Study on surface movement characteristics of repeated mining under thick alluvium

In order to study the influence of multi-seam repeated mining under thick alluvium on surface movement, the surface movement characteristics of Guqiao coal mine repeated mining were analyzed based on the geological and mining conditions of Huainan coal mining area. Then FLAC^3D numerical simulation model of multi-seam repeated mining under thick alluvium was built, and the surface deformation characteristics and the relationship between the number of parameters and mining times were analyzed. Research results showed that when the first mining under thick alluvium surface subsidence factor is greater than 1, the alluvium is gradually compacted. The surface subsidence coefficient presents the tendency of linear increase with the mining times, but the mining subsidence coefficient tends to be stable when the mining time reaches three as the alluvium has been compacted gradually. When the goaf reaches the supercritical size, the boundary of subsidence basin is no longer increased, but is affected by the mining depth. The tangent of main effect angle and the limit angle have linear increase relationship with mining times. The results provide theoretical basis and technical reference for studying the surface movement characteristics under thick alluvium.