Experimental study on crack propagation and the coalescence of rock-like materials with two preexisting fissures under biaxial compression

Rock masses consist of rock and fissures, and fissures in rock masses play an important role in rock mass stability. In this paper, rock-like materials with preexisting fissures were prepared, and then, the specimens were subjected to biaxial compression. The lateral stress contained two categories: 1.0 MPa and 2.0 MPa. During the experiments, strain gauges were distributed on the surface of the specimens, and a digital camera was used to record the process of crack propagation. Through the experiments, it can be found that the rock bridge coalescence mode can be generally classified into three categories; meanwhile, the influence of the preexisting fissure angle, rock bridge angle, and lateral stress due to crack propagation was specifically analyzed. Consequently, the strain concentration of the tips of preexisting fissures was calculated and discussed.