Experimental analysis of the height–diameter ratio effect of rock energy under uniaxial cyclic loading–unloading conditions.

The deformation-to-failure process of rock is accompanied by the dissipation and release of energy and is the result of the mutual conversion of energy. The uniaxial compression and uniaxial cyclic loading–unloading testing of rock samples with eight height–diameter ratios (size) was performed using the MTS 816 rock mechanics testing system to determine the effect of the height–diameter ratio on the rock strength, energy accumulation, and dissipation. The influence rules of the height–diameter ratio on the uniaxial compressive strength, deformation parameters, and failure mode of the rock samples were analyzed. The total, elastic, and dissipated energy densities absorbed by the rock samples with various height–diameter ratios were obtained through calculation, and the evolution and distribution rules of the size effect on energy accumulation and dissipation were revealed. The energy density of rock samples with various height–diameter ratios increased nonlinearly with the increase in the cycle index or axial stress, whereas the energy density of the rock sample decreased with the increase in the height–diameter ratio. At the pre-peak stage, the elastic energy accumulated in the rock samples was higher than the dissipated energy, and the proportion of the elastic energy density was greater. With the increase in the height–diameter ratio of the rock sample, the proportion of elastic energy approximately increased, and the proportion of dissipated energy decreased. [ABSTRACT FROM AUTHOR]