Energy evolution mechanism and energy yield criterion in granite's failure process

To understand the energy evolution mechanism in the rock failure process, this paper firstly obtained the meso-mechanical parameters of granite using uniaxial compression experiments and particle flow codes, then tested the granite under different confining pressures and finally analyzed its energy evolution mechanism in the failure process and deduced its energy yield criterion. The main results are as follows: The internal damage of granite in the failure process occurs earlier under lower confining pressures while later under higher confining pressures, which shows that the internal damage under lower confining pressures is a progressive development process but under higher confining pressures the internal damage rapidly develops into failure once it occurs. The granite's elastic strain energy remains constant in a certain strain range before the peak under higher confining pressures, and the overall energy absorbed transforms into dissipation energy, which shows that the granite internal damage under higher confining pressures is more severe. The elastic strain energy increases and reaches the elastic strain energy limit and then decreases. There exists a linear relationship between the elastic strain energy limit and the confining pressure, therefore rock excavation under high confining pressures is likely to induce a rapid release of a large amount of elastic strain energy which causes the surrounding rock to become unstable and even to burst. The energy ratio at the granite's peak failure is a definite value and independent of the confining pressure. The energy yield criterion is derived based on the principle of energy. It includes lithology parameters and all principal stresses and can reflect the comprehensive factors influencing the rock failure.