Study on the Guiding Law of Holes on the Crack Propagation Behavior under Impact Load

There are a large number of primary and regenerated defects in the rock mass of deep underground engineering, such as primary joints, regenerated cracks and geological holes. When the cracks are subjected to external loads, especially dynamic loads, the dynamic fracture phenomenon will occur. The uncontrolled propagation of cracks will further aggravate the fragmentation of roadway surrounding rock and reduce its stability. To this end, this article simplifies geological fractures into a prefabricated crack and anchor bolt drilling into a single circular hole, thus constructing three types of single crack single hole board experimental configurations (SCSH) with horizontal, vertical, and single hole size variations. The Split Hopkinson Pressure Bar test system (SHPB) is used to explore the influence of single hole on the dynamic fracture behavior of cracks under dynamic load. The effect of physical experiment is verified by the explicit dynamic software AUTODYN, and its influence mechanism is further explored. The results show: (1) as the distance between the circular hole and the tip of the pre-crack increases along the crack direction and propagates to the vicinity of the circular hole, the propagation path tends to the hole; (2) as the increase of vertical distance between hole and pre-crack, the guiding stress field at the tip of the propagating crack and the guiding effect of the hole on the crack are both gradually decrease; (3) with the diameter increase of the hole, which presents a significant guiding phenomenon for the crack dynamic propagation, however, when the hole diameter is less than a certain value, it will have no guiding effect on crack propagation. The research results of this paper can provide strong theoretical support for the corresponding prevention and control measures to ensure the stability of roadway surrounding rock in underground impact pressure mines.