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Editor Work2005 Vol. 13, No. 3
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2005, 13(3): 289-293.
Abstract
A hydropower station project is built on high mountain canyon tracts of which natural slope usually has a zestier of strong unloading rock and a zestier of ebb unloading and corresponding zone of strong (or ebb) weathering rock, and intact fresh rock in its inside. But there is a series of sheeted fracture or zone of fracture named as deep fracture. There are two deformable bodies on the right bank of the Pubugou hydropower station reservoir. This paper analyzes mechanisms of deep frctures and characteristics of deformation based on field investigation of the distribution characterization and deformation behavior. It is concluded that the deep fracture was caused by epigenetic reformation by release of high geostatic stresses. The formation age of the deep fracture is when the river changes from wide valley to canyon by stream trenching.
A hydropower station project is built on high mountain canyon tracts of which natural slope usually has a zestier of strong unloading rock and a zestier of ebb unloading and corresponding zone of strong (or ebb) weathering rock, and intact fresh rock in its inside. But there is a series of sheeted fracture or zone of fracture named as deep fracture. There are two deformable bodies on the right bank of the Pubugou hydropower station reservoir. This paper analyzes mechanisms of deep frctures and characteristics of deformation based on field investigation of the distribution characterization and deformation behavior. It is concluded that the deep fracture was caused by epigenetic reformation by release of high geostatic stresses. The formation age of the deep fracture is when the river changes from wide valley to canyon by stream trenching.
2005, 13(3): 294-299.
This paper presents results of a physical model of geo-model material under multi-stage excavation of the slope. The failure behavior of cutting slopes in layered rock mass is then analyzed. Based on finite element analysis, some key factors for stability of rock bedded slope are determined using the laminated model. The results of the numerical simulation show that the possibility of bedding slide of bedding stratified rock slope becomes very low when the intersecting angle between the strike direction of slope and that of strata exceeds 30o. Therefore, this kind of slope may not be defined as rock bedded slope. The relationship between the stability of rock bedded slope and the dip angle of strata or the shear strength of joint is also discussed in this paper.
This paper presents results of a physical model of geo-model material under multi-stage excavation of the slope. The failure behavior of cutting slopes in layered rock mass is then analyzed. Based on finite element analysis, some key factors for stability of rock bedded slope are determined using the laminated model. The results of the numerical simulation show that the possibility of bedding slide of bedding stratified rock slope becomes very low when the intersecting angle between the strike direction of slope and that of strata exceeds 30o. Therefore, this kind of slope may not be defined as rock bedded slope. The relationship between the stability of rock bedded slope and the dip angle of strata or the shear strength of joint is also discussed in this paper.
2005, 13(3): 300-304.
This paper presents a summary of geological environment, types and distribution of landslides in Qinghai as well as factors that trigger landslides. The authors also present their perspective for future development of landslide disasters.
This paper presents a summary of geological environment, types and distribution of landslides in Qinghai as well as factors that trigger landslides. The authors also present their perspective for future development of landslide disasters.
2005, 13(3): 305-309.
The Three Gorges area ranging from Yi Chang to Chongqing is located at the upstream of the Yangtze River, where the geological hazards occur at a high frequency, especially the large scale landslides developed at the bank slopes along the river. These landslides are often characterized by their large volume, extensive distribution and great complexity, which often cause serious loss and casualty in the local areas. Therefore, it is very important to understand the formation and evolution history of these major landslides so that their future development can be predicted. The distribution of major landslides in the Three Gorges is mainly controlled by lithology, geological structures and slope geometry etc. The magnitude of landslides is evidently influenced by regional geological structures. The Three Gorges area has experienced a quick tectonic uplift of 100 m since 150 ka B.P with the maximum uplift velocity of 1 mma~(-1). The frequency distribution of landslides is accordant with the rate of the crust uplift. The incision to the river valley makes the bank slope unstable and causes landslides occur during the warm and wet climatic periods. It is concluded that the dynamic factors inducing large scale landslides in this area were the coupling process of the quick tectonic uplift and climate changes. Considering the strong rainfall is the dominating triggering factor, it is suggest that the relationship between the landslides and rainfall be studied systematically.
