## 3 Damage Mechanisms of the Roadway's Surrounding Rock under Dynamic Pressure
### Distribution Shape and Evolution of Plastic Zones  
According to the boundary equation of the plastic zone of the rock surrounding the roadway under dynamic pressure, the shape of the plastic zone is related to the dynamic pressure coefficient, original rock stress, lateral pressure coefficient, roadway radius, internal friction angle, cohesion, and other factors. When the size of the roadway under dynamic pressure and the mechanical properties of the surrounding rock remain unchanged, the size and boundary of the plastic zone depend on the size of the dynamic pressure coefficient. Hence, an analysis was conducted on roadways with varying coefficients of lateral pressure to investigate the impact of vertical and horizontal mining activities on the boundary of the plastic zone of surrounding rock. When the roadway is located below the mining working face, the roadway will be affected by vertical mining. Taking three common lateral pressure coefficients \(\lambda\) = 0.8, \(\lambda\) = 1.0, and \(\lambda\) = 1.5 as examples, Figure 5 shows the distribution of the plastic zone of the surrounding rock under the influence of vertical dynamic pressure. Figure 5a shows the plastic zone of the roadway's surrounding rock when \(\lambda\) is 0.8. When \(K_{1}\) is 1.0, the shape of the plastic zone of the surrounding rock is elliptical, and the roadway is under the action of static load and is not affected by dynamic pressure. The plastic zones at the sides of the roadway are larger, and the plastic zones of the roof and floor are smaller. When \(K_{1}\) increases to 1.5, the plastic zone expands from the upper part to the deep part of the surrounding rock, and the zone becomes roughly butterfly shaped. As \(K_{1}\) further increases, the plastic zone gradually expands in the four directions of the top and bottom corners of the roadway, and the butterfly shape becomes more obvious. Figure 5b shows the plastic zone of the roadway's surrounding rock when \(\lambda\) is 1.0. When \(K_{1}\) is 1.0, the shape of the plastic zone of the roadway under static load is circular. As \(K_{1}\) increases, the shape evolution pattern is similar to that in Figure 5a, and the distribution shape evolves from circular to butterfly. However, the influence of \(K_{1}\) is relatively weakened. As shown in Figure 5c, when \(K_{1}\) is 1.0, the shape of the plastic zone of the roadway under static load is elliptical, and the shape of the plastic zone changes from an ellipse to a rounded rectangle as \(K_{1}\) increases. The plastic zones at the sides of the roadway gradually increase, while the plastic zones at the roof and floor weaken slightly. As \(\lambda\) increases, the influence of \(K_{1}\) on the distribution shape and range of the plastic zone gradually weakens. When the roadway and the mining face are in the same coal seam, the rock surrounding the roadway will be affected by horizontal mining. The corresponding plastic zone of the surrounding rock is shown in Figure 6. Figure 6a shows the distribution shape of the plastic zone when \(\lambda\) is 0.8. As \(K_{2}\) increases, the shape of the plastic zone changes from elliptical to butterfly. The scope of the plastic zone gradually increases and extends toward the roof  
Figure 5: Distribution of the plastic zone subjected to vertical dynamic pressure. and floor of the roadway, while the plastic zones at both sides of the roadway gradually weaken. When \(\lambda\) is 1.0 or 1.5, the plastic zone of the roadway's surrounding rock is as shown in Figure 6b,c. As \(K_{2}\) increases, the radius of the plastic zone increases significantly, gradually extending to the four corners of the roadway's surrounding rock, and the butterfly shape becomes more obvious. As \(\lambda\) increases, the influence of \(K_{2}\) on the distribution shape and range of the plastic zone becomes increasingly obvious.