In this study consecutive consolidated isotropically drained triaxial tests for the coefficient of earth pressure at rest(K_0) were carried out to investigate its rules of evolution as well as its strength characteris...In this study consecutive consolidated isotropically drained triaxial tests for the coefficient of earth pressure at rest(K_0) were carried out to investigate its rules of evolution as well as its strength characteristics for normal,consolidated saturated silt under high pressure.The tests results indicate that:1) for normal,consolidated saturated silt,K_0 values increase as the consolidation stress increases at high pressure levels,while the nonlinear characteristics of K_0 are inconspicuous compared to cohesive soils;2) the Jaky and Roscoe equations,used to calculate K_0,are only suitable for certain soils,but cannot represent these values for normal, consolidated saturated silt due to the variation in bilinear strength at high pressure;and 3) there are close relations between the nonlinear characteristics of K_0 and the void ratio,measured in the tests.Both share the same functional form while under pressure. Based on our experimental results,we developed an empirical linear model to interpret the rules of nonlinear variation for the coefficient of earth pressure at rest.展开更多
In order to obtain the earth pressure coefficient at rest (K0) at higher consolidation pressures during secondary compression, a series of K0 tests for saturated reconstituted clay were conducted. The results indicate...In order to obtain the earth pressure coefficient at rest (K0) at higher consolidation pressures during secondary compression, a series of K0 tests for saturated reconstituted clay were conducted. The results indicate that the measured K0 in secondary compression can be described by equations related to internal friction angle, secondary compression coefficient, compression index, recompression index, and sediment time. Effects of consolidation pressures and sediment time on K0 during secondary compression can be attributed to cementation (part of cohesion) increase and internal friction angle decrease. Cementation increase leads to nonlinear variation for K0 and internal friction angle decrease results in increase of K0. K0 computed by equations associated with internal friction angle is overestimated at apparent lower consolidation pressures with different sediment time, which agrees with the measured values well at apparent higher consolidation pressures.展开更多
According the Coulomb earth pressure theory,it is obtained that,for normally consolidated soils,the lateral pressure coefficient of a soil at rest is equal to 1,and it is independent of the soil type,either granular o...According the Coulomb earth pressure theory,it is obtained that,for normally consolidated soils,the lateral pressure coefficient of a soil at rest is equal to 1,and it is independent of the soil type,either granular or cohesive;or that the material is in a loose or compact state;hard or a soft cohesive soil.Also,a methodology to calculate the earth pressure for intermediate states between at rest condition and the active pressure is presented.In addition,a methodology to calculate the earth pressure for intermediate states between at rest condition and the passive pressure is presented.Two practical examples are presented:one for a frictionless wall;and another for a coarse wall.Practical recommendations are given for the use of the lateral earth pressure coefficient for different applications.展开更多
The most common apparatus used to investigate the load-deformation parameters of homogeneous fine-grained soils is a Casagrande-type oedometer. A typical Casagrande oedometer cell has an internal diameter of 76 mm and...The most common apparatus used to investigate the load-deformation parameters of homogeneous fine-grained soils is a Casagrande-type oedometer. A typical Casagrande oedometer cell has an internal diameter of 76 mm and a height of 19 mm.However, the dimensions of this kind of apparatus do not meet the requirements of some civil engineering applications like studying load-deformation characteristics of specimens with large-diameter particles such as granular materials or municipal solid waste materials. Therefore, it is decided to design and develop a large-scale oedometer with an internal diameter of 490 mm. The new apparatus provides the possibility to evaluate the load-deformation characteristics of soil specimens with different diameter to height ratios. The designed apparatus is able to measure the coefficient of lateral earth pressure at rest. The details and capabilities of the developed oedometer are provided and discussed. To study the performance and efficiency, a number of consolidation tests were performed on Firoozkoh No. 161 sand using the newly developed large scale oedometer made and also the 50 mm diameter Casagrande oedometer. Benchmark test results show that measured consolidation parameters by large scale oedometer are comparable to values measured by Casagrande type oedometer.展开更多
Construction of urban tunnels requires the control of surface subsidence to minimize any disturbance to nearby buildings and services. Past study of surface subsidence has been limited to mainly empirical solutions ba...Construction of urban tunnels requires the control of surface subsidence to minimize any disturbance to nearby buildings and services. Past study of surface subsidence has been limited to mainly empirical solutions based on field studies, and very few analytical studies have been carried out. The available analytical solutions are not sufficient to include complex ground conditions; hence, a comprehensive analytical solution coupled with numerical modeling is necessary to model the effect of surface subsidence due to tunneling. This paper presents the results of modeling of surface settlements due to tunneling using the finite element method. The effect of the overconsolidation ratio of soils expressed in terms of the co- efficient of earth pressure at rest （K0） on surface subsidence due to tunneling is investigated. It is demonstrated that surface settlements appear to be sensitive to K0 values, and for geotechnical calculations pertaining to overconsolidated sand and clay soil, K0 values of 0.6 and 0.8, respectively, are proposed.展开更多
基金Financial support for this work,provided by the National Natural Science Foundation of China (No.50534040)the Project of the Science and Technology Ministry of China(No.2006BAB16B01)the Post Graduate Research Project of Jiangsu Province (No.CX08B_103Z),
文摘In this study consecutive consolidated isotropically drained triaxial tests for the coefficient of earth pressure at rest(K_0) were carried out to investigate its rules of evolution as well as its strength characteristics for normal,consolidated saturated silt under high pressure.The tests results indicate that:1) for normal,consolidated saturated silt,K_0 values increase as the consolidation stress increases at high pressure levels,while the nonlinear characteristics of K_0 are inconspicuous compared to cohesive soils;2) the Jaky and Roscoe equations,used to calculate K_0,are only suitable for certain soils,but cannot represent these values for normal, consolidated saturated silt due to the variation in bilinear strength at high pressure;and 3) there are close relations between the nonlinear characteristics of K_0 and the void ratio,measured in the tests.Both share the same functional form while under pressure. Based on our experimental results,we developed an empirical linear model to interpret the rules of nonlinear variation for the coefficient of earth pressure at rest.