The Three Gorges area ranging from Yi Chang to Chongqing is located at the upstream of the Yangtze River, where the geological hazards occur at a high frequency, especially the large scale landslides developed at the bank slopes along the river. These landslides are often characterized by their large volume, extensive distribution and great complexity, which often cause serious loss and casualty in the local areas. Therefore, it is very important to understand the formation and evolution history of these major landslides so that their future development can be predicted. The distribution of major landslides in the Three Gorges is mainly controlled by lithology, geological structures and slope geometry etc. The magnitude of landslides is evidently influenced by regional geological structures. The Three Gorges area has experienced a quick tectonic uplift of 100 m since 150 ka B.P with the maximum uplift velocity of 1 mma~(-1). The frequency distribution of landslides is accordant with the rate of the crust uplift. The incision to the river valley makes the bank slope unstable and causes landslides occur during the warm and wet climatic periods. It is concluded that the dynamic factors inducing large scale landslides in this area were the coupling process of the quick tectonic uplift and climate changes. Considering the strong rainfall is the dominating triggering factor, it is suggest that the relationship between the landslides and rainfall be studied systematically.
2005, 13(3): 310-315.
The section of No.212 highway in Gansu province is the most important composition of Gansus road network. Landslides and debris flows occur very often along this section. The area from Tanchang city to Wudou city is very famous for its active landslides and debris flows. This area is one of the major natural disaster areas in China. The highway goes through different geographical conditions, which causes great difference in styles and characteristics of landslides and debris flows. Based on filed observation and data collected, this paper explores the temporal and spatial variations of geomorphology and the relationship between landforms and landslides and debris flow. It provides guidelines for future design and construction of the highway.
The section of No.212 highway in Gansu province is the most important composition of Gansus road network. Landslides and debris flows occur very often along this section. The area from Tanchang city to Wudou city is very famous for its active landslides and debris flows. This area is one of the major natural disaster areas in China. The highway goes through different geographical conditions, which causes great difference in styles and characteristics of landslides and debris flows. Based on filed observation and data collected, this paper explores the temporal and spatial variations of geomorphology and the relationship between landforms and landslides and debris flow. It provides guidelines for future design and construction of the highway.
2005, 13(3): 316-319.
Owing to continuous rainstorm and fractured surrounding rock, collapse of tunnel was broken out in the cross-section YK73+955～YK73+925. Based on the analysis of field engineering geology and construction condition, ahead ductile grouting method was recommended and applied to pre-treat the surrounding rock. In order to test consolidation effect, two measurement cross sections were set up at the collapse zone. Measurement results of convergence and vault displacement show that the tunnel collapse zone was well strengthened by the ahead ductile grouting method.
Owing to continuous rainstorm and fractured surrounding rock, collapse of tunnel was broken out in the cross-section YK73+955～YK73+925. Based on the analysis of field engineering geology and construction condition, ahead ductile grouting method was recommended and applied to pre-treat the surrounding rock. In order to test consolidation effect, two measurement cross sections were set up at the collapse zone. Measurement results of convergence and vault displacement show that the tunnel collapse zone was well strengthened by the ahead ductile grouting method.
2005, 13(3): 320-324.
The occurrence and development of soil holes is the base and precondition of karst collapse, while the critical soil-hole is the final phase of its development. Whole process of the karst collapse associated with the soil hole can be divided into two phases in term of time and space: inter-collapse phase and surface-collapse phase. The inter-collapse phase is the developing and enlarging process of soil-hole in overlying soil, and the failure of overlying soil above the soil-hole is similar to the failure of apical plate surrounding rock of underground caverns. Therefore, based on the equilibrium arc theory of ММПротодьяконов, the critical height of limit equilibrium arch of overlying soil, which is the critical height of soil-hole, can be determined. A case study for the karst collapse in Tangshan Palaestra, Hebei Provinces shows a good matching between calculated critical height and observed critical height with an error of 4.3%.
