On the basis of the sufficient consideration of vectorial characteristics of stress, a new nonlinear constitutive model for cohesionless soil under plane strain and 3-D conditions was presented in a way that the actio...On the basis of the sufficient consideration of vectorial characteristics of stress, a new nonlinear constitutive model for cohesionless soil under plane strain and 3-D conditions was presented in a way that the action effects of stress vector are decomposed into the action effect of mean effective stress and that of the stress ratio vector (ratio of deviatoric stress vector to mean effective stress). The constitutive model can take account of the influence of both numerical and directional changes of stress vector on deformation of soil simultaneously, and is applicable of both static and dynamic loading.展开更多
The stress vector-based constitutive model for cohesionless soil, proposed by SHI Hong-yan et al., was applied to analyze the deformation behaviors of materials subjected to various stress paths. The result of analysi...The stress vector-based constitutive model for cohesionless soil, proposed by SHI Hong-yan et al., was applied to analyze the deformation behaviors of materials subjected to various stress paths. The result of analysis shows that the constitutive model can capture well the main deformation behavior of cohesionless soil, such as stress-strain nonlinearity, hardening property, dilatancy, stress path dependency, non-coaxiality between the principal stress and the principal strain increment directions, and the coupling of mean effective and deviatoric stress with deformation. In addition, the model can also take into account the rotation of principal stress axes and the influence of intermediate principal stress on deformation and strength of soil simultaneously. The excellent agreement between the predicted and measured behavior indicates the comprehensive applicability of the model.展开更多
Series of testing on coarse grained soils were carried out with a true triaxial testing apparatus. The loads were applied from the major principal and minor principal directions, respectively, to simulate the construc...Series of testing on coarse grained soils were carried out with a true triaxial testing apparatus. The loads were applied from the major principal and minor principal directions, respectively, to simulate the construction and water impounding process of a rock fill dam. The stress and strain relationships induced by the different loading methods were investigated. A remarkable stress-induced anisotropy under complex stress state was observed. Contrary to popular assumptions in traditional numerical analysis and constitutive models, it was found that different elastic modulus and Poisson ratio exist in different principal directions in rock fill dams. From the testing results, an anisotropic constitutive model based on Duncan-Chang nonlinear model is presented to overcome the limitations of axi-symmetric assumptions in conventional triaxial experiments and constitutive models. Both models were then applied in FEM analysis of an under-construction earth core high rock soil filled dam with the focus on hydraulic fracturing. The study reveals the major biases that exist when numerical analysis and constitutive models do not give serious consideration to the intermediate principal stress and anisotropy effects in soil rock built structures.展开更多
Here is proposed the principle of interaction between plastic volumetric and shear strains, revealing the main origin of generating the complexity and variety of deformations for geotechnical materials. Here are also ...Here is proposed the principle of interaction between plastic volumetric and shear strains, revealing the main origin of generating the complexity and variety of deformations for geotechnical materials. Here are also explained the manners of the interaction between plastic volumetric and shear strains and the conditions of generating shear dilatancy. It is demonstrated that dependency of the stress path exists and is a combination of effects of this interaction. According to this principle, it is theoretically proved that the space critical state line exists, and is unique and independent of the stress history. Based on this principle, the constitutive models that are able completely and accurately to characterize the basic behavior features for geotechnical materials have been constructed within the framework of thermodynamics. What is determined is a general expression of the constitutive relation as well as the inequality of the dissipative potential increment for obeying the second law of thermodynamics.展开更多
A constitutive model that can describe the damage evolution of anisotropic metal sheets during the complex forming processes which experience wide stress triaxiality history is essential to accurately predict the defo...A constitutive model that can describe the damage evolution of anisotropic metal sheets during the complex forming processes which experience wide stress triaxiality history is essential to accurately predict the deformation and rupture behaviors of the processes.In this study,a modified Lemaitre damage criterion which couples with the anisotropic Barlat 89 yield function is established.The effects of stress triaxiality,Lode parameter and shear stress on damage accumulation are considered in the constitutive model.The model is numerically implemented and applied to fracture prediction in tensile tests with different stress triaxialities and a complex deformation process with wide stress triaxiality history.The good consistency of predictions and experiments indicates that the modified Lemaitre damage model has excellent fracture prediction ability.Finally,the accuracy of the model is analyzed and discussed.展开更多
In order to consider the stress path dependency of soils,this paper decomposes any arbitrary stress path into several infinitesimal stress paths.Then the infinitesimal stress path is further transformed into the super...In order to consider the stress path dependency of soils,this paper decomposes any arbitrary stress path into several infinitesimal stress paths.Then the infinitesimal stress path is further transformed into the superposition of two parts,i.e..a constant stress ratio part and a constant mean stress part,which arc sufficiently close to the real stress path.T he plastic strain increments under the transformed paths arc determined separately,and then the plastic strain under any path is obtained.Based on the instantaneous loading line of normally consolidated soil,a reference state line is proposed to determine the overconsolidation ratio and creep time of soil.The overconsolidation ratio is introduced into the viscous How rule to obtain the viscous strain increment.The strcss-strain-timc relationship for triaxial compression condition is extended to 3D stress condition by the transformed stress method.The proposed model adopts only seven material parameters and each of them has a clear physical meaning.Comparisons with test results demonstrate that the model can not only reasonably predict the plastic strain under typical stress paths of excavation,but adequately capture the time-dependent behaviours of soils,including creep,stress relaxation and strain rate effect.展开更多
文摘On the basis of the sufficient consideration of vectorial characteristics of stress, a new nonlinear constitutive model for cohesionless soil under plane strain and 3-D conditions was presented in a way that the action effects of stress vector are decomposed into the action effect of mean effective stress and that of the stress ratio vector (ratio of deviatoric stress vector to mean effective stress). The constitutive model can take account of the influence of both numerical and directional changes of stress vector on deformation of soil simultaneously, and is applicable of both static and dynamic loading.
