## 1 Introduction  
The excavation and unloading of a roadway will invariably produce stress concentration in the surrounding rock in the deep high-stress environment. With increasing stress, the stress state of the rock surrounding a tunnel surpasses the ultimate bearing capacity of the rock body, resulting in fracture. The stress condition of the radial depth of the rock surrounding the roadway is close to, but not more than, the ultimate strength of the rock body to cause damage, and this portion of the unloading damage surrounding the rock body becomes the roadway's major bearing structure. As a result, it is critical to investigate the re-bearing capability and damage mechanism of rock masses injured by peak front unloading [1; 2]. To give full play to the strengthening effect of supporting structures, and to ensure the safe exploitation and utilization of underground coal resources and space, the mechanical properties of unloaded rock masses have received increasing attention [3; 4; 5; 6; 7]. [PERSON] et al. [8] found that the expansion spring back phenomenon occurs when a rock mass is unloaded on one side. [PERSON] et al. [9] discovered that the interaction between cracks during confining pressure unloading is more sensitive than that during axial pressure unloading, and that crack weakening during confining pressure unloading plays a leading role in the deformation of the surrounding rock. [PERSON] et al. [10] studied the influence of intermediate principal stress on rock strength and failure mode under true triaxial unloading conditions by unloading the minimum principal stress. [PERSON] et al. [11] analyzed the hysteresis effect of the rock stress--strain curve through cyclic loading and unloading tests under different confining pressures. [PERSON] et al. [12] examined the strain rate effect of the impact compression strength of red sandstone via impact compression testing through red sandstone under the unloading condition of confining pressure. In a study by [PERSON] et al. [13], based on the generalized Hooke's law, a method for determining Poisson's ratio of rock samples was found through changing axial stress and unloading lateral stress testing. Acoustic emission (AE) is an elastic wave generated by the initiation and expansion of cracks in rock. Acoustic emissions generated by different fracture forms in unloaded rock have different characteristics. Therefore, the changes in crack growth forms in unloaded rock can be studied according to the acoustic emission characteristics. [PERSON] et al. [14] simulated rock mass excavation under high-stress conditions and found that there was instantaneous rebound when the minimum principal stress was unloaded, and the acoustic emission ringing times increased significantly with the increase in the second principal stress. [PERSON] et al. [15] used the hierarchical clustering method to divide AE events into tensile failure and shear failure, and studied the effects of unloading rate, confining pressure, and unloading time on the tension--shear ratio (the ratio of tensile failure to shear failure). [PERSON] et al. [16] studied the evolution characteristics of AE in the process of brittle rock failure under complex stress paths and found that the AE count rate of unloading failure was much higher than that of loading failure. [PERSON] et al. [17] believed that the simultaneous occurrence of UHF, HF, MF, and LF in the AE power spectrum could be used as the basis for judging rock unloading tests. Under the action of excavation and unloading, roadway surrounding rock masses at a certain depth range have varying degrees of unloading damage. In the process of en-gineering operations, this part of the unloading-damaged rock mass will bear various loads for lengthy periods, and the reloading mechanical properties of the un-loading-damaged rock mass will directly affect the stability and safety of engineering rock masses [18].