The occurrence and development of soil holes is the base and precondition of karst collapse, while the critical soil-hole is the final phase of its development. Whole process of the karst collapse associated with the soil hole can be divided into two phases in term of time and space: inter-collapse phase and surface-collapse phase. The inter-collapse phase is the developing and enlarging process of soil-hole in overlying soil, and the failure of overlying soil above the soil-hole is similar to the failure of apical plate surrounding rock of underground caverns. Therefore, based on the equilibrium arc theory of ММПротодьяконов, the critical height of limit equilibrium arch of overlying soil, which is the critical height of soil-hole, can be determined. A case study for the karst collapse in Tangshan Palaestra, Hebei Provinces shows a good matching between calculated critical height and observed critical height with an error of 4.3%.
2005, 13(3): 325-329.
The Zhangjiaping landslide has multi-layers and multi-levels. To model excavation of the slope, the most typical cross-section is selected as the physical model prototype. During the experiment, the slope stability is simulated under the influence of rain by even capillary flooding method. By comparing two experiments with and without an anti-slide structure, the authors gain an insight into the destabilization mechanism of this slope, and the reinforced effect of anti-slide structure.
The Zhangjiaping landslide has multi-layers and multi-levels. To model excavation of the slope, the most typical cross-section is selected as the physical model prototype. During the experiment, the slope stability is simulated under the influence of rain by even capillary flooding method. By comparing two experiments with and without an anti-slide structure, the authors gain an insight into the destabilization mechanism of this slope, and the reinforced effect of anti-slide structure.
2005, 13(3): 330-335.
Based on the first order Taylor series expansion and finite element method, a stochastic finite element model is presented for the temperature field. The random temperature field of the frozen soil roadbed in the Bailu River section of Qinghai-Tibet Railway is calculated using the model. The simulation results show that the distribution of temperature-standard deviation is close to the temperature distribution in the roadbed, however, the standard deviation distribution inside the upper part of the roadbed presents a larger area than that of the corresponding temperature distribution. The effect of environmental temperature is remarkable at the top of the roadbed, and diminishes with depth. The values of standard deviation become uniform at the lower part of the roadbed. This paper also discusses advantages of stochastic finite element method.
Based on the first order Taylor series expansion and finite element method, a stochastic finite element model is presented for the temperature field. The random temperature field of the frozen soil roadbed in the Bailu River section of Qinghai-Tibet Railway is calculated using the model. The simulation results show that the distribution of temperature-standard deviation is close to the temperature distribution in the roadbed, however, the standard deviation distribution inside the upper part of the roadbed presents a larger area than that of the corresponding temperature distribution. The effect of environmental temperature is remarkable at the top of the roadbed, and diminishes with depth. The values of standard deviation become uniform at the lower part of the roadbed. This paper also discusses advantages of stochastic finite element method.
2005, 13(3): 336-339.
A pit slope is a human-made slope, which is a product of long-term dynamic process of excavation or extraction. Under certain circumstances, landslides are allowed within a specified range. Therefore, remediation of landslides is to assure the successful extraction of ores during the designed life time of the mine. This paper presents new concepts of a dynamic comprehensive method for remediation of landslide disasters of open pits. The paper then uses the case study of control of landslide disaster at Panluo open-pit iron mine to demonstrate the analysis procedures and applicability of the method.
A pit slope is a human-made slope, which is a product of long-term dynamic process of excavation or extraction. Under certain circumstances, landslides are allowed within a specified range. Therefore, remediation of landslides is to assure the successful extraction of ores during the designed life time of the mine. This paper presents new concepts of a dynamic comprehensive method for remediation of landslide disasters of open pits. The paper then uses the case study of control of landslide disaster at Panluo open-pit iron mine to demonstrate the analysis procedures and applicability of the method.
2005, 13(3): 340-345.
With the development of highway system in western China, more and more expressway has been built in mountainous regions. Many landslides may occur as a result of expressway construction, and could threaten the normal operation and safety of highway. In this paper, natural environment conditions and geological structural conditions of Yuanjiang-Mohei expressway in Yunnan Province are analyzed. Characteristics and risks of geological hazards along the expressway are studied. Their distribution characteristics and forming mechanism of landslides as well as its future development trends and control measures are also assessed. It is concluded that the landslides on mountainous roads are not only related to the engineering geological conditions, but also related to wrongful project designs and incorrect construction methods.
