Laboratory of Mining Response and Disaster Prevention and Control in Deep Coal Mines, Anhui University of Science and Technology
School of Safety Science and Engineering, Anhui University of Science and Technology
School of Earth Sciencesand Geomatics Engineering, China University of Mining and Technology-Beijing

In the process of underground excavation, the surrounding rock is in a very complex stress environment, especiallyunder the influence of its anisotropy, the occurrence of dynamic disaster is hidden. In this paper, the loading and unloadingtests of sandstone in different principal stress directions were carried out by using the true triaxial unloading disturbedrock test system. The mechanical properties and failure characteristics of true triaxial under different principalstresses were studied, the energy evolution mechanism in other directions induced by loading and unloading of different principal stresses was analyzed. Results showed that under the influence of rock mass secondary stress anisotropy, duringthe cyclic loading and unloading process of the first principal stress, the strain in other directions shows opposite deformation.The volumetric strain compresses first and then expands, and the final volumetric strain shows a macroscopic phenomenonof expansion. When the third principal stress of high confining pressure rock mass is unloaded, the first principalstress produces a compression deformation, while the second and third principal stresses produce an expansion deformation.The deformation of the second principal stress is less than that of the third principal stress, and the deformation in unloadingdirection changes from linear elastic state to elastic-plastic nonlinear state. The accumulated energy of rock massis a great difference between the first principal stress unloading and the third principal stress unloading. The energy variationcharacteristics of unloading in the dominant direction determine the energy accumulation and release law in the othertwo induced directions. The limit stored energy of the third principal stress unloading rock decreases, and the secondprincipal stress accelerates the rock failure with the increase of the first principal stress, which verifies that the rock is easierto be destroyed by unloading than by loading. The higher the unloading rate of the third principal stress, the higher theenergy released and the lower the dissipated energy, and the lower the energy density and total accumulated energy densityin the unloading direction of rock mass. The main cause of dynamic accidents is the accumulation and release of energyin rock mass. The secondary anisotropy of rock mass has a great influence on the ultimate stored energy of rock mass.The study on the influence characteristics of three-dimensional loading and unloading secondary stress on the ultimatestored energy of rock mass provides a reference for preventing rock burst.

国家自然科学基金资助项目(52004006，51974009)；安徽省科技重大专项、安徽省“省特支计划”的领军人才资助项目(T000508)

许文松，赵光明，孟祥瑞，等. 真三轴加卸载岩体各向异性及能量演化机制[J]. 煤炭学报，2023，48(4)：1502−1515

XU Wensong，ZHAO Guangming，MENG Xiangrui，et al. Anisotropy and energy evolution mechanism of rock mass under true triaxial loading-unloading[J]. Journal of China Coal Society，2023，48(4)：1502−1515