## 5 Conclusions  
In this paper, the effects of the roadway height-width ratio and lateral pressure coefficient on the plastic damage zones, horizontal displacements, and stress changes in the roadway sidewalls were investigated. The purpose was to study the brittle damage mechanisms of highly stressed roadway sidewalls. The following conclusions were drawn.  
1. The rock surrounding the roadway of the Datai coal mine is under high in-situ stress, and the diabase is dense and brittle. The roadway sidewall damage mostly occurs in the upper middle or middle-lower part, mainly as shear failures, forming a large falling block fissure with a wide range, and finally forming a V-shaped failure zone.
2. When the height-width ratio of the roadway increases from 0.25 to 2.00, the tensile and shear plastic zones of the roadway sidewall gradually expand. The tensile plasticity damage zone is V-shaped, and the shear plasticity damage zone is circular. In addition, the shear plastic damage zone is larger than the tensile plastic damage zone. The vertical stress in the roadway sidewall experiences two peaks. The stress decreased slightly between the peaks, and then gradually decreased and stabilized. It was found that the horizontal displacement of the roadway sidewall increased linearly. With the rise of the roadway height-width ratio \(h/w\), the values of the two peaks get closer and closer. The stress at the two stress concentration points increases and then decreases, and the stress concentration location is gradually shifted to a deeper part of the roadway sidewall.
3. As the \(\lambda\) value increases from 0.1 to 1.0, the tensile plastic damage area of the roadway sidewall first decreases and then remains unchanged, and the shear plastic damage zone first increases and then decreases. The horizontal displacement of the roadway sidewall shows a trend of decreasing and then increasing. The vertical stress within the roadway sidewall increases at the first peak point, then decreases slightly, and then continues to increase to the second peak point. The stress value decreases linearly at the first stress concentration point and tends to increase and then decrease at the second stress concentration point. Then it gradually decreases and stabilizes. The stress value decreases linearly at the first stress concentration point and tends to increase and then decrease at the second stress concentration point. It is worth noting that these two stress concentration locations are shifted to the boundary of the roadway sidewall.  
Conceptualization, X.W. and Y.Z.; methodology, Y.Z.; software, M.X.; validation, J.F.; formal analysis, B.J.; investigation, J.F.; writing--original draft preparation, X.W. and B.J.; writing--review & editing, Y.Z.; supervision, Y.Z. and M.X. All authors have read and agreed to the published version of the manuscript.  
Figure 18: Relationship between \(\lambda\) and maximum vertical stress inside of the roadway sidewall: (**a**) First stress peak point inside of roadway sidewall; (**b**) Second stress peak point inside of sidewall.  
**Funding:** This research was funded by National Natural Science Foundation of China (No. 52104137), Major Program of Shandong Provincial Natural Science Foundation (No. ZR2019 ZD13) and Shandong Provincial Natural Science Foundation (No. ZR2020 QE122).  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** The data of this work can be shared to the readers depending on the request.  
**Conflicts of Interest:** The authors declare no conflicts of interest.