2005 Vol. 27 No. 2
Abstract：
Non-uniform settlement of the part of building(box culvert) crossing the levee of Dongting-lake appears in its usable life affects its operation, and even leads to rupture. It is considered that the non-uniform settlement is caused by the weight of levee. The preservative measure is presented and used in the rebuilding of drainageway in Waiwan of Yiyang city,and the anticipated effect is obtained.
Non-uniform settlement of the part of building(box culvert) crossing the levee of Dongting-lake appears in its usable life affects its operation, and even leads to rupture. It is considered that the non-uniform settlement is caused by the weight of levee. The preservative measure is presented and used in the rebuilding of drainageway in Waiwan of Yiyang city,and the anticipated effect is obtained.
Abstract：
A large number of observation data of land subsidence and undergound water level and some results of laboratory soil test are used to analyze the deformation characteristics of soil layers in Shanghai. It’s the first time to comprehensively analyze the deformation characteristics of all soil layers and the spatial and time distribution of land subsidence caused by excessive pumping of groundwater. It is found that the deformation characteristics of soil layers are rather different from each other, and the deformation characteristic of some soil layer is different at different time and in different place. Land subsidence is influenced by many factors, so that its spatial distribution is complex. The subsidence mainly occurred in shallow soil layers before nineties of the last century, but mainly occurred in deep and shallow soil layers since nineties of the last century. The subsidence model of every soil layer can be properly developed according to these results.
A large number of observation data of land subsidence and undergound water level and some results of laboratory soil test are used to analyze the deformation characteristics of soil layers in Shanghai. It’s the first time to comprehensively analyze the deformation characteristics of all soil layers and the spatial and time distribution of land subsidence caused by excessive pumping of groundwater. It is found that the deformation characteristics of soil layers are rather different from each other, and the deformation characteristic of some soil layer is different at different time and in different place. Land subsidence is influenced by many factors, so that its spatial distribution is complex. The subsidence mainly occurred in shallow soil layers before nineties of the last century, but mainly occurred in deep and shallow soil layers since nineties of the last century. The subsidence model of every soil layer can be properly developed according to these results.
Abstract：
The sinking process of the shaft foundation under a bridge pier in Haiko has been monitored. According to the observed field data, the penetration mechanism and resistance characteristic in sinking process are systematically studied. The distribution of wall side friction and end bearing, daring penetrating into differ ent soil strata is obtained. The computing method and experimental formula of sinking coefficient K, and the value of side frictionσf, as well as reference value of earth pressure, are put forward. Then, the computation model of penetration resistance is established. The calculation formula and distribution characteristic of the maximum side friction f0 is submitted. The conclusions obtained in this paper can be used for reference of other engineering project.
The sinking process of the shaft foundation under a bridge pier in Haiko has been monitored. According to the observed field data, the penetration mechanism and resistance characteristic in sinking process are systematically studied. The distribution of wall side friction and end bearing, daring penetrating into differ ent soil strata is obtained. The computing method and experimental formula of sinking coefficient K, and the value of side frictionσf, as well as reference value of earth pressure, are put forward. Then, the computation model of penetration resistance is established. The calculation formula and distribution characteristic of the maximum side friction f0 is submitted. The conclusions obtained in this paper can be used for reference of other engineering project.
2005, 27(2): 153-156.
Abstract：
In the paper, four new types of composite soil nailing walls are introduced. These composite walls include combinations of soil nailing with prestressed anchors, with cut-off wall (deep mixing piles or jet grouting piles) and prestressed anchors, with micropiles and prestressed anchors, and with prestressed anchors, cut-off wall and micropiles. Conditions under which each of the four combinations is applicable are stated in detail. Design and methods using a circular sliding surface to check the overall stability and the method of pullout resistance of soil nailing are presented. The structural characteristics of soil nail, cut-off wall, prestressed anchor and micropile are also introduced. Finally, a successful example using composite soil nailing wall is described. In this example, the composite soil nailing was used as a shoring system for deep foundation pit excavation at a site where difficult geological conditions exist.
