Abstract:
The movement, deformation, fracture, and stress changes of overlying strata caused by coal mining are the main reasons for the weighting on the longwall face and surface ecological damage. Studying the movement laws and damage mechanisms of overlying strata during mining is the core issue in solving underground safety production, aquifer protection, surface construction facilities, and ecological protection. It is the theoretical basis for achieving green and safe mining in coal mines. To fully understand the conduction mechanism of mining damage, taking the overburden "arch shell" structure as the core, the current research results of overburden movement are systematically reviewed. According to the difference of overburden combination and medium characteristics, the arch in mining field are divided into loose layer arch and bedrock arch. Bedrock arches can be further divided into fracture arches and stress arches. On this basis, the research progress and existing problems of bedrock arch are discussed according to the arch shell evolution mechanism and research methods: The theoretical model can give the arch trace equation and judge the bearing characteristics of the arch. However, there are some problems, such as simplification of boundary stress conditions, assumption of rock stratum homogeneity, assumption of arch trace and calculation of arch thickness. Numerical simulation can well give the location, thickness and evolution characteristics of arch shell. However, the stress arch shell simulated by finite element ignores the influence of rock fracture, while the stress or fracture arch shell simulated by discrete element depends on the division of blocks. Similar simulation can only qualitatively observe the development characteristics of fracture arch, and it is difficult to determine the range of stress arch. The existing applications based on overlying rock arch shells focus on predicting and preventing longwall face weighting and surface subsidence through arch shell evolution models. However, there are relatively few methods for actively regulating overlying rock arch shells. Based on this, this paper summarizes three methods for regulating overlying rock arch shells: source preset arch shell method, process control arch shell method, final stability control arch shell method. Finally, based on the existing achievements, a theoretical calculation model and simulation method for mining damage arch shell theory based on the law of energy conservation were further proposed. It provided the theoretical support and research methods for the evolution characteristics of the overlying rock fracture structure stability in the longwall face and the treatment of surface subsidence.