Influence of strain energy released from a test machine on rock failure process

Rock instability occurs if the energy supplied to the rock failure process is excessive. The theoretical analysis on the energy transfer in the process of rock failure revealed that the rock failure process is a result of the strain energy released from the test machine or the surrounding rock masses of wall rock, plus the additional energy input from an external energy source if the deformation of the rock is continued and driven by the external energy source. The strain energy released from the test machine is the focus in this study because it is responsible for some of the unstable rock failures in laboratory testing. A finite element method (FEM)-based numerical experiment was carried out to study the strain energy released from test machines under different loading conditions of loading system stiffness (LSS). The modeling results demonstrated that depending on the LSS of a test machine, the strain energy released from the test machine alone without additional energy supply can drastically affect the rock failure process. The insight gained from this study can explain unstable rock failure in laboratory tests and the mechanism of some delayed rockbursts that occurred sometime after the excavation of the openings.