In the paper, four new types of composite soil nailing walls are introduced. These composite walls include combinations of soil nailing with prestressed anchors, with cut-off wall (deep mixing piles or jet grouting piles) and prestressed anchors, with micropiles and prestressed anchors, and with prestressed anchors, cut-off wall and micropiles. Conditions under which each of the four combinations is applicable are stated in detail. Design and methods using a circular sliding surface to check the overall stability and the method of pullout resistance of soil nailing are presented. The structural characteristics of soil nail, cut-off wall, prestressed anchor and micropile are also introduced. Finally, a successful example using composite soil nailing wall is described. In this example, the composite soil nailing was used as a shoring system for deep foundation pit excavation at a site where difficult geological conditions exist.
Abstract：
This paper presents experimental data obtained during the construction and loading test of an oil tank , which was constructed by SINOPEC Maoming Petrochemical Company. Currently, this oil tank is the largest in China. The tank was founded on loose sand improved with stone columns. Pressure cell and piezometers were used to monitor soil stresses and pore pressures respectively. At the same time the deformation of the soil foundation was observed. The obtained result was analyzed thoroughly.
This paper presents experimental data obtained during the construction and loading test of an oil tank , which was constructed by SINOPEC Maoming Petrochemical Company. Currently, this oil tank is the largest in China. The tank was founded on loose sand improved with stone columns. Pressure cell and piezometers were used to monitor soil stresses and pore pressures respectively. At the same time the deformation of the soil foundation was observed. The obtained result was analyzed thoroughly.
Abstract：
A new type of fiber optic sensor is developed for detecting the pore-water pressure in freeway foundation, which is embedded in the foundation of the Guang-Wu freeway to monitor construction of soft soil foundation. Fiber optic Bragg gating is contained in these sensors to detect the value of the pressure exactly and become sensitive to fluctuating of the water pressure. In this experiment, problems of the building, embedding and data collection etc of the measuring system are solved. In order to appraising the new sensor, we compared the collected data of the fiber optic sensor to those of the conventional sensors. By analyzing the data collected, we appraise the effect of soft soil foundation treatment, then compare the result to the actual situation to find whether the sensors reflect the real condition. The result shows that these sensors can not only achieve the same effect of the conventional sensors but also overcome some deficiencies of the conventional ones, and the development of this new fiber optic sensor is successful.
A new type of fiber optic sensor is developed for detecting the pore-water pressure in freeway foundation, which is embedded in the foundation of the Guang-Wu freeway to monitor construction of soft soil foundation. Fiber optic Bragg gating is contained in these sensors to detect the value of the pressure exactly and become sensitive to fluctuating of the water pressure. In this experiment, problems of the building, embedding and data collection etc of the measuring system are solved. In order to appraising the new sensor, we compared the collected data of the fiber optic sensor to those of the conventional sensors. By analyzing the data collected, we appraise the effect of soft soil foundation treatment, then compare the result to the actual situation to find whether the sensors reflect the real condition. The result shows that these sensors can not only achieve the same effect of the conventional sensors but also overcome some deficiencies of the conventional ones, and the development of this new fiber optic sensor is successful.
Abstract：
In this paper, the dipole of memory points in scaled one-dimensional memory model would be generalized as a memory surface in multidimensional stress space. The scale modulus is defined as the distance between the current stress point and failure surface, and the scale function of one–dimensional stress-strain relationship is adopted in multidimensional scaled memory model. The interpolation method of scale modulus would be composed, after that the plastic modulus of any point on hysteretic loop could be estimated. A program with FEM has been completed, and it will be applied to the dynamic nonlinear analysis of earth structure under multidimensional stress state. Through the simulation of the dynamic triaxial test with specimen of 300mm diameter, it is demonstrated that the dynamic stress-strain relationship could be simulated commendably by multidimensional scale memory model and its algorithm.