文摘The stress vector-based constitutive model for cohesionless soil, proposed by SHI Hong-yan et al., was applied to analyze the deformation behaviors of materials subjected to various stress paths. The result of analysis shows that the constitutive model can capture well the main deformation behavior of cohesionless soil, such as stress-strain nonlinearity, hardening property, dilatancy, stress path dependency, non-coaxiality between the principal stress and the principal strain increment directions, and the coupling of mean effective and deviatoric stress with deformation. In addition, the model can also take into account the rotation of principal stress axes and the influence of intermediate principal stress on deformation and strength of soil simultaneously. The excellent agreement between the predicted and measured behavior indicates the comprehensive applicability of the model.
基金Project(50809023)supported by the National Natural Science Foundation of ChinaProject(2015B17714)supported by the Fundamental Research Funds for Central Universities,China
文摘Series of testing on coarse grained soils were carried out with a true triaxial testing apparatus. The loads were applied from the major principal and minor principal directions, respectively, to simulate the construction and water impounding process of a rock fill dam. The stress and strain relationships induced by the different loading methods were investigated. A remarkable stress-induced anisotropy under complex stress state was observed. Contrary to popular assumptions in traditional numerical analysis and constitutive models, it was found that different elastic modulus and Poisson ratio exist in different principal directions in rock fill dams. From the testing results, an anisotropic constitutive model based on Duncan-Chang nonlinear model is presented to overcome the limitations of axi-symmetric assumptions in conventional triaxial experiments and constitutive models. Both models were then applied in FEM analysis of an under-construction earth core high rock soil filled dam with the focus on hydraulic fracturing. The study reveals the major biases that exist when numerical analysis and constitutive models do not give serious consideration to the intermediate principal stress and anisotropy effects in soil rock built structures.
文摘Here is proposed the principle of interaction between plastic volumetric and shear strains, revealing the main origin of generating the complexity and variety of deformations for geotechnical materials. Here are also explained the manners of the interaction between plastic volumetric and shear strains and the conditions of generating shear dilatancy. It is demonstrated that dependency of the stress path exists and is a combination of effects of this interaction. According to this principle, it is theoretically proved that the space critical state line exists, and is unique and independent of the stress history. Based on this principle, the constitutive models that are able completely and accurately to characterize the basic behavior features for geotechnical materials have been constructed within the framework of thermodynamics. What is determined is a general expression of the constitutive relation as well as the inequality of the dissipative potential increment for obeying the second law of thermodynamics.
基金co-supported by the National Science Fund for Distinguished Young Scholars of China(No.51625505)the National Natural Science Foundation of China(Nos.U1910213 and U1937203)the Independent Research Project of State Key Laboratory of Solidification Processing of Northwestern Polytechnical University(No.2019-TZ-02)。
文摘A constitutive model that can describe the damage evolution of anisotropic metal sheets during the complex forming processes which experience wide stress triaxiality history is essential to accurately predict the deformation and rupture behaviors of the processes.In this study,a modified Lemaitre damage criterion which couples with the anisotropic Barlat 89 yield function is established.The effects of stress triaxiality,Lode parameter and shear stress on damage accumulation are considered in the constitutive model.The model is numerically implemented and applied to fracture prediction in tensile tests with different stress triaxialities and a complex deformation process with wide stress triaxiality history.The good consistency of predictions and experiments indicates that the modified Lemaitre damage model has excellent fracture prediction ability.Finally,the accuracy of the model is analyzed and discussed.
基金supported by the National Natural Science Foundation of China(Grant Nos.U1839201,51778026,51421005&51538001).
文摘In order to consider the stress path dependency of soils,this paper decomposes any arbitrary stress path into several infinitesimal stress paths.Then the infinitesimal stress path is further transformed into the superposition of two parts,i.e..a constant stress ratio part and a constant mean stress part,which arc sufficiently close to the real stress path.T he plastic strain increments under the transformed paths arc determined separately,and then the plastic strain under any path is obtained.Based on the instantaneous loading line of normally consolidated soil,a reference state line is proposed to determine the overconsolidation ratio and creep time of soil.The overconsolidation ratio is introduced into the viscous How rule to obtain the viscous strain increment.The strcss-strain-timc relationship for triaxial compression condition is extended to 3D stress condition by the transformed stress method.The proposed model adopts only seven material parameters and each of them has a clear physical meaning.Comparisons with test results demonstrate that the model can not only reasonably predict the plastic strain under typical stress paths of excavation,but adequately capture the time-dependent behaviours of soils,including creep,stress relaxation and strain rate effect.