With the development of highway system in western China, more and more expressway has been built in mountainous regions. Many landslides may occur as a result of expressway construction, and could threaten the normal operation and safety of highway. In this paper, natural environment conditions and geological structural conditions of Yuanjiang-Mohei expressway in Yunnan Province are analyzed. Characteristics and risks of geological hazards along the expressway are studied. Their distribution characteristics and forming mechanism of landslides as well as its future development trends and control measures are also assessed. It is concluded that the landslides on mountainous roads are not only related to the engineering geological conditions, but also related to wrongful project designs and incorrect construction methods.
2005, 13(3): 346-352.
By using the generalized Rankine theory, the active and passive earth pressures of unsaturated soils are assessed. A new implementation method is developed and recommended, which can put the generalized Rankine theory into practice in engineering. The method can also be applied in solving other related problems in unsaturated soil mechanics, such as the bearing capacity of foundation, slope stability, etc. It will eventually provide a different way for use of the unsaturated soil mechanics in engineering.
By using the generalized Rankine theory, the active and passive earth pressures of unsaturated soils are assessed. A new implementation method is developed and recommended, which can put the generalized Rankine theory into practice in engineering. The method can also be applied in solving other related problems in unsaturated soil mechanics, such as the bearing capacity of foundation, slope stability, etc. It will eventually provide a different way for use of the unsaturated soil mechanics in engineering.
2005, 13(3): 353-360.
Based on resonance column method and dynamic triaxial tests, shear modulus and damping ratio characteristics of saturated silty soil (silt, silty sand or silty clay) in the delta of Yellow River were studied in detail. The results show that the silt content has a great influence on dynamic shear modulus. Normalized shear modulus and damping ratios vs. shear strain curves are both affected by confining pressure, and the effect of clay content is not significant. By comparing test results with the modulus reduction and damping ratio curves for sand and saturated clay suggested by Seed, once can conclude that the dynamic characteristics of deformation of the silty soil is very similar to those of sand, but there is a distinct difference. The trend of the modulus reduction and damping ratio curves from our test is also different with silty soils in other area. Modified Hardin-Drnevich models and logistic models are used to describe the trend of the normalized modulus reduction curves and damping ratios vs. shear strain curves in the paper.
Based on resonance column method and dynamic triaxial tests, shear modulus and damping ratio characteristics of saturated silty soil (silt, silty sand or silty clay) in the delta of Yellow River were studied in detail. The results show that the silt content has a great influence on dynamic shear modulus. Normalized shear modulus and damping ratios vs. shear strain curves are both affected by confining pressure, and the effect of clay content is not significant. By comparing test results with the modulus reduction and damping ratio curves for sand and saturated clay suggested by Seed, once can conclude that the dynamic characteristics of deformation of the silty soil is very similar to those of sand, but there is a distinct difference. The trend of the modulus reduction and damping ratio curves from our test is also different with silty soils in other area. Modified Hardin-Drnevich models and logistic models are used to describe the trend of the normalized modulus reduction curves and damping ratios vs. shear strain curves in the paper.
2005, 13(3): 361-366.
The determination of shear strength of expansive soil is always an important research topic due to its fissuring and over-consolidation property. The shear strength is of much significance in the design of slope in the expansive soil area. Using the expansive soil in Nanyang Area, Henan Province as an example this paper discusses in-situ shear strength test method including specimen preparation. The improved formulas for estimation of shear strength of the expansive soil are also presented. The results of landslides stability analysis indicate that the method suggested is rationale.
The determination of shear strength of expansive soil is always an important research topic due to its fissuring and over-consolidation property. The shear strength is of much significance in the design of slope in the expansive soil area. Using the expansive soil in Nanyang Area, Henan Province as an example this paper discusses in-situ shear strength test method including specimen preparation. The improved formulas for estimation of shear strength of the expansive soil are also presented. The results of landslides stability analysis indicate that the method suggested is rationale.
2005, 13(3): 367-370.