In this paper, the dipole of memory points in scaled one-dimensional memory model would be generalized as a memory surface in multidimensional stress space. The scale modulus is defined as the distance between the current stress point and failure surface, and the scale function of one–dimensional stress-strain relationship is adopted in multidimensional scaled memory model. The interpolation method of scale modulus would be composed, after that the plastic modulus of any point on hysteretic loop could be estimated. A program with FEM has been completed, and it will be applied to the dynamic nonlinear analysis of earth structure under multidimensional stress state. Through the simulation of the dynamic triaxial test with specimen of 300mm diameter, it is demonstrated that the dynamic stress-strain relationship could be simulated commendably by multidimensional scale memory model and its algorithm.
Abstract：
Conventional finite element procedures with equal order interpolations for dynamic u-p formulation of saturated soils have been experiencing numerical difficulties for the problems concerning with small permeability and neglectable compressibility of pore-fluid. This paper discusses the stabilization techniques based on the staggered implicit-implicit algorithm and direct α -method to overcome the above mentioned difficulties. Attentions will be paid to the steady state formulations resulted from both approaches. Based on the steady state formulations, the paper will then discuss the determination of the local stabilization parameters, with which a significant improvement for the obtained solutions of pore-pressure can be achieved. Finally, two numerical examples regarding saturated soils subject to a surface cyclic loading are presented to illustrate the effectiveness of the proposed techniques.
Conventional finite element procedures with equal order interpolations for dynamic u-p formulation of saturated soils have been experiencing numerical difficulties for the problems concerning with small permeability and neglectable compressibility of pore-fluid. This paper discusses the stabilization techniques based on the staggered implicit-implicit algorithm and direct α -method to overcome the above mentioned difficulties. Attentions will be paid to the steady state formulations resulted from both approaches. Based on the steady state formulations, the paper will then discuss the determination of the local stabilization parameters, with which a significant improvement for the obtained solutions of pore-pressure can be achieved. Finally, two numerical examples regarding saturated soils subject to a surface cyclic loading are presented to illustrate the effectiveness of the proposed techniques.
Abstract：
A new cyclic constitutive model for granular soil material has been presented within the general framework of bounding surface plasticity. In this model the volumetric strain due to stress-dilatancy for a granular material is composed of reversible and irreversible dilatancy components. The former is characterized by its reversibility and dependency on the magnitude and direction of the current shear stress, and conversely, the latter by its irreversibility and dependency on past shear history. New mechanisms and formulation have been presented for description of the reversible and irreversible dilatancy. Influence of the irreversible and reversible dilatancy component on the stress-strain response was also investigated. The effectiveness of the model was verified with comparison between the calculated and observed results.
A new cyclic constitutive model for granular soil material has been presented within the general framework of bounding surface plasticity. In this model the volumetric strain due to stress-dilatancy for a granular material is composed of reversible and irreversible dilatancy components. The former is characterized by its reversibility and dependency on the magnitude and direction of the current shear stress, and conversely, the latter by its irreversibility and dependency on past shear history. New mechanisms and formulation have been presented for description of the reversible and irreversible dilatancy. Influence of the irreversible and reversible dilatancy component on the stress-strain response was also investigated. The effectiveness of the model was verified with comparison between the calculated and observed results.
Abstract：
Presented in this paper is a one-dimensional computational model for numerical simulation of migration process of pollutants in waste landfills which can take both the sorption of aquifer and bio-degradation of wastes into consideration. The model, for the case of a clay liner of finite depth, can simulate the complex migration mechanisms including advection and dispersion transport as well as geochemical reaction. Based on the computational model, numerical solutions are achieved by using semi-analytical procedure. Then through comparative parametric studies, the key factors which considerably control the migration process of containments are defined based on the numerical results. It is shown that for most practical situations the concentration of contaminant within the groundwater beneath landfill will gain its peak value at a specific time and subsequently will decrease with time. It is found that the most important factors affecting the migration process of pollutants include the thickness and permeability of the clay liner, sorption capacities of both aquifer and clay liner.
