Experimental research on the non-linear energy characteristics of granite and sandstone

Abstract

Multi-stage cyclic loading–unloading triaxial compression (MCLTC) tests of granite and red sandstone were performed to study the non-linear characteristics of energy dissipation and energy storage evolution in rock under triaxial compression (TC) with various confining pressures. The failure mode of granite and red sandstone during MCLTC testing was shear failure, which was consistent with the TC failure model. This indicated that the MCLTC path had little effect on the rock failure characteristics. The non-linear evolution characteristics of the input (Uo), elastic (Ue) and dissipated (Ud) energy densities under various confining pressures were analysed. The results showed that Uo, Ue and Ud increase non-linearly with the strain. In addition, a linear relationship between the cumulative dissipated energy, cumulative elastic energy density, and cumulative input energy density was proposed. The cumulative dissipated energy densities at peak compressive strength can be obtained due to the linear law of cumulative energy. A fitting relationship was proposed for calculating the peak strength and peak strain. The results showed that the peak strength and peak strain under various confining pressures increase with the cumulative Ue, cumulative Ud and cumulative Uo.