Acoustic emission and energy evolution of sandstone failure subjected to deep mining stress

Deep mining stress has an important impact on acoustic emission characteristics and energy evolution law of rock during its deformation and damage. With sandstone as research object, true triaxial loading-unloading experiments were performed under different hydrostatic stress (mining depth) and Lode angles (mining stress path) (-30°-30°). The results have shown that hydrostatic stress and Lode angle have great influence on the deformation and strength of sandstone. With the same hydro-static stress, the increase of Lode angle promotes expansion and penetration of micro-cracks and reduces bearing capacity of sandstone, making the destruction more rapidly and intensely. With the same Lode angle, the principal strain in three directionsincreases with hydro-static stress increasing, and the ductility of sandstone is enhanced. Furthermore, specimens encounter unstable failure at large deformation. The acoustic emission parameters are in good correspondence with each loading-unloading stage of sandstone. AF (average-frequency) and RA (the ratio of rise time and amplitude) in different stages have great differences, indicating different damage types in each stage. Meanwhile, the shearing effect is more obvious when the sandstone is closer to the peak failure point. In addition, the damage evolution is well displayed by energy conversion characteristics of rock. The energy consumption ratio m (the ratio of dissipated energy Ud and total energy U) tends to decrease first, then keeps constant, and finally increases. The increment of m in the strain-hardening stage is almost same, and rock strength increases with loading time. Moreover, as the static loading time increases, the more energy absorbed, the more dissipated energy is consumed. © 2022, Editorial Board of Journal of Mining & Safety Engineering. All right reserved.