Effect of Temperature Shock on Mechanical Properties and Energy Evolution of Sandstone

To explore the influence of temperature shock on the mechanical properties and energy evolution characteristics of sandstone during failure process, a series of triaxial compression tests on sandstone under different confining pressures and temperature shock were carried out. The results show that: when confining pressure is the same, with the increase of temperature shock cycles, the uncoordinated thermal expansion between mineral grains leads to a significant reduction in the stress characteristic strength and peak strength of sandstone occurring in different failure phases. During the loading process, the strain energy transformed by the external force is almost converted into elastic strain energy that can be released before the expansion stress is generated, as well as the change of dissipation energy is approximately 0. After the expansion stress is generated, the internal cracks inside the sandstone developed unstably. The strain energy transformed by the external force is slowly transformed into dissipated energy. The dissipated energy increases rapidly with the axial strain which remains at a high level in the post-peak stage. With the increase of the number of temperature shock cycles, the strain energy and elastic strain energy both decrease and the decrease amplitude becomes slower, while dissipation energy is just the opposite. The greater the dissipation energy, the more prone to cracks inside sample after expansion.