Chinese Journal of Theoretical and Applied Mechani ›› 2008, Vol. 40 ›› Issue (5): 672-683.DOI: 10.6052/0459-1879-2008-5-2007-089

• Research paper • Previous Articles     Next Articles

A coupled elasto-plastic microplane damage model for jointed rock masses at great depth

  

  1. Department of Engineering Mechanics, Tsinghua University, Beijing 100084, China
  • Received:2007-02-14 Revised:2008-03-12 Online:2008-09-25 Published:2008-09-25

Abstract: Rockwall excavated at great depth often experiences large ductile deformation and may be failure due to high compressive in-situ stresses. Such phenomena are closely related to anisotropic distribution of joints in rock masses and mechanical response of the rock block and the joint. To take into account the shear resistance of joint surface and anisotropic inelastic deformation related to secondary joints formation, a coupled elasto-plastic microplane damage model for jointed rock masses is developed in the framework of microplane model and damage mechanics. Each microplane of a jointed rock mass is regarded as a binary medium, which is composed of rock and joint. Joint connectivity on the microplane is introduced as the damage variable to characterize area damage of the rock mass on that orientation due to presence of the joints. By adopting different yield function and damage evolution law for the microplane under tensile and compressive normal stress respectively, the coupled mechanisms of inelastic deformation and damage evolution are modeled. Rate form constitutive relation of stresses and strains on microplanes is developed based on classical plastic theory. According to the kinematic constraint condition of microplane model, macroscopic constitutive relation is obtained through directional integration along all microplanes. The present elasto-plastic microplane damage model is implemented to the commercial FEM software MARC through a user subroutine. Simulations with respect to the uniaxial tension and compression of jointed rock masses and problem of wellbore stability under inner mud pressure are presented respectively. It has demonstrated that the coupled effect between anisotropic inelastic deformation and damage evolution of jointed rock masses can be characterized efficiently with the model.

Key words: rock masses at great depth, joint connectivity, microplane model, damage coupled elasto-plastic, wellbore stability