# Research on the Laws of Overlying Rock Fracture and Energy Release under Different Mining Speeds
## 2 Influence of Working Face Advancing Speed on Energy Release of Overlying Strata
### Analysis of Displacement Deformation of Overburden Rock under Different Mining Speed
During the low-speed mining process, the low rock strata above the coal seam change concurrently with the continuous mining of the working face, and the roof subsidence closely mirrors the mining height of the coal seam, as shown in Figure 10. The middle rock layer, however, has fewer monitoring points and exhibits a smaller numerical change compared to the low rock layer. In the case of the high rock strata, the number of monitoring points is reduced. The rock strata below them are fractured and expanded, resulting in minimal changes in the subsidence of the rock strata. Comparing and analyzing the displacement changes at monitoring points during coal seam excavation at different mining speeds, as well as the deformation after the overburdened rock stabilizes at the end of mining, reveals distinct patterns. The vertical displacement changes in monitoring point 5 in the low-level rock layer were selected for analysis, as shown in Figure 11a. The initial caving step of the roof varies under different mining speeds. In low-speed mining, the roof began to show signs of sinking when excavated to 50 cm and broke when mined to 60 cm. While in rapid mining, the roof does not begin to sink until it reaches 80 cm and breaks at 90 cm. In the meantime, the impact range of roof subsidence during rapid mining is significantly larger than that of slow mining, and after the roof fractures and stabilizes, the separation amount between the low and medium rock layers during rapid mining is 5.2 cm, while the separation amount during slow mining is 2.1 cm. After the coal seam mining is completed and stabilized, the overlying rock morphology of the goal varies at different mining speeds, as shown in Figure 11b. In rapid mining, the fragmentation of the overlying rock blocks results in a large block size, significant overall subsidence and, ultimately, a large separation space. When mining at a slow speed, the block size formed by the overlying rock is relatively small, and it is broken into blocks with little room for separation. This phenomenon can  
Figure 10: The figure shows the vertical displacement changes in the rock stratum under low-speed mining conditions. be attributed to the disruption of the stress balance of the roof during rapid mining of the working face. The deformation of the overlying strata is not adjusted in time, leading to an increase in the initial collapse step. Ultimately, the upper strata cannot bear the weight of the rock layers, leading to an overall collapse. This total collapse of the overlying rock means the deformation of the surrounding rock is not fully expanded, resulting in a large block of the collapsed rock mass and extensive separation of the roof of the high rock layer. The digital speckle simulation analysis of the movement law of rock strata under different working face mining speeds reveals that as the mining speed increases, so too do the overburden caving speed, fracture block degree, and amount of roof separation. This observation confirms the assertion that the fracture distance of the stop increases in conjunction with the rise in mining speed. Figure 5:0 The figure shows a comparison of overlying strata movement changes under different mining speeds.