Impacting compaction is a new method to strengthen soil mass. This method has many advantages, such as high efficiency and low cost. The depth influence of impacting compaction on the foundation meets requirements of road and airfield construction. With the example of a large filled silt project, this paper discusses techniques of impacting compaction. Based on characterization of silt, the impacting compaction is made and its effectiveness is determined. At the same time, additional laboratory tests and field observation are conducted, including observation of settlement, compacting test, load-settlement test, and modulus of elasticity test. Constructed with the parameters determined by testing, the project has gained both a good compaction effect and an obvious economic benefit.
Impacting compaction is a new method to strengthen soil mass. This method has many advantages, such as high efficiency and low cost. The depth influence of impacting compaction on the foundation meets requirements of road and airfield construction. With the example of a large filled silt project, this paper discusses techniques of impacting compaction. Based on characterization of silt, the impacting compaction is made and its effectiveness is determined. At the same time, additional laboratory tests and field observation are conducted, including observation of settlement, compacting test, load-settlement test, and modulus of elasticity test. Constructed with the parameters determined by testing, the project has gained both a good compaction effect and an obvious economic benefit.
2005, 13(3): 371-375.
Centrifugal physical model test can shorten the consolidation time to 1/N2 of the prototype permeation and consolidation of clay foundation disposed by jet-grouting pile. In this paper, authors use the centrifugal physical model to estimate settlement of the soft foundation and compare the modeling results with field observation of settlement during construction and post-construction.
Centrifugal physical model test can shorten the consolidation time to 1/N2 of the prototype permeation and consolidation of clay foundation disposed by jet-grouting pile. In this paper, authors use the centrifugal physical model to estimate settlement of the soft foundation and compare the modeling results with field observation of settlement during construction and post-construction.
2005, 13(3): 376-381.
Block falls or slides are often encountered in various rock projects. To solve this problem, the stability analysis of the blocks should be done based on their geometrical conditions and relevant mechanical properties. Besides traditional projection on equatorial plane and numerical methods, a new method, coordinate projecting method, can be used in stability analyses of the blocks. After describing relevant principle, the authors provide an application of the new method in geometry analysis of the blocks and its computerization. In addition, a software CPH-1 based on the new method, has been developed by using Visual C++ language for convenience of geometry analyses. To demonstrate the effectiveness of the software, an example in underground engineering is also presented.
Block falls or slides are often encountered in various rock projects. To solve this problem, the stability analysis of the blocks should be done based on their geometrical conditions and relevant mechanical properties. Besides traditional projection on equatorial plane and numerical methods, a new method, coordinate projecting method, can be used in stability analyses of the blocks. After describing relevant principle, the authors provide an application of the new method in geometry analysis of the blocks and its computerization. In addition, a software CPH-1 based on the new method, has been developed by using Visual C++ language for convenience of geometry analyses. To demonstrate the effectiveness of the software, an example in underground engineering is also presented.
2005, 13(3): 382-388.
In this paper, authors established a critical state equation for liquefaction of soil based on the ratio of seismic shear stress and pressure stress methods (RSC) and liquefaction probability through Monte-Carlo simulation using shear strength results of 26 groups of cyclic tri-axial tests from hydroelectric power stations in Sichuan Province. The reliability of liquefaction of soil layer of one hydropower station was then evaluated using the method. The results showed that it is reasonable to classify soil as slit and sand groups for statistical analysis. The ratio of shear stress and consolidation stress (RSC) follows normal distribution. The most dangerous case is a small dam with seepage suffering grade under VII magnitude of earthquake. The liquefaction venture increases as the depth of the sand-layer increases. The most vulnerable location in soil profile is the up-side of sand-layer. Therefore, treatment measures were recommended to strengthen the foundation of the dam to prevent liquefaction.
In this paper, authors established a critical state equation for liquefaction of soil based on the ratio of seismic shear stress and pressure stress methods (RSC) and liquefaction probability through Monte-Carlo simulation using shear strength results of 26 groups of cyclic tri-axial tests from hydroelectric power stations in Sichuan Province. The reliability of liquefaction of soil layer of one hydropower station was then evaluated using the method. The results showed that it is reasonable to classify soil as slit and sand groups for statistical analysis. The ratio of shear stress and consolidation stress (RSC) follows normal distribution. The most dangerous case is a small dam with seepage suffering grade under VII magnitude of earthquake. The liquefaction venture increases as the depth of the sand-layer increases. The most vulnerable location in soil profile is the up-side of sand-layer. Therefore, treatment measures were recommended to strengthen the foundation of the dam to prevent liquefaction.
