the deformation and failure mechanics. Cases-study on slope stabilized and utilized is presented.
A large number of human-cutting slopes have been created since the city、town and road re-constructed at the Three Gorges Reservoir. According to statistic data, the high slopes are more than 3000, and 90% is unstable that severely threats the relocation. It is great difference with other place of China, the slopes have to be the site for the relocation at the reservoir. The stability-based slope utilization is considered, and the houses can be constructed at the upper, bottom, and even in the middle part of the slope. Meantime, the landscape sense should be protected since tourism. The paper summary the slope patterns, and analyzes the deformation and failure mechanics. Cases-study on slope stabilized and utilized is presented.
2005, 13(2): 155-159.
The relaxation and engineering characteristic of rock mass after slope excavation are studied based on the monitoring data from the slope excavation in a hydropower station. The results indicate that rock mass of the slope will be relaxed along the slope face after sideslope excavation and that the thickness of relaxation zone can be measured by engineering investigation, survey of seismic wave velocity and sound wave. The mechanical strength of rock mass will decreases after relaxation. Shoring immediately after excavation is one of the effective methods of preventing rock mass from relaxation.
The relaxation and engineering characteristic of rock mass after slope excavation are studied based on the monitoring data from the slope excavation in a hydropower station. The results indicate that rock mass of the slope will be relaxed along the slope face after sideslope excavation and that the thickness of relaxation zone can be measured by engineering investigation, survey of seismic wave velocity and sound wave. The mechanical strength of rock mass will decreases after relaxation. Shoring immediately after excavation is one of the effective methods of preventing rock mass from relaxation.
2005, 13(2): 160-163.
With underground measurements and similar material analogy modeling, the authors analyzed distribution of induced stresses in roof and floor of the seam, and the state of hydraulic supports and the single spile. The results show that supports have different sustaining states at different locations, of which the biggest abutment stress is located at the middle part of working face. For the same support, the abutment stress of the front columniation is larger than that of back one. The stress in surrounding rock of the ventilation entry is bigger than that of conveyor entry with a peak value of stress at a distance of 3 to 11 meters from the working face. The mining-induced stress in the same roof strata varies with the distance from the working face, and it also varies from one stratum to another. The larger the stress is, the closer the stratum is located to the coal seam. The largest stress is observed at a distance of 6 meters from the working face, while zero stress is at the working face. This study provides guidelines for design and management of the longwall top-coal caving, entry support and roof control.
With underground measurements and similar material analogy modeling, the authors analyzed distribution of induced stresses in roof and floor of the seam, and the state of hydraulic supports and the single spile. The results show that supports have different sustaining states at different locations, of which the biggest abutment stress is located at the middle part of working face. For the same support, the abutment stress of the front columniation is larger than that of back one. The stress in surrounding rock of the ventilation entry is bigger than that of conveyor entry with a peak value of stress at a distance of 3 to 11 meters from the working face. The mining-induced stress in the same roof strata varies with the distance from the working face, and it also varies from one stratum to another. The larger the stress is, the closer the stratum is located to the coal seam. The largest stress is observed at a distance of 6 meters from the working face, while zero stress is at the working face. This study provides guidelines for design and management of the longwall top-coal caving, entry support and roof control.
2005, 13(2): 164-168.
Mining subsidence is an important environmental geotechnical engineering problem in regional planning and transportation construction in Xuzhou. Engineering geological characteristics in east, west and north of Xuzhou are studied. The types of road hazards and their characteristics are also analyzed. Accordingly, the controlling measures are recommended.
Mining subsidence is an important environmental geotechnical engineering problem in regional planning and transportation construction in Xuzhou. Engineering geological characteristics in east, west and north of Xuzhou are studied. The types of road hazards and their characteristics are also analyzed. Accordingly, the controlling measures are recommended.
2005, 13(2): 169-173.
