Study on the damage constitutive model of rock considering the influence of dynamic ratio of tension to compression

Based on continuum damage mechanics, a rock dynamic constitutive model with coupled elastic-plastic damage was established. This model took the unified strength theory as the yield criterion and introduces the dynamic tensile-compressive ratio to fully reflect the strain rate effect. The effective plastic strain and volumetric plastic strain were used to represent the compressive damage variable, and the effective plastic strain was used to represent the tensile damage variable, thereby reflecting the different damage evolution laws of rocks under tensile and compressive conditions. A piecewise function was adopted to describe the different plastic hardening behaviors of rocks under tensile and compressive conditions. The established constitutive model was numerically implemented based on Fortran language and the LS-DYNA user material customization interface (Umat). The established constitutive model is verified by three classical calculation examples, namely, the uniaxial and triaxial compression tests of rocks, the uniaxial tensile test of rocks, and the ballistic test of rocks. The results showed that this constitutive model can comprehensively describe the static and dynamic mechanical behaviors of rocks.