Energy evolution characteristics of deep sandstone with different true triaxial stress paths

Stress path and occurrence depth significantly affect deep rock energy evolution properties. To study this influence, true triaxial tests were conducted under various simulated depths and stress paths of initial in situ stress reduction. Energy evolution characteristics and the energy distribution process of deep sandstone were investigated. The results show the following: Under similar stress path, deep sandstone energy is positively correlated with the simulated depth. Under similar simulation depth, the energy of deep sandstone under a one-sided unloading condition of X-direction stress was greater than that under a two-sided unloading condition of X-direction stress, which, in turn, was greater than that under one-sided unloading conditions of X- and Y-direction stresses. Under similar stress path, as the Z-direction strain increases, the ratio k in deep sandstone at simulated depths of 1000 and 1500 m exhibited a trend of first increasing and then decreasing, while the ratio k of deep sandstone at a simulated depth of 2000 m first decreased, then increased, and then decreased.At the same stress path, simulated depth positively correlates with the initial energy storage and its energy storage limit of deep sandstone.The greater the depth of simulation, the pre-peak energy dissipation rate of deep sandstone decreases gradually, whereas the post-peak energy dissipation rate increases gradually.

Automated summary

Stress path and occurrence depth have significant effects on the energy evolution properties of deep rock. Triaxial tests were conducted to investigate the energy evolution characteristics and distribution process of deep sandstone under different simulated depths and stress paths. The results show that the energy of deep sandstone is positively correlated with the simulated depth under similar stress paths. The energy under one-sided unloading conditions of X-direction stress is greater than that under two-sided unloading conditions, which is greater than that under one-sided unloading conditions of X- and Y-direction stresses. The ratio k of deep sandstone exhibits different trends with increasing Z-direction strain at different simulated depths. Simulated depth is positively correlated with the initial energy storage and energy storage limit of deep sandstone under the same stress path. The pre-peak energy dissipation rate of deep sandstone decreases gradually with increasing simulated depth, while the post-peak energy dissipation rate increases gradually.