Abstract: To investigate damage constitutive model of rock mass with intermittent joints in engineering practice with the assumption that the rock microscopic element strength obeys the Weibull random distribution function, the Mohr-Coulomb failure criterion is used to describe the strength of the microscopic element and the microscopic damage variable is deduced. A formula for macroscopic damage variable is deduced using energy and fracture mechanics theory and considering geometrical features and mechanical properties of the joint. Finally, based on the Lemaitre strain equivalence hypothesis, considering the macro-meso defect coupling effect, the composite damage variable is derived. A damage constitutive model of rock mass with intermittent joints under the action of macro-meso defect coupling is established based on the Mohr-Coulomb criterion. The results show that: (1) The damage model established by the Mohr-Coulomb criterion as the statistical distribution variable describing the strength of the micro-element can well reflect the characteristics of rock deformation and distribution of internal defects, which reflects that the micro-element strength of rock is influenced by the stress state. (2) The theoretical curve established by this model is in good agreement with the test curve of intermittent jointed rock mass. (3) The change of the macro damage variable and peak strength of jointed rock mass with the joint tilt angle and the change of damage variable considering the macro-meso coupling action and the peak strength of jointed rock mass with the joint tilt angle are generally consistent. (4) The relationship between the equivalent elastic moduli of macro-meso coupling and the crack connectivity rate exhibits nonlinear negative correlation. When the joint angle is constant, the relationship between the damage variable and joint length exhibits nonlinear positive correlation. When the connectivity rate is small, the relationship between the macroscopic damage variable and the internal friction angle of jointed rock mass shows a linear negative correlation, and the linear relations become nonlinear relations when the connectivity rate reaches a certain extent.

Key words: Mohr-Coulomb criterion, intermittent jointed rock mass, crack propagation, coupling, damage constitutive model