## 1 Introduction  
In underground engineering, the stress state of rock mass is usually very complicated under the joint action of geological conditions and mining. To facilitate the analysis and research, the stress state of rock mass is usually simplified and can be understood as a three-dimensional compression state. Due to roadway excavation, the load of surrounding rock is relieved in a certain direction, which makes the original equilibrium state suddenly unstable. To rebalance the stress, the stress will transfer to the depth of the surrounding rock. This transfer process is inevitably accompanied by energy transformation, which leads to the deformation and failure of the surrounding rock. In essence, the deformation and failure of surrounding rock result in the loading and unloading of rock mass caused by unloading. After unloading, the stress in a certain direction of the surrounding rock increases, forming the loading condition, or decreases, forming the unloading condition. Thus, the ultimate bearing capacity of the surrounding rock is limited. Loading will lead to stress exceeding the ultimate bearing capacity, while unloading will reduce the capacity. Under the action of these two aspects, rock mass deformation and failure will occur. Stressredistribution and strain energy accumulation make the gathered energy of surrounding rock easily released along the working face, resulting in surrounding rock damage, cracking, and even sudden instability of surrounding rock [1; 2; 3]. The surrounding rock mass always exchanges energy with the outside world during deformation, damage, and failure [4]. Therefore, how to consider the mechanical properties and energy evolution characteristics of unloading rock mass is the focus of rock deformation and failure mechanism research. For rock deformation analysis and energy evolution, scholars have carried out rock loading test studies under different test conditions and obtained fruitful results. [PERSON] et al. [5] analyzed the influence of cavities and cross-joints on the energy characteristics of rock samples and the energy evolution law by carrying out uniaxial loading tests and combining them with the rock energy theory. [PERSON] et al. [6] discussed the size effects of energy accumulation and dissipation in sandstone through a uniaxial compression test, and revealed that the elastic energy evolution of sandstone with different aspect ratios follows the law of linear energy storage. [PERSON] et al. [7] carried out uniaxial tests on sandstone with different water content and analyzed the relationship between energy dissipation and the number of cracks in the loading process. [PERSON] et al. [8] analyzed the law of characteristic energy in the loading process by carrying out a uniaxial cyclic loading test of sandstone. [PERSON] et al. [9] carried out triaxial tests on three kinds of rocks to study energy characteristics such as energy dissipation and energy storage limit during rock deformation. [PERSON] et al. [10] analyzed the relationship between wave velocity and energy dissipation in the red sandstone deformation and failure process based on the full stress-strain curve by carrying out triaxial loading tests. [PERSON] et al. [11] obtained the transformation law of axial elastic energy and dissipated energy by conducting rock mechanics tests under different stress paths. [PERSON] et al. [12] carried out rock mechanics tests with different loading modes and analyzed the rock deformation and failure mechanism and post-peak energy evolution characteristics. [PERSON] et al. [13] revealed the relationship between energy rebound density and stress by carrying out rock mechanics tests at different loading rates, and then analyzed the microscopic mechanism of energy characteristics. [PERSON] et al. [14] combined with digital image correlation technology and acoustic emission technology, and then conducted direct shear tests on different rough joints to analyze the deformation energy evolution law. [PERSON] et al.