# Research on the Roof Failure Law of Downward Mining of Gently Inclined Coal Seams at Close Range
## 6 Conclusions  
1. Through theoretical calculations, the overburden damage characteristics of the coal seam group during mining were analyzed. After the recovery of the No. 1 coal working face, the height range of the collapse zone is 6.69 to 11.09 m, and the development range of the water-conducting fracture zone is 29.59 to 40.79 m. After the recovery of the No. 2 coal working face, the height range of the collapse zone develops between 24.05 and 33.47 m above the top of the No. 1 coal seam, and the development range of the water-conducting fracture zone is between 74.10 and 94.94 m above the top of the No. 1 coal seam. After the recovery of the No. 4 coal working face, the height range of the collapse zone develops between 30.73 and 40.15 m above the top of the No. 1 coal seam. No. 1 coal seam, and the development range of the water-conducting fracture zone is between 92.26 and 113.10 m above the top of the No. 1 coal seam. The revelation of the synergistic failure mode of the three coal seams provides key scientific support for controlling the overburden stability in the mining of closely spaced, gently inclined coal seams, and is of great significance for guiding safe mining practices in complex coal seams. 2. Numerical simulations were conducted to study the overburden failure patterns during the mining process of the fully mechanized caving face at Yindonggou Coal Mine. The simulation results show that after the mining of the No. 1 coal seam, the collapse zone height is 8.4 m, and the development height of the water-conducting fracture zone extends to 36 m. When the No. 2 coal seam beneath the No. 1 coal seam is mined, the maximum development height of the collapse zone is approximately 27 m above the top of the No. 1 coal seam. The development height of the water-conducting fracture zone extends to 89 m above the top of the No. 1 coal seam. When the No. 1 coal seam and the No. 2 coal seam mining voids are mined beneath the No. 4 coal seam, the maximum development height of the collapse zone is approximately 40 m above the top of the No. 1 coal seam, and the water-conducting fracture zone extends to 112.6 m above the top of the No. 1 coal seam. These results are consistent with the theoretical findings. 3. Based on the on-site measured data analysis, the data for the two zones after the mining of the No. 4 coal seam at Yindonggou Coal Mine are as follows. According to the loss observation and drilling conditions, the water-conducting fracture zone is developed to 110.5 m above the No. 1 coal seam, and the collapse zone is developed to 47.5 m above the No. 1 coal seam. According to the optical imaging logging data, the water-conducting fracture zone is developed to 114.5 m above the No. 1 coal seam, and the collapse zone is developed to 48.1 m above the No. 1 coal seam. These results are generally consistent with the theoretical calculations and numerical simulation results, but there is some deviation. The analysis indicates that the discrepancy is due to the fact that the inter-seam distance used in the theoretical part of the calculations was based on an average value, while the actual inter-seam distance at the drilled location is larger than the average value, leading to a larger result. 4. The results from the combined research methods indicate that the geological conditions at Yindonggou Coal Mine consist of closely spaced, gently inclined coal seams. After the coal seams are mined, the overlying rock layers exhibit significant collapse and fracture development. After the mining of the No. 4 coal seam, the overburden failure forms a multi-seam synergistic failure effect. The collapse zone develops to a height of 48.1 m above the top of the No. 1 coal seam, indicating significant damage to the rock mass in this region. The water-conducting fracture zone develops to a height of 114.5 m above the top of the No. 1 coal seam, suggesting that the fracturedevelopment is widespread and could potentially affect the mining safety of the coal mine. Data curation, J.Z., Y.H., H.L. and D.L. ; methodology, T.Y.