Study on the Failure Law of Overlying Strata in Thick Coal Seam Mining under the Condition of Shallow Burial Depth, Thick Loose Layers, and Thin Bedrock

In order to study the failure characteristics of overlying strata during the mining of thick coal seams under the conditions of shallow burial depth, thick loose layers, and thin bedrock, this study was based on the geological conditions of the 13101 working face in the Shaping Coal Mine. By comprehensively applying methods such as theoretical analysis, numerical simulation, and on-site measurement, a study is conducted on the overlying strata failure law during the working face mining process. The results show that: (1)-Through the observation of flushing fluid loss, the development height of the water-conducting fracture zone in the working face is 88.6-92.2 m, with a fracture-mining ratio of 7.9-8.2; the results of numerical simulation and theoretical calculation are both relatively close to the measured results. (2) With the mining of the working face, the surface movement and subsidence trend evolves from a ″V″ shape to a ″U″ shape. Affected by the liquidity index of the thick loose layers, the surface subsidence lags behind the upward development process of the overburden failure height; (3) There is a Boltzmann functional relationship between the overburden failure height and the mining distance, and its evolution can be divided into four stages: initiation, rapid increase, slow increase, and stability. The first three stages mainly occur in the thin bedrock, while the stability stage appears in the thick losse layers; (4) The failure of overlying strata exhibits a "two-belt" destruction pattern, in which the thin bedrock acts as a support, while the thick loose layer mainly provides high static load and has an inhibitory effect on the degree of overburden destruction.