Representation of brittle rock plasto-elastic behaviour based on tangible cracks in discontinuous deformation analysis

Abstract

Micro-cracks, which are prevalent in crustal rock masses, can significantly affect the physical and mechanical properties of rocks. The closure of micro-cracks explains the initial non-linear stress–strain curves observed during compression in brittle rocks. In this study, the plasto-elastic deformation was implemented through crack closure in the discontinuous deformation analysis (DDA). Tangible micro-cracks were formed by updating the vertex positions as opposed to setting the virtual gap and width. These micro-cracks were arranged randomly, but still adhered to specific crack parameters (crack intensity, aspect ratio, and dip-angle distribution). The uniaxial compression simulation results verified that these micro-cracks could open and close under external stress and execute the crack-closure stage. The results indicated that the increase in crack intensity primarily decreased the ratio of the initial to elastic moduli, and the crack aspect ratio was approximately equal to the crack-closure strain. An inhomogeneous dip-angle distribution led to anisotropic plasto-elastic deformation owing to the different numbers of cracks perpendicular to the axial stress. According to previous theories and reasonable assumptions, a function between the crack parameters and crack-closure stress was first established. Finally, the experimental results for two specific rocks were reproduced using this method, which can be applied to research on rock properties or rock mass engineering influenced by crack closures.