Energy damage evolution mechanism of non-across jointed rock mass under uniaxial compression

Energy accumulation and energy release appear evidently during the whole deformation process of jointed rock mass. In order to explore the energy evolution law of jointed rock mass under loading condition, the uniaxial compression experiment and the energy theory are adopted to study the characteristics of energy transformation of total energy U, elastic strain energy U^e and dissipation energy U^d, and to reveal the energy damage evolution mechanism of the jointed rock mass. Based on the change rate of ratio dissipated energy to elastic energy (dK/dε), the criteria for crack propagation and strength failure of non-across jointed rock mass are proposed. The obtained results show that the energy reserve of the rock mass is obviously weakened by the non-across joints, and the total energy and elastic strain energy at the peak point gradually decrease with the increase of the number of joints. The curves of elastic strain energy and dissipated energy of jointed rock mass distinctly appear “step shape” (abrupt decrease or increase), and the values that the elastic strain energy and dissipative energy of double pre-existing flaws abruptly increase or decrease are significantly smaller than those of single pre-existing flaw. The pre- and post-peak continuous mutation (dK/dε alternates between negative and positive) and mutations (dK/dε maintains as positive infinity) of dK/dε are regarded as the crack propagation and the strength failure criteria for the jointed rock mass.