Stress-Confinement Effect on the Dynamic Mechanical Properties of Heterogeneous Granite Under Impact Loading: Experimental and Numerical Simulation

To investigate the stress-confinement effect on the dynamic crack propagation and energy evolution characteristics of heterogeneous granite under impact loading, a three-dimensional equivalent grain-based model (3D-GBM) and FLAC(3D)-PFC3D coupled modeling technique was used to establish a numerical model of a full-scale true triaxial Hopkinson test system. The results indicate that: (1) A rate-effect model of the dynamic strength enhancement factor for heterogeneous rocks under multiaxial static and dynamic combined loading was constructed, with lateral stress confinement enhancing the sensitivity of dynamic strength to the strain rate. (2) Axial stress reduces the crack initiation stress ratio (sigma(ci)/sigma(d)) and damage stress threshold ratio (sigma(cd)/sigma(d)), reducing the time to their onset, while lateral stress has the opposite effect. (3) Lateral stress confinement helps dynamically adjust the types of microcracks within the rock, restricts the relative slip friction between particles, and decreases the kinetic energy of failure. (4) At approximately the same strain rate, the strain energy and slip friction energy sequentially increase under uniaxial, biaxial, and triaxial stress confinement. The mutual slip friction and movement between rock particles are more intense under biaxial stress confinement compared to uniaxial conditions.