Damage Failure Energy Evolution Mechanism of Jointed Sandstone Treaded with Dry-Wet Cycling Action under Triaxial Compression

In order to explore the energy dissipation mechanism of damage and failure of jointed sandstone under dry-wet cycling conditions, the triaxial compression test and rock energy dissipation theory were adopted to study the energy conversion law and the energy-driven mechanism during the deformation and failure process. The results show that the input energy U₁ from the axial pressure and the elastic strain energy U^e decrease gradually with the increase of cycles of dry-wet cycling. Specifically, the logarithmic and the linear trends were observed for the intact rock sample and the jointed rock sample, respectively. According to the evolution law of dissipated energy, the energy damage process of jointed sandstone under the loading is divided into five stages: initial damage, stable damage, stationary damage, accelerated damage and damage failure according to evolution law of dissipated energy during the process of deformation. In addition, with the increase of confining pressure, U₁ and U^e at the peak point increase linearly, the strain energy U₃ done by confining pressure and the energy U₀ absorbed by hydrostatic pressure decrease and increase linearly, respectively. The dry-wet cycling will reduce the minimum activation energy of microcrack propagation, weakening the elastic strain energy stored in the rock. This is the essential reason for the strength weakening of jointed sandstone under dry-wet cycling.