During the construction of Nanjing-Xian railway, engineering geological investigations revealed that tectonic fractures were developed in Neozoic lacustrine clays, off-loading fractures formed in Medie-Pleistocene alluvial or diluvial clays, whereas shrinking fractures occurred in Holoence alluvial or lacustrine clays. These fractures control types of slope failures, their scales and characteristics along the railroad trench. Special engineering measures were recommended and adopted to deal with slope engineering problems, and are proved effective in reducing such geological hazards.
During the construction of Nanjing-Xian railway, engineering geological investigations revealed that tectonic fractures were developed in Neozoic lacustrine clays, off-loading fractures formed in Medie-Pleistocene alluvial or diluvial clays, whereas shrinking fractures occurred in Holoence alluvial or lacustrine clays. These fractures control types of slope failures, their scales and characteristics along the railroad trench. Special engineering measures were recommended and adopted to deal with slope engineering problems, and are proved effective in reducing such geological hazards.
2005, 13(2): 174-178.
This paper introduces a concept of the approximately horizontal terrain based on Songjiapo landslide along the Guangnan expressway. The authors analyze the slip mechanism and recommend stopping method on the landslide of the approximately horizontal slope in red beds. The concept and method presented in this paper provide a good example and guidelines for investigation, design and construction of other similar work.
This paper introduces a concept of the approximately horizontal terrain based on Songjiapo landslide along the Guangnan expressway. The authors analyze the slip mechanism and recommend stopping method on the landslide of the approximately horizontal slope in red beds. The concept and method presented in this paper provide a good example and guidelines for investigation, design and construction of other similar work.
2005, 13(2): 179-182.
Due to plunderous mining and delay of environmental protection, serious deterioration of environment has occurred in China. Based on investigation of anthropogenic debris flow disasters in mines, the authors recommend a mitigation countermeasure, which includes two aspects: one is to strengthen management policy and the other is to implement concrete engineering measures.
Due to plunderous mining and delay of environmental protection, serious deterioration of environment has occurred in China. Based on investigation of anthropogenic debris flow disasters in mines, the authors recommend a mitigation countermeasure, which includes two aspects: one is to strengthen management policy and the other is to implement concrete engineering measures.
2005, 13(2): 183-188.
Corrosion building foundations caused by groundwater is a type of natural hazard developed widely and slowly. It poses the greatest threat to the foundations of towns in the red beds area. Taking the City of Tianshui, located on red beds, as an example, the author studied the causes of generation of corrosive groundwater based on long-term historical chemical analysis of groundwater data. The countermeasures of preventing building foundation from corrosion by groundwater are recommended at the end of the paper.
Corrosion building foundations caused by groundwater is a type of natural hazard developed widely and slowly. It poses the greatest threat to the foundations of towns in the red beds area. Taking the City of Tianshui, located on red beds, as an example, the author studied the causes of generation of corrosive groundwater based on long-term historical chemical analysis of groundwater data. The countermeasures of preventing building foundation from corrosion by groundwater are recommended at the end of the paper.
2005, 13(2): 189-194.
By means of petrographic microscopic observation, X-ray diffraction(XRD) qualitative and quantitative analysis,scanning electron microscopy(SEM) as well as differential thermal analysis(DTA),this paper describes the cementation characteristics of sandstone at Longyou Grottoes in Zhejiang province which will provide scientific basis for our study on weathering process and preservation measures of the project mentioned above.
By means of petrographic microscopic observation, X-ray diffraction(XRD) qualitative and quantitative analysis,scanning electron microscopy(SEM) as well as differential thermal analysis(DTA),this paper describes the cementation characteristics of sandstone at Longyou Grottoes in Zhejiang province which will provide scientific basis for our study on weathering process and preservation measures of the project mentioned above.
2005, 13(2): 195-199.
Based on the feature of the existing railway,the authors analyze types and mechanisms of roadbed defects. The authors then present a new method in detection of roadbed defects, which combines the spot detection and section verification using modern equipment. Considering complexity of measures for treatment of roadbed defection as well as difficulties in their implementation, the authors conclude that an intelligent management system of railway roadbed defects will be a very effective tool in assessing railroad roadbed defects and selecting appropriate measures for treatment.
