Theoretical study on fracture mechanism of rock bridge considering crack plastic propagation

Abstract

Abstract The research on the fracture mechanism of rock bridge is helpful to better understanding the failure process of rocks. In this paper, in order to study the influence of wing crack propagation on the stability of rock bridges, a new maximum plastic zone size fracture criterion is established according to the extension of plastic zone accompanied by crack propagation. Based on the new crack fracture criterion, a corresponding critical judgment condition is proposed considering the influence of multi-crack interaction on the wing crack propagation. Then, the fracture mechanism of rock bridges from the perspective of plastic zone extension was explored based on three different crack distribution models (cracks of equal length in parallel). It was found that the fracture mode of the rock bridge is deeply influenced by the dip angle of the rock bridge in the case where the rock bridge is of equal length to the pre-existing crack. The contact speed and contact mode of plastic zone varies for different dip angles of the rock bridge, but all the contact of plastic zone will eventually cause plastic yielding in the rock bridge zone. And then, the secondary cracks always start to propagate in the range of the plastic zone formed by the wing cracks, and eventually the rock bridge forms a macroscopic fracture damage due to the propagation of the secondary cracks.