Presented in this paper is a one-dimensional computational model for numerical simulation of migration process of pollutants in waste landfills which can take both the sorption of aquifer and bio-degradation of wastes into consideration. The model, for the case of a clay liner of finite depth, can simulate the complex migration mechanisms including advection and dispersion transport as well as geochemical reaction. Based on the computational model, numerical solutions are achieved by using semi-analytical procedure. Then through comparative parametric studies, the key factors which considerably control the migration process of containments are defined based on the numerical results. It is shown that for most practical situations the concentration of contaminant within the groundwater beneath landfill will gain its peak value at a specific time and subsequently will decrease with time. It is found that the most important factors affecting the migration process of pollutants include the thickness and permeability of the clay liner, sorption capacities of both aquifer and clay liner.
Abstract：
Based on the test results of acoustic emission parameters in laboratory and on site, evaluating criterion of relative strength-weakness characteristic based on the acoustic emission parameters of rockmass stability is presented. Not only the acoustic emission patameters in failure process are considered, but also the evaluating criterion are dealed with in standard. Then, the effect of the environmental factors are eliminated. So, the evaluating criterion of rockmass stability are more effective.
Based on the test results of acoustic emission parameters in laboratory and on site, evaluating criterion of relative strength-weakness characteristic based on the acoustic emission parameters of rockmass stability is presented. Not only the acoustic emission patameters in failure process are considered, but also the evaluating criterion are dealed with in standard. Then, the effect of the environmental factors are eliminated. So, the evaluating criterion of rockmass stability are more effective.
Abstract：
Continuous conductivity imaging system of EH-4 is the update numeral instrument with electromagnetic method. With regard to the spectral leak problem of EH-4 system caused by Fourier transform of limited time and discrete sampling, the frequency spectrum characteristics of EH-4 signals in Fourier transform under the different windows and their influence on signal analysis are discussed. Different windows indicate the characteristics of the different sides of signal, and have the different merits and defects respectively. Analysis and interpretation of EH-4 signals done in different windows will be complete and authentic.
Continuous conductivity imaging system of EH-4 is the update numeral instrument with electromagnetic method. With regard to the spectral leak problem of EH-4 system caused by Fourier transform of limited time and discrete sampling, the frequency spectrum characteristics of EH-4 signals in Fourier transform under the different windows and their influence on signal analysis are discussed. Different windows indicate the characteristics of the different sides of signal, and have the different merits and defects respectively. Analysis and interpretation of EH-4 signals done in different windows will be complete and authentic.
Abstract：
Based on the principle of effective stress and nonlinear Darcy’s law for gas, three-dimensional elasto-plastic model for sand production with coupled stress and pressure is established, which is solved by the nonlinear finite element method. According to results obtained with the numerical code, distributions of effective plastic strain, pressure, and velocity are investigated. The maximum effective strain occurs at the top and bottom of the starting position of perforations; the stable pressure looks like irregular funnel, and the gas velocity increases dramatically with the its maximum value occurring at the end of perforations. From the distributions of effective plastic strain and velocity, sand production in gas reservoirs is controlled by the effective stress; and steep increase in gas velocity due to pressure dependency is the important affecting factor. Meanwhile, high formation pressure will reduce the possibility of sand production. For gas reservoirs with high pressure, to maintain high formation pressure, to stabilize the bottom hole pressure and to keep this pressure below the limit value would help to reduce the amount of sand production.
Based on the principle of effective stress and nonlinear Darcy’s law for gas, three-dimensional elasto-plastic model for sand production with coupled stress and pressure is established, which is solved by the nonlinear finite element method. According to results obtained with the numerical code, distributions of effective plastic strain, pressure, and velocity are investigated. The maximum effective strain occurs at the top and bottom of the starting position of perforations; the stable pressure looks like irregular funnel, and the gas velocity increases dramatically with the its maximum value occurring at the end of perforations. From the distributions of effective plastic strain and velocity, sand production in gas reservoirs is controlled by the effective stress; and steep increase in gas velocity due to pressure dependency is the important affecting factor. Meanwhile, high formation pressure will reduce the possibility of sand production. For gas reservoirs with high pressure, to maintain high formation pressure, to stabilize the bottom hole pressure and to keep this pressure below the limit value would help to reduce the amount of sand production.