Based on the feature of the existing railway,the authors analyze types and mechanisms of roadbed defects. The authors then present a new method in detection of roadbed defects, which combines the spot detection and section verification using modern equipment. Considering complexity of measures for treatment of roadbed defection as well as difficulties in their implementation, the authors conclude that an intelligent management system of railway roadbed defects will be a very effective tool in assessing railroad roadbed defects and selecting appropriate measures for treatment.
2005, 13(2): 200-205.
Ancient landslides in the reservoir region are always of great concern. Therefore, it is important to assess the threats they pose to the safety of hydraulic projects, which should be accomplished by a comprehensive analysis instead of a simple mechanical calculation. Taking ancient landslide No. VIII in Xiabandi reservoir as an example, the authors analyze and predict compressively its stability after impoundment by employing multiple methods including identification by observed geological phenomenon, analysis of genetic mechanisms and inversion of motion features, engineering analogy, rigid body limiting equilibrium calculation, numerical simulation, etc. This comprehensive method can be used to develop guidelines for assuring the stability of reservoir landslides.
Ancient landslides in the reservoir region are always of great concern. Therefore, it is important to assess the threats they pose to the safety of hydraulic projects, which should be accomplished by a comprehensive analysis instead of a simple mechanical calculation. Taking ancient landslide No. VIII in Xiabandi reservoir as an example, the authors analyze and predict compressively its stability after impoundment by employing multiple methods including identification by observed geological phenomenon, analysis of genetic mechanisms and inversion of motion features, engineering analogy, rigid body limiting equilibrium calculation, numerical simulation, etc. This comprehensive method can be used to develop guidelines for assuring the stability of reservoir landslides.
2005, 13(2): 206-211.
In 1992, four local peasants found large-scale ancient man-made shallow rock caverns in Longyou, Zhejiang. This finding attracted the attention of many specialists from different fields: archeologists, engineering geologists and rock mechanics specialists among others. Since the opening of the site to the public in 1992 many damages have occurred including collapse of the roof and partition wall, shear or tension failures of pillars and weathering resulted from the frequent drying and wetting cycle. In order to protect such historic marvel, the authors evaluate engineering geological and hydrogeological conditions of 5 caverns to develop guidelines for design of protective measures.
In 1992, four local peasants found large-scale ancient man-made shallow rock caverns in Longyou, Zhejiang. This finding attracted the attention of many specialists from different fields: archeologists, engineering geologists and rock mechanics specialists among others. Since the opening of the site to the public in 1992 many damages have occurred including collapse of the roof and partition wall, shear or tension failures of pillars and weathering resulted from the frequent drying and wetting cycle. In order to protect such historic marvel, the authors evaluate engineering geological and hydrogeological conditions of 5 caverns to develop guidelines for design of protective measures.
2005, 13(2): 212-217.
This paper presents a case study of stability analysis in a huge underground powerhouse. Solid models of caverns with fractures are created using AutoCAD2002/2004 software with programmed modules for excavations/cutting, which specify arch crown, upstream side wall and downstream side wall as cross sectional planes. Based on these fractures, 21 blocks are chosen as deterministic blocks and their stabilities are then assessed. At last, assessment results are given for all deterministic blocks including following attributes: fractures jointed methods, sliding methods, area, depth, volume, safety factor, and location in caverns.
This paper presents a case study of stability analysis in a huge underground powerhouse. Solid models of caverns with fractures are created using AutoCAD2002/2004 software with programmed modules for excavations/cutting, which specify arch crown, upstream side wall and downstream side wall as cross sectional planes. Based on these fractures, 21 blocks are chosen as deterministic blocks and their stabilities are then assessed. At last, assessment results are given for all deterministic blocks including following attributes: fractures jointed methods, sliding methods, area, depth, volume, safety factor, and location in caverns.
2005, 13(2): 218-221.
Based on analysis of the force field in an inclined bedding slope, the authors present a mechanical model, in which the slope is treated as a cantilever beam on the elastic foundation. The internal stresses of the beam are calculated under the action of different forces using the elastic theory. The safety coefficient of the beam is then determined according to Mohr-Coulomb criterion. As a result, a critical length of the stable slope is obtained. By comparing results in this paper with the results obtained from the catastrophic theory method, the authors conclude that the method presented in this paper is applicable for such analysis.
