Damage characteristics and energy-dissipation mechanism of frozen–thawed sandstone subjected to loading

To reveal the energy-dissipation mechanism of the rock deformation and destruction process under the influence of freeze–thaw cycles and investigate the essence of rock freeze–thaw damage, the evolution characteristics of the total strain energy, elastic energy, and dissipated energy in the sandstone failure process are analysed according to the energy principle, number of freeze-thaw cycles, and uniaxial compression. The results reveal that: (1) the evolution behaviours of the total strain energy, elastic energy, and dissipative energy of sandstone under different numbers of freeze–thaw cycles are similar; that is, the total strain energy and elastic energy gradually increase with the increasing strain, and the elastic energy decreases sharply after reaching the peak limit. The dissipative energy gradually increases and thereafter remains stable; finally, it rapidly increases. (2) With increasing freeze–thaw cycles, the growth rates of the total strain energy, elastic energy, and dissipated energy gradually decrease, whereas the energy value at the peak first increases and then decreases. The energy distribution during rock loading is affected by the number of freeze-thaw cycles (defined as N ). When N is <30, the proportion of dissipation energy in the compacting section first increases and then decreases linearly; the decreasing rate decreases gradually with an increase in N . When N is larger than 30, the dissipation energy ratio linearly decreases as the strain increases, and the decreasing rate increases as N increases. (3) According to the dissipative energy ratio evolution characteristics of rock failure, the peak strength and peak strain damage evolution models of frozen−thawed rocks are established. The fitting results indicate that the model has a good correlation with the experimental data and can accurately reflect the peak strength and peak strain evolution of frozen−thawed rocks.