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《Journal of Hohai University(Natural Sciences)》 2018-06
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Modelling the time-dependent strain softening behavior of rock with an elasto-viscoplastic constitutive model

WANG Zhichao;ZHOU Ding;WANG Weiguo;HU Qian;Hunan Key Laboratory of Geomechanics and Engineering Safety,Xiangtan University;College of Civil Engineering and Mechanics,Xiangtan University;  
In order to describe the strain softening behavior and time-dependent characteristics of rock,an elastoviscoplastic constitutive model is proposed considering the influence of time-dependent strain softening behavior.The new model was based on the sub-loading surface theory of over-consolidated soil and adopted the Hashiguchi's sub-loading yield surface as a referenced yield surface. Besides,a relative overstress relation is used to obtain the dynamic loading surface at any strain rate based on the referenced yield surface. Two material parameters,c0 and m',which are related to the rate sensitivity,were added into the new model,and they can be determined by triaxial compression tests with different strain rates. The expansion index κ and compression index λ in the original model were replaced by elastic modulus E0 and deformation modulus Edrespectively,combining the characteristics of rock. A dynamic equilibrium condition,using the current stress,viscoplastic strain and viscoplastic strain rate as state variables,was adopted as a convergence criterion. After that,this model has been implemented into ABAQUS with the Newton-Raphson iteration. Simulations on the rate sensitivity triaxial tests of rock were conducted to verify the proposed model. The results show that the predicted results of model are in good agreement with experimental data. Meanwhile,material parameters are easy to understand and measure with clear physical meaning. Therefore,the proposed model can be used in the finite element calculation of complex boundary value problems.
【Fund】: 国家自然科学基金(51308485);; 湖南省自然科学基金(2016JJ2133);; 湖南省教育厅优秀青年项目(17B260)
【CateGory Index】: TU45
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