Based on analysis of the force field in an inclined bedding slope, the authors present a mechanical model, in which the slope is treated as a cantilever beam on the elastic foundation. The internal stresses of the beam are calculated under the action of different forces using the elastic theory. The safety coefficient of the beam is then determined according to Mohr-Coulomb criterion. As a result, a critical length of the stable slope is obtained. By comparing results in this paper with the results obtained from the catastrophic theory method, the authors conclude that the method presented in this paper is applicable for such analysis.
2005, 13(2): 222-226.
This paper presents a case study for 3-D simulation of deformation characteristics of toppling rock slope using a slope simulation model at Longtan hydropower station as an example. Deformation of the toppling rock slope is simulated for different angles between the slope strike and the terrene strike. The deformation curves are then characterized qualitatively.
This paper presents a case study for 3-D simulation of deformation characteristics of toppling rock slope using a slope simulation model at Longtan hydropower station as an example. Deformation of the toppling rock slope is simulated for different angles between the slope strike and the terrene strike. The deformation curves are then characterized qualitatively.
2005, 13(2): 227-230.
This paper discusses the characteristics of different theoretical and computational methods for settlement assessment. The SPT method and transient R wave method are selected in this study. With comparison of theoretical calculations and the observed in-situ data, the authors conclude that these two methods are proved to be convenient and promising for further development.
This paper discusses the characteristics of different theoretical and computational methods for settlement assessment. The SPT method and transient R wave method are selected in this study. With comparison of theoretical calculations and the observed in-situ data, the authors conclude that these two methods are proved to be convenient and promising for further development.
2005, 13(2): 231-235.
Shaft-lining non-mining fracture is a kind of engineering geological hazard, which results from interaction between human engineering and natural environment and could cause great economic losses. The neural network and the fuzzy neural network methods are used for forecasting and judgment of shaft-lining fractures. The results show that neural network and fuzzy neural network methods can accurately predict occurrences of fractures and meet the need of practical application.
Shaft-lining non-mining fracture is a kind of engineering geological hazard, which results from interaction between human engineering and natural environment and could cause great economic losses. The neural network and the fuzzy neural network methods are used for forecasting and judgment of shaft-lining fractures. The results show that neural network and fuzzy neural network methods can accurately predict occurrences of fractures and meet the need of practical application.
2005, 13(2): 236-239.
The complexity of rock masses and soils leads to errors in the numerical analytical results on excavation deformation. The authors identify factors that cause such errors, discuss how those factors affect simulation results, and how the effects of such errors should be reduced to assure the accuracy of numerical simulations.
The complexity of rock masses and soils leads to errors in the numerical analytical results on excavation deformation. The authors identify factors that cause such errors, discuss how those factors affect simulation results, and how the effects of such errors should be reduced to assure the accuracy of numerical simulations.
2005, 13(2): 240-246.
Based on the seismo-geological conditions and the potential seismic risk analysis, the authors assess the potential earthquake deformation in Mogao Grottoes area using a 3-D finite element model with a parabola model for horizontal seismic displacement distribution. The seismic displacement and strain are simulated for three seismic magnitudes (Ms): 5.5, 6.0 and 6.5 under the fault activity manner of thrusting and horizontal sliding, which provides guidelines for the design of earthquake resistance and grottoes protection.
Based on the seismo-geological conditions and the potential seismic risk analysis, the authors assess the potential earthquake deformation in Mogao Grottoes area using a 3-D finite element model with a parabola model for horizontal seismic displacement distribution. The seismic displacement and strain are simulated for three seismic magnitudes (Ms): 5.5, 6.0 and 6.5 under the fault activity manner of thrusting and horizontal sliding, which provides guidelines for the design of earthquake resistance and grottoes protection.
2005, 13(2): 247-251.