2005, 13(3): 389-397.
This paper presents a summary of development, applications and existing problems in tunnel construction of TBM for the past half a century by studying a great deal of data and projects. It is shown that TBM has become the priority of the tunnel construction method and has a great potential for future tunnel construction. From the points of rock mechanics and engineering geology, the authors analyze the engineering hazards such as TBM jamming, deformation and breakage of linings caused by large deformation of soft rock, water flow, rock burst and so on. In addition, the countermeasures adopted in construction are also discussed. With the extensive application of TBM-excavation technology in China in the near future, a better understanding of the complicated engineering geological conditions and timely adjustment of construction precepts are becoming key factors that influence construction safety and economic benefit.
This paper presents a summary of development, applications and existing problems in tunnel construction of TBM for the past half a century by studying a great deal of data and projects. It is shown that TBM has become the priority of the tunnel construction method and has a great potential for future tunnel construction. From the points of rock mechanics and engineering geology, the authors analyze the engineering hazards such as TBM jamming, deformation and breakage of linings caused by large deformation of soft rock, water flow, rock burst and so on. In addition, the countermeasures adopted in construction are also discussed. With the extensive application of TBM-excavation technology in China in the near future, a better understanding of the complicated engineering geological conditions and timely adjustment of construction precepts are becoming key factors that influence construction safety and economic benefit.
2005, 13(3): 398-403.
Because of complexity and uncertainty of landslides and limitations of prediction theory at present, it is very difficult to forecast landslides in time. This paper presents a GIS-based comprehensive landslide forecasting information system. Based on the GIS platform, the system combines quantitative forecasting based on the landslide monitoring data with qualitative forecasting on the basis of experts experience and knowledge, using an intelligent decision-making support system to make full use of knowledge base. The deformation and failure mechanisms, stability condition and failure probability of landslides can be assessed from this comprehensive system. In addition, the deformation stage and sliding time can also be predicted. Therefore, it provides useful information on landslide forecasting for decision making.
Because of complexity and uncertainty of landslides and limitations of prediction theory at present, it is very difficult to forecast landslides in time. This paper presents a GIS-based comprehensive landslide forecasting information system. Based on the GIS platform, the system combines quantitative forecasting based on the landslide monitoring data with qualitative forecasting on the basis of experts experience and knowledge, using an intelligent decision-making support system to make full use of knowledge base. The deformation and failure mechanisms, stability condition and failure probability of landslides can be assessed from this comprehensive system. In addition, the deformation stage and sliding time can also be predicted. Therefore, it provides useful information on landslide forecasting for decision making.
2005, 13(3): 404-409.
This paper present a treatment method of slope based on the EGMS (Engineering geomechanics meta-synthetic method) and characterization of the structure of natural rock mass on the left bank ship-lock slope of Wuqiangxi Hydropower Station. The author proposes a treatment solution that improves the slope stability by engineering disposal and local strengthening in addition to reducing or control external factors that causes deformation of the slope. Detailed monitoring results are also presented to demonstrate the effectiveness of the synthetic treatment. Such a successful treatment experience of the complicated slope provides a good example for engineers in the field of hydropower engineering.
This paper present a treatment method of slope based on the EGMS (Engineering geomechanics meta-synthetic method) and characterization of the structure of natural rock mass on the left bank ship-lock slope of Wuqiangxi Hydropower Station. The author proposes a treatment solution that improves the slope stability by engineering disposal and local strengthening in addition to reducing or control external factors that causes deformation of the slope. Detailed monitoring results are also presented to demonstrate the effectiveness of the synthetic treatment. Such a successful treatment experience of the complicated slope provides a good example for engineers in the field of hydropower engineering.
2005, 13(3): 410-414.
