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

The dynamic constitutive model of rocks plays an important role in understanding the mechanical behavior of rocks under dynamic loads and solving rock dynamics problems. A dynamic constitutive model of rock with elastoplastic damage coupling based on continuum damage mechanics was established. This model uses the unified strength theory as the yield criterion and introduces a dynamic ratio of tension to compression to fully reflect the strain rate effect. The compressive damage variable is expressed with effective plastic strain and volumetric plastic strain, and the tensile damage variable with effective plastic strain to reflect the different damage evolution laws of rocks under tensile and compressive conditions. Using piecewise functions to characterize different plastic hardening behaviors of rocks under tensile and compressive conditions. The established constitutive model is numerically implemented of based on Fortran language and LS-DYNA user material customization interface (Umat). The established constitutive model is validated through three classic examples, namely, uniaxial and triaxial compression tests, uniaxial tensile tests, and ballistic tests on rocks. The results indicate that the constitutive model can comprehensively characterize the dynamic and static mechanical behavior of rocks.