## 1 Introduction  
After excavation, the stress state of the surrounding rock changes dramatically and stress is redistributed [1; 2; 3], which can lead to the instability of a roadway. Common failure modes for the surrounding rock include brittle failure, roof collapse, sidewall collapse [4; 5; 6], etc. The deep roadway is subjected to high stress, requiring excavation to confront complex stress conditions. The rock behaves in a completely different mechanical manner compared to shallow rock. Its strength characteristics, deformation mechanism, and damage mode are difficult to explain accurately using traditional theories [7; 8]. How to effectively evaluate and maintain the safety of the surrounding rock has been a hot issue in the research of underground rock support engineering. The surrounding rock consists of the roof, floor, and sidewalls, and the stability of each component is of utmost importance. A prevalent method for examining the stability of a roadway is numerical simulation. The numerical simulation method can simulate complicated underground structures and geological conditions. This capability supports the investigation of parameter sensitivity and aids engineers in optimizing design schemes for underground engineering. The stress and strain in the surrounding rock after excavation are analyzed to determine the damage state of the roadway [9; 10; 11; 12]. Most studies focus on the failure of roof rock and floor rock, while disregarding the significant contribution of the sidewall rock in maintaining the stability of a roadway. When damage occurs in the sidewall, it also means that the span of the roadway will increase. Although the range of sidewall damage is limited, it should be noted that this limited damage range will trigger the overall failure of the roadway. As concluded by some scholars [13; 14; 15], it can result in a roof collapse or floor heave with the gradually increasing width of an underground excavation, which leads to the overall instability of the roadway. [PERSON] et al. [16] proposed a numerical method to study the floor heave of roadways under dry and soaking conditions, and the obtained results were in good agreement with field measurement data. [PERSON] et al. [17] studied the influence of ground stress and rock layers on the safety of the surrounding rock and found that a weak roof rock layer is the main factor affecting the stability of a roadway. The failure types in sidewall rock include spalling, bursting, and folding [18; 19]. [PERSON] et al. [20] proposed that damage to sidewalls primarily results from tensile stress, which progressively transitions to shear damage as one moves toward the interior of a rock mass. [PERSON] [21] analyzed some primary mechanical damage mechanisms of roadway sidewalls, categorizing the forms of roadway sidewall failure as compression-shear, gravity-slip, splitting, and transverse-arch. [PERSON] et al. [22] simulated the stress of rock around coal roadways using a PFC two-dimensional numerical method. [PERSON] and [PERSON] [23] suggested that rock failure begins at the corners of the bottom, progressively extending toward the bottom and sidewalls, ultimately leading to uncontrolled floor heaving in the roadway. With the transfer of concentrated stresses in the sidewalls to greater depths, the roof and floor are relatively stable and the sidewalls are gradually destroyed [24]. The plastic zone of surrounding rock near the sidewall is larger than that near the roof [25]. The serious damage of a roadway sidewall demonstrates that it is the key part that needs to be supported [26; 27; 28; 29]. Local damage to the sidewall rocks can cause instability in the entire roadway, resulting in significant economic losses and even casualties. Therefore, it is important to avoid such damage to ensure the safe construction and use of deep underground coal mine roadway projects. Studying the deformation and damage mechanisms of sidewall rock is crucial to ensuring the safety of the surrounding rock in deep underground coal mining roadways.