基金Projects(50534040, 50974117) supported by the National Natural Science Foundation of ChinaProject(20110491489) supported by China Postdoctoral Science FoundationProject(2011QNA03) supported by Fundamental Research Funds for Central Universities, China
文摘In order to obtain the earth pressure coefficient at rest (K0) at higher consolidation pressures during secondary compression, a series of K0 tests for saturated reconstituted clay were conducted. The results indicate that the measured K0 in secondary compression can be described by equations related to internal friction angle, secondary compression coefficient, compression index, recompression index, and sediment time. Effects of consolidation pressures and sediment time on K0 during secondary compression can be attributed to cementation (part of cohesion) increase and internal friction angle decrease. Cementation increase leads to nonlinear variation for K0 and internal friction angle decrease results in increase of K0. K0 computed by equations associated with internal friction angle is overestimated at apparent lower consolidation pressures with different sediment time, which agrees with the measured values well at apparent higher consolidation pressures.
文摘According the Coulomb earth pressure theory,it is obtained that,for normally consolidated soils,the lateral pressure coefficient of a soil at rest is equal to 1,and it is independent of the soil type,either granular or cohesive;or that the material is in a loose or compact state;hard or a soft cohesive soil.Also,a methodology to calculate the earth pressure for intermediate states between at rest condition and the active pressure is presented.In addition,a methodology to calculate the earth pressure for intermediate states between at rest condition and the passive pressure is presented.Two practical examples are presented:one for a frictionless wall;and another for a coarse wall.Practical recommendations are given for the use of the lateral earth pressure coefficient for different applications.
基金financial support provided by the Iran University of Science and Technology
文摘The most common apparatus used to investigate the load-deformation parameters of homogeneous fine-grained soils is a Casagrande-type oedometer. A typical Casagrande oedometer cell has an internal diameter of 76 mm and a height of 19 mm.However, the dimensions of this kind of apparatus do not meet the requirements of some civil engineering applications like studying load-deformation characteristics of specimens with large-diameter particles such as granular materials or municipal solid waste materials. Therefore, it is decided to design and develop a large-scale oedometer with an internal diameter of 490 mm. The new apparatus provides the possibility to evaluate the load-deformation characteristics of soil specimens with different diameter to height ratios. The designed apparatus is able to measure the coefficient of lateral earth pressure at rest. The details and capabilities of the developed oedometer are provided and discussed. To study the performance and efficiency, a number of consolidation tests were performed on Firoozkoh No. 161 sand using the newly developed large scale oedometer made and also the 50 mm diameter Casagrande oedometer. Benchmark test results show that measured consolidation parameters by large scale oedometer are comparable to values measured by Casagrande type oedometer.
文摘Construction of urban tunnels requires the control of surface subsidence to minimize any disturbance to nearby buildings and services. Past study of surface subsidence has been limited to mainly empirical solutions based on field studies, and very few analytical studies have been carried out. The available analytical solutions are not sufficient to include complex ground conditions; hence, a comprehensive analytical solution coupled with numerical modeling is necessary to model the effect of surface subsidence due to tunneling. This paper presents the results of modeling of surface settlements due to tunneling using the finite element method. The effect of the overconsolidation ratio of soils expressed in terms of the co- efficient of earth pressure at rest （K0） on surface subsidence due to tunneling is investigated. It is demonstrated that surface settlements appear to be sensitive to K0 values, and for geotechnical calculations pertaining to overconsolidated sand and clay soil, K0 values of 0.6 and 0.8, respectively, are proposed.
