A dynamic damage constitutive model for rock mass with non-persistent joints under uniaxial compression

The rock mass with non-persistent joints is a kind of compound damage geological material which contains both the macroscopic flaws such as the joint and crack and the mesoscopic ones such as the microcrack and microhole. Therefore, the viewpoint that the above two kinds of flaws should be simultaneously considered in the dynamic damage constitutive model for jointed rock mass is proposed. Firstly, the classic rock dynamic damage constitutive model, based on mesoscopic dynamic fracture mechanism namely TCK model, is discussed. Secondly, aiming at the shortcoming that the geometrical parameters are only considered but the strength ones are not in the current damage variable definition, the computational formula for the macroscopic damage variable (tensor) of the jointed rock mass which can consider the geometrical and strength parameters at the same time is obtained based on the energy principle and fracture mechanics theory. Thirdly, the compound damage variable (tensor) comprehensively considering macroscopic and mesoscopic flaws based on the Lemaitre equivalent strain hypothesis is deduced. Fourthly, based on the viewpoint of the compound material mechanics proposed by others, the effect of the joint deformation parameters such as the normal and shear stiffness on the dynamic mechanical behavior of rock mass is considered. Finally, the corresponding dynamic damage constitutive model for the jointed rock mass under uniaxial compression based on TCK model is established. The effects of the strain ratio of loads, internal friction angle of joints, joint depth, shear and normal stiffnesses of joints and dip angles of joints on the dynamic mechanical behavior of rock mass are discussed using the proposed model. The calculated results fit very well the current experimental and theoretical ones, indicating the rationality of the proposed model.