A Damage Constitutive Model for Rock Mass with Nonpersistently Closed Joints Under Uniaxial Compression

As part of the rock mass, both the macroscopic flaws such as joints and the mesoscopic flaws such as microcracks affect the strength and the deformational behavior of rock mass. Existing models can either handle any one of them alone, and a model which can consider the co-effect of these two kinds of flaws on rock mass mechanical behavior is not yet available. This study focusses on rock mass with nonpersistently closed joints and establishes a new damage constitutive model for it. Firstly, the damage model for the intact rock which contains only the mesoscopic flaws is introduced. Second, the expression of the macroscopic damage variable (tensor) which can consider the joint geometrical and mechanical properties at the same time is obtained based on the energy principle and fracture theory. Third, the damage variable based on coupling the macroscopic and mesoscopic flaws is deduced based on Lemaitre strain equivalence hypothesis, and then the corresponding damage constitutive model for rock mass with nonpersistently closed joints under uniaxial compression is set up. Finally, the test data for the intact rock under uniaxial compression are adopted to validate the proposed model. A series of calculation examples verify that the proposed model is capable of presenting the effect of joint geometrical and mechanical properties on the rock mass mechanical behavior.