Abstract: The main cause of underground disasters in coal mines is the stress concentration and high-intensity unloading of surrounding rock caused by man-made mining and the extraction of coal resources. Especially when the surrounding rock is affected by confined water, it is easy to lose stability and damage, which leads to the occurrence of disasters. Accordingly, the experimental study on the mechanical properties and energy evolution law of sandstone under the coupling of seepage and mining stress was carried out by means of Rock Top multi-field coupling tester. The test results show that : (1) The total stress-strain curve of sandstone can be divided into five stages. After the sandstone begins to unload, it changes from axial deformation to circumferential deformation. (2) The peak stress of sandstone increases with the increase of unloading level. With the increase of osmotic pressure difference, the peak stress of sandstone is not obvious due to the superposition of surrounding rock and water pressure. (3) The higher the unloading level of sandstone is, the larger the axial strain value at the peak stress is, and the axial deformation of sandstone is more obvious under high unloading level. The evolution law of dilatancy angle curve of sandstone roughly follows the law of ' increase—ecrease—increase—decrease ', and the expansion behavior of sandstone is more significant under low unloading level. (4) With the increase of initial unloading level, the elastic strain energy density of sandstone increases as a whole. The energy distribution coefficient of elastic strain energy density increases first and then decreases with the increase of axial strain of rock sample. (5) The instantaneous energy distribution coefficient of elastic strain energy of sandstone presents the change rule of 'increase—decrease—increase 'with the increase of axial strain of rock sample. The energy storage capacity of sandstone elastic strain energy reaches its peak after entering the elastic deformation stage, and its energy release capacity reaches its peak before entering the residual stress stage.

Key words: hydro-mechanical coupling, mechanical properties, deep surrounding rock, energy evolution, energy storage capacity