Experimental study on spalling of deep rock under half sine stress wave disturbance

For the spalling failure phenomenon of deep rock under the action of stress wave disturbance, based on the one-dimensional elastic wave theory, the propagation mechanism of a simple half sine stress wave in a single rock member is clarified, and the spalling failure principle is analyzed theoretically. According to the characteristic factors such as pure tensile stress and dynamic tensile strength, the failure process is characterized. In advance, the SHPB equipment is used to carry out the spalling tests on the rock. It is found that the failure fracture surface of the rock bar after spalling is relatively neat, and it is basically vertical to the tensile stress direction, which means that it is the typical type I tensile failure. Moreover, the spalling length is consistent with the theoretical analysis value. With the increase of spalling times, the fracture length of rock member will gradually increase. Furthermore, the essential reason of rock spalling is analyzed, showing that it is caused by the interaction and coupling of two main factors, i.e., the dynamic effects caused by strong disturbance and the structural effects reflected by the inhomogeneity, non-linear elasticity and anisotropy of rock specimens. The inherent nature of failure behaviors of a rock case revealed in this study can provide corresponding theoretical support for the refined excavation and support design of geotechnical engineering, rock burst warning and monitoring, etc. It also can provide certain theoretical significance and engineering application prospect for the strong dynamic disturbance behaviors and progressive instability failure phenomena of deep underground engineering.