Numerical study of fracture failure nature around the circular and horseshoe openings using the bonded-particle model

Abstract

SUMMARY Rock failure is a process of the rapid release of energy. The energy release can generate a transient elastic wave. This phenomenon is named acoustic emission (AE) that can provide a wealth of information regarding the failure process. To get a better understanding of failure mechanism in rocks, several criteria had been proposed and widely used to distinguish the failure nature of fractures based on the AE information. Due to these criteria are based on different theories, sometimes they may obtain different results from the same failure source. To analyse the application of these distinguished criteria, a series of uniaxial compressive tests were carried out on granite rocks containing a circular/horseshoe opening by using bonded-particle model combined with the AE technique. Cracking sequences and failure pattern of numerical simulations are comparable with those of laboratory tests. By discussing the force distribution, displacement field and the forces acting on the failure sources of numerical study, the results indicate that the crack path initiating from the top and bottom of the opening is tensile in nature. The shear and compressive AE events are predominant at the lateral sides of the opening. Three criteria can well distinguish the tensile failure. While the Ohtsu's criterion cannot distinguish the compressive failure effectively. The Feignier and Young's criterion and Ming's criterion are recommended to studying the cracking process and failure nature of rocks.