## 3 Result
### Dynamic Response Characteristics of Disturbed Surrounding Rock under Impact Load
#### 3.2.2 Dynamic Response Characteristics of Disturbed Surrounding Rock under Impact Dynamic Load  
Many field engineering cases show that the disturbance induced by mining in the opposite direction is an impact phenomenon with typical dynamic failure characteristics. To capture the dynamic response characteristics of disturbed surrounding rock under the impact dynamic load, four measuring points are arranged on the surface of the model, representing the near driving face, the inside of the central coal pillar disturbed by mining in the opposite direction, the near stopping face, and the overlying high roof area. The particle motion acceleration velocity and displacement parameters of roadway surrounding rock under impact dynamic load are monitored. The acceleration dynamic response characteristics of coal and rock mass at measurement points in different regions are shown in Figure 5b-h.  
Figure 5: Dynamic response characteristics of disturbed surrounding rock under impact dynamic load: (**a**) measuring points; (**b**) 0.1 m; (**c**) 0.3 m; (**d**) 0.5 m; (**e**) 0.7 m; (**f**) 0.9 m; (**g**) 1.1 m; (**h**) 1.3 m.  
As can be seen from the figure, the acceleration response characteristics of measurement points in different regions show a relatively consistent rule under the impact dynamic load: after the impact dynamic load, the peak acceleration decreases exponentially, with a short duration and fast signal attenuation, which is similar to the phenomenon of \"one main shock-multiple aftershocks\" of an earthquake, indicating that the impact dynamic load can induce the dynamic fracture of the disturbed coal rock mass. Taking Figure 5b as an example, when the pendulum height is 0.1 m and the corresponding input dynamic load size is 3.27 \(\times\) 10\({}^{5}\) J, the peak acceleration of the 1# sensor closest to the focal point is the largest, which is 4.37 m/s\({}^{2}\). The peak acceleration of the distant 2# sensor is 2.57 m/s\({}^{2}\). The peak acceleration of the 3# sensor located around the stope face is 0.87 m/s\({}^{2}\). The peak acceleration of the 4# sensor farthest from the source is 1.39 m/s\({}^{2}\). It is shown that the dynamic response intensity of each region of the model is not only affected by the distance of vibration wave propagation but also related to the spatial location of mining disturbance, which can be mainly reflected as the following: (1) After the pendulum falls, the left side of the model is directly disturbed by the dynamic load of the impact. The dynamic load energy directly acts on the left side of the heading face. The acceleration duration is short and the attenuation is relatively fast. (2) Measuring point 2# is located at the back wave side. After the incident vibration wave, it first passes through the free space of the heading face and acts on the point after transmission and reflection on the roadway surface many times. Its energy attenuates slightly, so the acceleration of measuring point 2# is slightly lower than that of measuring point 1#. (3) The measuring point No. 3 is located in the advanced position of the working face. Because it is in the plastic zone of surrounding rock affected by mining, the coal rock mass is relatively broken, so the ability to absorb incident waves is greatly reduced, and its peak acceleration is the minimum. (4) Measuring point No. 4 is located on the top roof of the key layer above the stope working face. Although it is the furthest away from the source and its energy is low after attenuation, its peak acceleration is higher than measuring point No. 3 because the key rock layer is relatively dense and no significant rupture occurs. Therefore, the response rules of peak acceleration in different regions are as follows: driving face > central coal pillar > upper strata of stopping face > near the stopping face.