This paper presents centrifugal analogous model of the sub-soil slope and associated matching scales of some parameters. The test results from the centrifugal model experiments show that the granite residual soil slope will probably fail in two modes: plane failure and arc sliding. The effects of water content are also analyzed. The relationship of gradient and corresponding critical slope height of the slope without significant constructional surface fits Masilofo equation.
This paper presents centrifugal analogous model of the sub-soil slope and associated matching scales of some parameters. The test results from the centrifugal model experiments show that the granite residual soil slope will probably fail in two modes: plane failure and arc sliding. The effects of water content are also analyzed. The relationship of gradient and corresponding critical slope height of the slope without significant constructional surface fits Masilofo equation.
2005, 13(3): 415-418.
This paper presents reliability analyses by assuming a parabolic failure surface based on field observation of failure characteristics of high loess slopes. A design model is developed for the high loess slope accordingly and is tested using the loess high slope of Tong-Huang highway.
This paper presents reliability analyses by assuming a parabolic failure surface based on field observation of failure characteristics of high loess slopes. A design model is developed for the high loess slope accordingly and is tested using the loess high slope of Tong-Huang highway.
2005, 13(3): 419-423.
Pavement performance in widened roads has been a great concern for highway engineers in road-widening-related design and construction projects in western China since the fast implementation of West Development Strategy several years ago. The 3D finite element method (FEM) was used to simulate the construction and operation process of flexible pavements with Plaxis 3D Tunnel, a geotechnique-tailored commercial software. Elasto-plastic properties of materials as well as the filling process of subgrades in widened sections and critical placements of traffic loading were considered in the simulation. In particular, the non-uniform settlement behavior over newly-built and existing subgrades was assessed to explain premature damages of pavements commonly found in widened-road sections. Transfer functions were also used to predict the influence of widening subgrade sections on pavement responses. At the end, recommendations are made for design-construction based on results of numerical simulation.
Pavement performance in widened roads has been a great concern for highway engineers in road-widening-related design and construction projects in western China since the fast implementation of West Development Strategy several years ago. The 3D finite element method (FEM) was used to simulate the construction and operation process of flexible pavements with Plaxis 3D Tunnel, a geotechnique-tailored commercial software. Elasto-plastic properties of materials as well as the filling process of subgrades in widened sections and critical placements of traffic loading were considered in the simulation. In particular, the non-uniform settlement behavior over newly-built and existing subgrades was assessed to explain premature damages of pavements commonly found in widened-road sections. Transfer functions were also used to predict the influence of widening subgrade sections on pavement responses. At the end, recommendations are made for design-construction based on results of numerical simulation.
2005, 13(3): 424-428.
Karst caverns and faults around the railroad present a great threat to the safety of railroad tunnel construction. In this paper, the authors explored applicability of the high frequency MT method by using the stratagem~(TM) EH-4 electrical conductivity image-forming system for advance detection of the karst caverns and faults within a specified depth. At the end of the paper a case study is presented to demonstrate its application.
Karst caverns and faults around the railroad present a great threat to the safety of railroad tunnel construction. In this paper, the authors explored applicability of the high frequency MT method by using the stratagem~(TM) EH-4 electrical conductivity image-forming system for advance detection of the karst caverns and faults within a specified depth. At the end of the paper a case study is presented to demonstrate its application.
2005, 13(3): 429-432.
One of important components for a successful control and support of weak rockmasses is to have advance knowledge of engineering geological conditions and structure of surrounding rock. Therefore, lack of knowledge of engineering geological conditions and structure of surrounding rock, which leads no supported objects well defined, eventually results in failures in support of weak rockmasses. In this paper, the authors use seismic exploration technology to fully detect structures of surrounding rock in the main shaft of Xiandewang coal mine, which provides information and parameters needed for design of tunnel support.
One of important components for a successful control and support of weak rockmasses is to have advance knowledge of engineering geological conditions and structure of surrounding rock. Therefore, lack of knowledge of engineering geological conditions and structure of surrounding rock, which leads no supported objects well defined, eventually results in failures in support of weak rockmasses. In this paper, the authors use seismic exploration technology to fully detect structures of surrounding rock in the main shaft of Xiandewang coal mine, which provides information and parameters needed for design of tunnel support.
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