Study on the Law of Surface Subsidence in Layered Mining of Thick Coal Seam with Medium Hard Roof

Abstract

Abstract The thick coal seam carried out by layered mining, the influence range of the overlying rock layer is relatively larger than that of the single-layer mining, and the surface deformation is more intense. At present, the research of thick coal seam mining is mainly concentrated within 15m, and there are relatively few studies on coal seams with a cumulative mining thickness greater than 15m. In order to study the surface sinking law of coal seam mining with a cumulative mining thickness greater than 15m, this paper takes the Mengba as the research object to simulate the change of the surface sinking coefficient after layered mining under the condition that the thickness of the medium hard roof plate and single-layer mining is 5m. In order to verify the correctness of the model, the simulation results are combined with the measured data after the first and second layers of the 1210 working surface of the surface observation station, and the maximum relative error between the simulation results and the measured results was 2.7%, which was less than the specified limit difference of 5%.It shows that the surface sinking coefficient q of stratified mining has the characteristics of segmentation. When the cumulative mining thickness is less than 25m, q is positively correlated with the mining thickness. When the cumulative mining thickness is greater than 25m, the q value will tend to be a fixed value and will no longer change with the increase of mining thickness. Finally, the calculation formula between the ground subsidence coefficient and cumulative mining thickness of layered mining under the condition of medium-hard roof is fitted,which provides a parameter basis for the mining of coal seams in similar mines.