Abstract：
The dynamic and static strength of frozen silty clay are studied based on the results of the low-temperature dynamic and static triaxial test with samples taken from Qinghai-Tibet Railway. It is indicated that both of the dynamic and static strength increase with the decreasing temperature, and decrease with the increasing water content.The variation of static cohesion(c), dynamic cohesion (cd), static friction angle (φ) and dynamic friction angle (φd) is same as that of strength. The dynamic strength increases with the increasing confining pressure. The static deformation is divided into elastic and plastic stages. The static strength increases with the increasing confining pressure in the plastic stage, but there no such evidence in elastic stage. The increasing rate of static strength is slow and the plastic flow occurs in plastic stage. Dynamic friction angle decrease with the increasing vibration times, however dynamic cohesion varies slightly.
The dynamic and static strength of frozen silty clay are studied based on the results of the low-temperature dynamic and static triaxial test with samples taken from Qinghai-Tibet Railway. It is indicated that both of the dynamic and static strength increase with the decreasing temperature, and decrease with the increasing water content.The variation of static cohesion(c), dynamic cohesion (cd), static friction angle (φ) and dynamic friction angle (φd) is same as that of strength. The dynamic strength increases with the increasing confining pressure. The static deformation is divided into elastic and plastic stages. The static strength increases with the increasing confining pressure in the plastic stage, but there no such evidence in elastic stage. The increasing rate of static strength is slow and the plastic flow occurs in plastic stage. Dynamic friction angle decrease with the increasing vibration times, however dynamic cohesion varies slightly.
Abstract：
In order to avoid the corrosion of steel anchors in ground engineering, since 1990, FRP anchors, a non-metallic anchors, are used abroad to substitute for the traditional steel anchors. FRP anchors have the characteristics of higher tensile strength, better antisepsis, light weight, heat expansion coefficient near to concrete and mortar, et al. It is the first time that FRP anchors are tested in China. Based on pull-out tests of 63 specimens, interface bond strength between FRP anchors and different media are systematically studied, and the results show that FRP anchors have higher interface bond strength. This conclusion can provide verifications and references for the application of FRP anchors in ground engineering.
In order to avoid the corrosion of steel anchors in ground engineering, since 1990, FRP anchors, a non-metallic anchors, are used abroad to substitute for the traditional steel anchors. FRP anchors have the characteristics of higher tensile strength, better antisepsis, light weight, heat expansion coefficient near to concrete and mortar, et al. It is the first time that FRP anchors are tested in China. Based on pull-out tests of 63 specimens, interface bond strength between FRP anchors and different media are systematically studied, and the results show that FRP anchors have higher interface bond strength. This conclusion can provide verifications and references for the application of FRP anchors in ground engineering.
2005, 27(2): 210-213.
Abstract：
For the treatment of various water conservancies, not only the feasibility of a new type of grout has been studied theoretically, but also the experiments on properties of new types of grout, such as mobility, cohesion, penetrability, strength, avirulence ,non-corrosion and so on are performed in the lab and some ideal results achieved.
For the treatment of various water conservancies, not only the feasibility of a new type of grout has been studied theoretically, but also the experiments on properties of new types of grout, such as mobility, cohesion, penetrability, strength, avirulence ,non-corrosion and so on are performed in the lab and some ideal results achieved.
2005, 27(2): 214-218.
Abstract：
With the development of highway construction, more and more slopes need to be tackled with better anchors. Reliable anchorage effect is one of the important factors for a stable slope. Grouting material plays an important role in providing more powerful, more stable and more endurable anchorage capability. Many laboratory and in situ tests have been performed with a new type of mortar mixing with the fibers. It has been found that the application of the fiber mortar improves the cohesive strength between the mortar and the surrounding rocks and the crack resistant strength of the anchorages. Furthermore, an elasto-plastic finite element program has been applied to simulating the process of anchorages action. Analyzing results show that the fibre mortar can prevent the anchorage from cracking and improve bearing capacity.
