Dynamic fracture and deformation responses of rock mass specimens containing 3D printing rough joint subjected to impact loading

Flaws including joints and fissures in the surrounding rock of deep caverns are usually characterized by irregularity and roughness, and are also vulnerable to dynamic loads in addition to the static loads of in-situ stress. In this study, rock specimens with a filling rough joint were prepared by the 3D printing technology and rock-like materials. In addition, dynamic impact tests were conducted on the jointed rock masses with the split Hopkinson pressure bar (SHPB) system. The influence of the impact strain rate and joint roughness coefficient (JRC) against the failure process and dynamic mechanical properties of the specimens were investigated through the digital image correlation (DIC) method together with high-speed camera. The findings indicate that the dynamic mechanical parameters for joint rock masses are of high sensitivity to impact strain rate and JRC. The failure strain, dynamic compressive strength, failure energy and dynamic elastic modulus all increase with increasing JRC and strain rate, and are generally linearly related to the strain rate. Under dynamic loading, microcracks first appear near the tip of the rough joint and continue to develop along the joint direction, ultimately creating the main fracture surface. The vertical strain band first appears near the rough joint and finally follows the joint direction throughout the entire specimen, while the horizontal strain occurs near the rough joint surface, mainly caused by the shear slip on both sides of the joint surface. With the growth of strain rate, the propagation rate of the strain band also grows, and the failure degree of the rock mass progressively intensifies.