A constitutive model for methane hydrate-bearing sediment(MHBS)is essential for the analysis of mechanical response of MHBS to the change of hydrate saturation caused by gas extraction. A new elasto-plastic constituti...A constitutive model for methane hydrate-bearing sediment(MHBS)is essential for the analysis of mechanical response of MHBS to the change of hydrate saturation caused by gas extraction. A new elasto-plastic constitutive model is built in order to simulate the mechanical behavior of MHBS in this paper. This model represents more significant mechanical properties of MHBS such as bonding, higher stiffness, softening and stress-strain nonlinear relationship. The bonding behavior can be described by use of a parameter related to mechanical hydrate saturation. Higher stiffness can be modeled by the introduction of hydrate saturation into traditional expression of soil stiffness. Softening can be controlled by a function describing the relationship between cohesion and bonding structure factor. Dilatancy can be estimated by establishing the relationship between the lateral strain and axial strain. Meanwhile, the hypothesis of isotropic expanding is applied to the calculation of the volumetric strain. The stress-strain curves under different hydrate saturation conditions predicted by the proposed model are in good agreement with the test data. All the coefficients can be easily obtained by the triaxial test of MHBS.展开更多
A new double-yield-sarface （DYS） model was developed to characterize the strength and deformation behaviors of coarse granular materials （CGMs）. Two kinds of deformation mechanisms, including the shear and compres...A new double-yield-sarface （DYS） model was developed to characterize the strength and deformation behaviors of coarse granular materials （CGMs）. Two kinds of deformation mechanisms, including the shear and compressive plastic deformation, were taken into account in this model, These two deformation mechanisms were described by the shear and compressive yield functions, respectively. The Lode angle dependent formulations of proposed model were deduced by incorporating a 3D nonlinear unified failure criterion. Some comparisons were presented between the numerical predictions of proposed model and test data of true triaxial tests on the modeled rockfills. The model predictions are in good agreement with the test data and capture the strain hardening and plastic volumetric dilation of CGMs. These findings verify the reasonability of current DYS model, and indicate that this model is well suited to reproduce the stress-strain-volume change behavior of CGMs in general.展开更多
An adaptive criterion for shear yielding as well as shear failure of soils is proposed in this paper to address the fact that most criteria,including the Mohr-Coulomb criterion,the Lade criterion and the Matsuoka-Naka...An adaptive criterion for shear yielding as well as shear failure of soils is proposed in this paper to address the fact that most criteria,including the Mohr-Coulomb criterion,the Lade criterion and the Matsuoka-Nakai criterion,cannot agree well with the experimental results when the value of the intermediate principal stress parameter is too big.The new criterion can adjust an adaptive parameter based on the experimental results in order to make the theoretical calculations fit the test results more accurately.The original elliptic-parabolic yield surface model can capture both soil contraction and dilation behaviors.However,it normally over-predicts the soil strength due to its application of the Extended Mises criterion.A new elliptic-parabolic yield surface mode is presented in this paper,which introduces the adaptive criterion in three-dimensional principal stress space.The new model can well model the stress-strain behavior of soils under general stress conditions.Compared to the original model which can only simulate soil behavior under triaxial compression conditions,the new model can simulate soil behaviors under both triaxial compression conditions and general stress conditions.展开更多
The traditional unified viscoplasticity constitutive model can be only applied to metal materials.The study of the unified constitutive theory for metal materials has discovered the correlation between the classical p...The traditional unified viscoplasticity constitutive model can be only applied to metal materials.The study of the unified constitutive theory for metal materials has discovered the correlation between the classical plasticity theory and the unified viscoplasticity constitutive model,thus leading to the con-cepts of the classic plastic potential and yield surface in the unified constitutive model.Moreover,this research has given the continuous expression of the classical plastic multiplier and presented the corresponding constructive method,which extends its physical significance and lays down a good foundation for the application of the unified constitutive theory to the material analysis in more fields.This paper also introduces the unified constitutive model for metal materials and geo-materials.The numerical simulation indicates that the construction should be both reasonable and practical.展开更多
基金Supported by the National Science and Technology Major Project of China(No.2011ZX05026-004)the National Natural Science Foundation of China(No.51309047 and No.51509032)
文摘A constitutive model for methane hydrate-bearing sediment(MHBS)is essential for the analysis of mechanical response of MHBS to the change of hydrate saturation caused by gas extraction. A new elasto-plastic constitutive model is built in order to simulate the mechanical behavior of MHBS in this paper. This model represents more significant mechanical properties of MHBS such as bonding, higher stiffness, softening and stress-strain nonlinear relationship. The bonding behavior can be described by use of a parameter related to mechanical hydrate saturation. Higher stiffness can be modeled by the introduction of hydrate saturation into traditional expression of soil stiffness. Softening can be controlled by a function describing the relationship between cohesion and bonding structure factor. Dilatancy can be estimated by establishing the relationship between the lateral strain and axial strain. Meanwhile, the hypothesis of isotropic expanding is applied to the calculation of the volumetric strain. The stress-strain curves under different hydrate saturation conditions predicted by the proposed model are in good agreement with the test data. All the coefficients can be easily obtained by the triaxial test of MHBS.
