Theoretical judgement method of overburden “three-zone” based on rock strata deflection deformation and its engineering application

The reasonable determination of the scope of “vertical three zones” (including caving zones + fracture zones + curved subsidence zones) of overlying rock in coal mines is of great significance for gas drainage, coal mining under three conditions and foundation stability evaluation of buildings (structures) in surface subsidence area. It is of great significance to evaluate the stability of the foundation of the material. In this paper, numerical simulation, theoretical analysis, field measurement and other methods are used to study the theoretical discrimination method and engineering application of “vertical three zones” of mining overburden based on the deflection deformation of strata. According to the mining geological conditions of a mine, through the numerical simulation experiment method, the failure and migration law of the mining overburden was systematically analyzed from three aspects: separation, fracture and collapse of mining overburden, and the cavitation zone and fracture zone were obtained. On the basis of the analysis method, the stability condition of the masonry beam and the deflection and bending deformation formula under the critical condition of the broken rock stratum were derived. Based on the above demarcation basis, the "three zones" theory discrimination method and its applicable conditions based on the deflection deformation of the strata were proposed. The method was applied to the theoretical calculation and discrimination of the “three zones” of mining overburden, and was compared with the field observation method of double end water plugging device. The measured results of borehole TV observation method are compared and verified. The research results show that the height of caving zone above the goaf and the development height of water flowing fracture zone, as well as the thickness of the bending subsidence zone were calculated by the proposed theoretical discriminant method. The calculation results are closed to the field measured results, which verifies the rationality and practicability of the proposed "vertical three zones" theoretical discrimination method for mining overburden.