With the development of highway construction, more and more slopes need to be tackled with better anchors. Reliable anchorage effect is one of the important factors for a stable slope. Grouting material plays an important role in providing more powerful, more stable and more endurable anchorage capability. Many laboratory and in situ tests have been performed with a new type of mortar mixing with the fibers. It has been found that the application of the fiber mortar improves the cohesive strength between the mortar and the surrounding rocks and the crack resistant strength of the anchorages. Furthermore, an elasto-plastic finite element program has been applied to simulating the process of anchorages action. Analyzing results show that the fibre mortar can prevent the anchorage from cracking and improve bearing capacity.
Abstract：
Land subsidence caused by excessive exploitation of groundwater , has occurred in many cities of our country and thereout leads to great environmental problem and economy loss. The problems of forecast and control of land subsidence must be solved in these cites . Based on the mechanism of land subsidence ,the information system of 3D visualized model for Quaternary strata is constructed on the GMS platform .The system can intuitively and veritably show the spatial outspread shape and spatial combination feature of strata with different properties .Also, the following information such as the strata separation and combination, cut and display of sections, section at the appointed depth, observation of the strata in different visual angle, can be handily displayed by the three dimensional visualized strata model. The strata model can provide valuable information and favorable conditions for the research of land subsidence.
Land subsidence caused by excessive exploitation of groundwater , has occurred in many cities of our country and thereout leads to great environmental problem and economy loss. The problems of forecast and control of land subsidence must be solved in these cites . Based on the mechanism of land subsidence ,the information system of 3D visualized model for Quaternary strata is constructed on the GMS platform .The system can intuitively and veritably show the spatial outspread shape and spatial combination feature of strata with different properties .Also, the following information such as the strata separation and combination, cut and display of sections, section at the appointed depth, observation of the strata in different visual angle, can be handily displayed by the three dimensional visualized strata model. The strata model can provide valuable information and favorable conditions for the research of land subsidence.
Abstract：
Cement-soil retaining wall (CSRW) was usually designed on the basis of the trial and error method, which was not only complicated, but also difficult to find out the reliable and economic solution. In this paper the optimization design method of CSRW was discussed, and an optimization mathematic model for CSRW was set up, which took the effective width, the embedded depth and the replacement ratio of CSRW as its decision variables. Genetic algorithms (Gas) were introduced to optimize the design of CSRW, and the influence of structure parameters of CSRW on the optimization design was discussed. Two examples were given to verify the presented method. The comparison of computated results show that the reliable and economical design can be obtained by the proposed method.
Cement-soil retaining wall (CSRW) was usually designed on the basis of the trial and error method, which was not only complicated, but also difficult to find out the reliable and economic solution. In this paper the optimization design method of CSRW was discussed, and an optimization mathematic model for CSRW was set up, which took the effective width, the embedded depth and the replacement ratio of CSRW as its decision variables. Genetic algorithms (Gas) were introduced to optimize the design of CSRW, and the influence of structure parameters of CSRW on the optimization design was discussed. Two examples were given to verify the presented method. The comparison of computated results show that the reliable and economical design can be obtained by the proposed method.
Abstract：
The geological conditions are complex in Longtan hydroelectric project. The strata are dipping steeply and the faults are developed. The caverns are constituented with long span and high side wall. So the stability of surrounding rock mass is very important during excavation. In this paper, the excavation and support of caverns are numerical simulated by fast Lagrangian method (FLAC) according to the designer’s scheme. Numerical results of two profiles considering excavation with support are compared and analyzed. Finally some useful conclusions are obtained.
The geological conditions are complex in Longtan hydroelectric project. The strata are dipping steeply and the faults are developed. The caverns are constituented with long span and high side wall. So the stability of surrounding rock mass is very important during excavation. In this paper, the excavation and support of caverns are numerical simulated by fast Lagrangian method (FLAC) according to the designer’s scheme. Numerical results of two profiles considering excavation with support are compared and analyzed. Finally some useful conclusions are obtained.