基金Project(50825901)supported by the National Natural Science Foundation for Distinguished Young Scholar of ChinaProject(2009492011)supported by State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering,Nanjing Hydraulic Research Institute,China+1 种基金Project(GH200903)supported by Key Laboratory of Ministry of Education for Geomechanics and Embankment Engineering(Hohai University),ChinaProject(Y1090151)supported by Natural Science Foundation of Zhejiang Province,China
文摘A new double-yield-sarface （DYS） model was developed to characterize the strength and deformation behaviors of coarse granular materials （CGMs）. Two kinds of deformation mechanisms, including the shear and compressive plastic deformation, were taken into account in this model, These two deformation mechanisms were described by the shear and compressive yield functions, respectively. The Lode angle dependent formulations of proposed model were deduced by incorporating a 3D nonlinear unified failure criterion. Some comparisons were presented between the numerical predictions of proposed model and test data of true triaxial tests on the modeled rockfills. The model predictions are in good agreement with the test data and capture the strain hardening and plastic volumetric dilation of CGMs. These findings verify the reasonability of current DYS model, and indicate that this model is well suited to reproduce the stress-strain-volume change behavior of CGMs in general.
基金supported by the National Natural Science Foundation for Distinguished Young Scholar(Grant No.50825901)the Public ServiceSector R&D Project of Ministry of Water Resource of China(Grant No.200801014)the Fundamental Research Funds for the Central Universities
文摘An adaptive criterion for shear yielding as well as shear failure of soils is proposed in this paper to address the fact that most criteria,including the Mohr-Coulomb criterion,the Lade criterion and the Matsuoka-Nakai criterion,cannot agree well with the experimental results when the value of the intermediate principal stress parameter is too big.The new criterion can adjust an adaptive parameter based on the experimental results in order to make the theoretical calculations fit the test results more accurately.The original elliptic-parabolic yield surface model can capture both soil contraction and dilation behaviors.However,it normally over-predicts the soil strength due to its application of the Extended Mises criterion.A new elliptic-parabolic yield surface mode is presented in this paper,which introduces the adaptive criterion in three-dimensional principal stress space.The new model can well model the stress-strain behavior of soils under general stress conditions.Compared to the original model which can only simulate soil behavior under triaxial compression conditions,the new model can simulate soil behaviors under both triaxial compression conditions and general stress conditions.
基金Supported by the National Natural Science Foundation of China (Grant No. 90410012)
文摘The traditional unified viscoplasticity constitutive model can be only applied to metal materials.The study of the unified constitutive theory for metal materials has discovered the correlation between the classical plasticity theory and the unified viscoplasticity constitutive model,thus leading to the con-cepts of the classic plastic potential and yield surface in the unified constitutive model.Moreover,this research has given the continuous expression of the classical plastic multiplier and presented the corresponding constructive method,which extends its physical significance and lays down a good foundation for the application of the unified constitutive theory to the material analysis in more fields.This paper also introduces the unified constitutive model for metal materials and geo-materials.The numerical simulation indicates that the construction should be both reasonable and practical.
