## 1 Introduction  
In underground coal mining, heavy equipment such as hydraulic supports are retraced to the next working face after mining has been completed in a comprehensive working face, and the speed of the retracement is a significant factor in the efficiency of coal production [1]. Pre-excavation technology for double retracement channels arranges two channels parallel to the working face in advance near the stopping line, which allows quick retracement of the equipment through the auxiliary retracement channel (ARC) after the working face has been cut through the main retracement channel (MRC). The stability of the retracement channel surrounding rock is crucial for the safe and efficient retracement of the equipment and to guarantee the continuity of the retracement work [2]. The spacing of two retracement channels is the key factor in controlling the stability of the ARC surrounding rock. Therefore, it is beneficial in practical engineering to improve the understanding of the stress environment of the ARC under different spacings, clarify the surrounding rock deformation damage mechanism, and propose a reasonable spacing setting method. The retracement channel is strongly influenced by mining; the surrounding rock can be seriously deformed and cause disasters, such as roof falling and coal wall spalling, at the end of the mining period [3; 4; 5]. It has been determined that the stress concentration from exploitation is the main reason for roadway destruction [6; 7; 8]. Field measurements, numerical simulations, and other means have revealed that the horizontal and vertical stresses rapidly increased after mining, and the stress environment was complex at the working face [9; 10; 11]. Using elastic-plastic theory, the appearance of different plastic zone shapes and the expansion laws of the roadway surrounding rock in the nonuniform stress field were analyzed, which proposed that the plastic zones in the roadway surrounding rock were butterfly-shaped, elliptical, and circular [12; 13]. The mechanism of the analyzed damage to the roadway surrounding rock indicated that different surrounding rock plastic zone shapes would contribute to different degrees of deformation in the roadway [14; 15]. These research results have shown the morphological variability and mechanistic complexity of the damage and deformation to roadway surrounding rock. However, the stress conditions, where the pre-excavation of the two retracement channels is located, are more complex due to the specificity of being arranged in advance and the influence from continuous mining [16; 17]. Therefore, many scholars currently focus on controlling the stability of the retracement channel. The stress vector distribution in the retracement channel region is obtained through numerical simulation and field investigation [18]. [PERSON] [19] discovered the stress transfer phenomenon in the coal pillars on two sides of the retracement channel during the end of the mining period. [PERSON] et al. [20] proposed that the load on the upper coal pillars and mining disturbances caused plastic zone stress asymmetries in the retracement channel. [PERSON] and [PERSON] [21] presented a stress release and roof cutting method to control the retracement channel stability. [PERSON] [22] investigated the mechanism of the coal pillar load transfer from the working face to the MRC, with a method to determine the [PERSON] of the coal pillars. Nevertheless, there are few studies on the stressful environment and surrounding rock deformation damage in the ARC during mining, which makes it more challenging to control the surrounding rock stability in the ARC.