The whole-cycle dynamic evolution characteristics of overburden fracture and movement in extremely high mining longwall face in western mining area

In order to explore the structural characteristics and movement laws of overburden damage and fracture in the extremely high mining longwall face in the western mining area, the 8.8 m extremely high mining longwall face of Shangwan Coal Mine was used as the research background. Based on the field measurement results, physical modeling and other methods, the geological characteristics of medium burial depth, thick bedrock and inherent mining damage conditions of overlying rock damage and its spatiotemporal evolution process were studied. The results show that: the damage height of overlying rock shows a "stepwise" development and evolution process. It reveals the "three-zone" fracture mode of overlying rock in extremely high mining longwall face under special geological conditions and the restraining effect of the combination of thick and soft rock layers above the primary key strata on mining damage. The main roof collapsed in the goaf in the form of a "caved rock block", while the primary key strata formed a "masonry beam" structure. The "non-uniform" characteristics of overlying rock subsidence were formed in the form of "collaborative subsidence groups" when the overlying rock broke and settled. The subsidence of overlying rock showed the non-linear decrease with the decrease of burial depth, and the surface movement was uniform with the bending of thick and soft rock layers, with the subsidence coefficient of 0.58.