Rock instability occurs if the energy supplied to the rock failure process is excess. The theoretical analysis on the energy transfer in rock failure process 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

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... hine is focused in this study because it is responsible for some of the unstable rock failures in laboratory testing. A FEM-based numerical experiment was carried out to study the strain energy released from test machines under different loading conditions of LSS. The modeling results demonstrated that depending on the LSS of a test machine, the strain energy