**5. Conclusions**

In this paper, the deformation volume and deformation characteristics of the return airway of 30503 in Tashan mine were analyzed. We conducted short-term surface displacement monitoring by using field testing and determined the existence of the asymmetric damage morphology of the roadway and established a roadway layout optimization model by means of numerical simulations for the actual engineering situation of the working face. We also analyzed the main stress magnitude and the plastic zone morphology of the roadway for eight groups at different positions. The study showed the following.

(1) Via surface displacement observations, it can be seen that the 30503 working face return roadway experienced large deformations within a short period of time, and the two gangs' displacement is obviously larger than the top plate's displacement. At the same measurement point position, the two gangs' displacement and the top plate's displacement also has obvious differences. The roadway exhibits obvious non-uniform damage phenomena.

(2) The residual coal pillar of the overlying coal seam affects the stress environment of the lower coal seam roadway due to the stress from its own weight. The change in the roadway's layout position has little effect on the trend of the main stress curve of the lower coal seam, and the peaks of σ<sup>1</sup> and σ<sup>3</sup> in the horizontal direction appear at the residual coal pillar. σ<sup>1</sup> and σ<sup>3</sup> and σ1/σ<sup>3</sup> are smaller at the position far from the residual coal pillar.

(3) As the coal mine is mined by releasing the top coal, the arrangement of the roadway in the vertical direction should be in the middle and lower positions of the coal seam. Although the distribution of the plastic zone along the bottom of the roadway is small, its roadway's deformation variable is larger. In order to guarantee the stability of the roadway, the roadway should be arranged in the middle position of the coal seam.

(4) When the coal column left in the lower coal seam's roadway is 4 m, the maximum deformation of the roadway's surrounding rock is the smallest. At this time, the roadway is farthest away from the residual coal column of the overlying coal seam and is least affected by its stress; therefore, during the mining process of the coal seam group, the roadway is arranged as a small coal column (far away from the residual coal column), which can effectively improve the stability of the roadway.

**Author Contributions:** Conceptualization, X.-H.W., H.-H.Z. and R.-Q.G.; methodology, X.-H.W. and Z.W.; software, Z.W. and X.-L.L.; validation, R.-Q.G. and Y.S.; formal analysis, H.-H.Z. and Y.S.; investigation, X.-H.W. and R.-Q.G.; resources, X.-H.W. and Z.W.; data curation, Z.W. and X.-L.L.; writing—original draft preparation, X.-H.W. and R.-Q.G.; writing—review and editing, H.-H.Z. and Y.S.; visualization, X.-L.L. and Y.S.; supervision, Z.W.; project administration, X.-H.W. and Z.W.; funding acquisition, X.-H.W. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by the Natural Science Foundation of China (U22A20165), grant number "51574224", and the Guizhou Province Science and Technology Support Plan Project of China, grant number "Guizhou Province Science and Technology Support Plan Project [2021] General 400".

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** The data presented in this study are available upon request from the corresponding author.

**Conflicts of Interest:** The authors declare no conflict of interest.