The end frictional effect of a specimen can influence the plastic equivalent strain, lateral displacement and element stress-strain curve in the specimen. This paper presents gradual change forms on plastic equivalent strain and lateral displacement in various frictional coefficients, which are obtained from the simulation of the influence of the end frictional effect on a plastic equivalent strain, lateral displacement and element stress-strain curve in a plane strain using contact element in ANSYS. When friction is the minimum on the contact plane, the plot of plastic equivalent strain is two X-shaped localization bands from the upper to the lower end with a uniform distribution of lateral displacement. When friction is large on the contact plane, the plastic equivalent strain localization bands increase greatly and move towards the middle of the specimen. At the same time, the lateral displacement distribution is not uniform and the displacement in the middle is larger than those near the two ends. When the lateral displacement is restricted at both ends of the specimen, i.e., the friction is very large, the plot of plastic equivalent strain change to one X-shaped localization band, the lateral displacement distribution becomes even less uniform, and large dilation occur in the middle of the specimen.
The end frictional effect of a specimen can influence the plastic equivalent strain, lateral displacement and element stress-strain curve in the specimen. This paper presents gradual change forms on plastic equivalent strain and lateral displacement in various frictional coefficients, which are obtained from the simulation of the influence of the end frictional effect on a plastic equivalent strain, lateral displacement and element stress-strain curve in a plane strain using contact element in ANSYS. When friction is the minimum on the contact plane, the plot of plastic equivalent strain is two X-shaped localization bands from the upper to the lower end with a uniform distribution of lateral displacement. When friction is large on the contact plane, the plastic equivalent strain localization bands increase greatly and move towards the middle of the specimen. At the same time, the lateral displacement distribution is not uniform and the displacement in the middle is larger than those near the two ends. When the lateral displacement is restricted at both ends of the specimen, i.e., the friction is very large, the plot of plastic equivalent strain change to one X-shaped localization band, the lateral displacement distribution becomes even less uniform, and large dilation occur in the middle of the specimen.
2005, 13(2): 252-256.
The parameters of the slope system are uncertain and random due to slope complexity, therefore, a series of chaos can occur in the course of slope evolution. The chaotic time series method is developed based on the chaotic theory and adopted in predicting slope deformation. The development of the prediction model and its analysis are demonstrated using the case study of Xintan landslide. The results indicate that this prediction method can get a better prediction and analysis accuracy than conventional time series method.
The parameters of the slope system are uncertain and random due to slope complexity, therefore, a series of chaos can occur in the course of slope evolution. The chaotic time series method is developed based on the chaotic theory and adopted in predicting slope deformation. The development of the prediction model and its analysis are demonstrated using the case study of Xintan landslide. The results indicate that this prediction method can get a better prediction and analysis accuracy than conventional time series method.
2005, 13(2): 257-262.
Pre-stressing cable has rarely been used in supporting mining slopes even though it has been widely applied in geotechnical slope projects. This paper presents an engineering example for the application of pre-stressing cable in supporting excavated slope in the west open-pit of the Pingzhuang coalmine. Slope stability analyses are conducted under different geological conditions and supporting parameters. The results indicate that the stability of the slope is increased with the pre-stressed cable, and reinforcing parameters satisfy the requirements for safe operations. The technique has been adopted to enhance the slope stability in the mine.
Pre-stressing cable has rarely been used in supporting mining slopes even though it has been widely applied in geotechnical slope projects. This paper presents an engineering example for the application of pre-stressing cable in supporting excavated slope in the west open-pit of the Pingzhuang coalmine. Slope stability analyses are conducted under different geological conditions and supporting parameters. The results indicate that the stability of the slope is increased with the pre-stressed cable, and reinforcing parameters satisfy the requirements for safe operations. The technique has been adopted to enhance the slope stability in the mine.
2005, 13(2): 263-268.
This paper presents the concept and its calculation method of reaction degree based on the essential principles of the quantification, which extends its range of application for the primary reaction with a better scientific analysis. Taking the Zhongmacun mine as an example, the paper adopts the method of combining carving-up statistical cells and the third theory of quantification to screen 8 sensitive geological factors out of 11 geological indices that control coal and gas outburst. Based on the analysis, the regional partitions are made for the gas geology at the Zhongmacun mine. The authors then conclude that it is feasible to apply the third theory of quantification in gas geology, which offers a new insight into the filtering of geological factors for the forecast of gas outbursts.
This paper presents the concept and its calculation method of reaction degree based on the essential principles of the quantification, which extends its range of application for the primary reaction with a better scientific analysis. Taking the Zhongmacun mine as an example, the paper adopts the method of combining carving-up statistical cells and the third theory of quantification to screen 8 sensitive geological factors out of 11 geological indices that control coal and gas outburst. Based on the analysis, the regional partitions are made for the gas geology at the Zhongmacun mine. The authors then conclude that it is feasible to apply the third theory of quantification in gas geology, which offers a new insight into the filtering of geological factors for the forecast of gas outbursts.
2005, 13(2): 269-274.
This paper analyzes the deformation monitoring data in the creeping rock slope B on the left bank of Longtan Hydropower station by considering the monitoring data of ground water levels and rainfall. The results show that deformation of creeping rock slope occurs above 520 meters in the elevation, and the strong weathering line or creeping rock mass breaking face controls the rock mass deformation of slope B. With drainage and loading at the toe of the slope, deformation velocity of rock mass is gradually reduced and almost reaches a steady state over time. The authors conclude that deformation monitoring near the strong weathering line or creeping rock mass breaking face should be continued, especially during the impoundment period, and therefore surface and ground water drainage systems could thus be well maintained.
This paper analyzes the deformation monitoring data in the creeping rock slope B on the left bank of Longtan Hydropower station by considering the monitoring data of ground water levels and rainfall. The results show that deformation of creeping rock slope occurs above 520 meters in the elevation, and the strong weathering line or creeping rock mass breaking face controls the rock mass deformation of slope B. With drainage and loading at the toe of the slope, deformation velocity of rock mass is gradually reduced and almost reaches a steady state over time. The authors conclude that deformation monitoring near the strong weathering line or creeping rock mass breaking face should be continued, especially during the impoundment period, and therefore surface and ground water drainage systems could thus be well maintained.
2005, 13(2): 275-279.
Frame beams in slope protection are often analyzed for internal forces using the Winkler model. Designers usually overlook the frictional force between the frame beam and the slope. Even though the frictional resistance is much smaller than the pre-stress of an anchor bolt, it does exist. Therefore, it should not be ignored in a non-pre-stressed anchor bolt frame. This paper introduces a simple and effective method for calculating internal force with a case study. The results show that this method can help optimize design of the frame beam.
Frame beams in slope protection are often analyzed for internal forces using the Winkler model. Designers usually overlook the frictional force between the frame beam and the slope. Even though the frictional resistance is much smaller than the pre-stress of an anchor bolt, it does exist. Therefore, it should not be ignored in a non-pre-stressed anchor bolt frame. This paper introduces a simple and effective method for calculating internal force with a case study. The results show that this method can help optimize design of the frame beam.
2005, 13(2): 280-284.
This paper presents concepts on the combining engineering revetment and vegetation revetment based on systematic analysis of regular methods of slope protection. A new method - anchored frame beam revetment, is then introduced. Its revetment principles, mechanical mechanisms and construction procedures are discussed in detail.
This paper presents concepts on the combining engineering revetment and vegetation revetment based on systematic analysis of regular methods of slope protection. A new method - anchored frame beam revetment, is then introduced. Its revetment principles, mechanical mechanisms and construction procedures are discussed in detail.
2005, 13(2): 285-288.
A physicochemical reaction within a system is characterized according to particle distribution test, analysis of chemical constitution and physicochemical analysis. In addition, the structural strength of strengthened soil is tested and its microstructure is analyzed. At the end, mechanisms of improvement of serous fluid of dredger fill with additive are discussed.
A physicochemical reaction within a system is characterized according to particle distribution test, analysis of chemical constitution and physicochemical analysis. In addition, the structural strength of strengthened soil is tested and its microstructure is analyzed. At the end, mechanisms of improvement of serous fluid of dredger fill with additive are discussed.
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