Research on the dynamic development of Bed-Separations under Key Strata and ground subsidence based on large-deflection inclined thin-plate model

Abstract

Abstract Coal mining under the Quaternary thick loose layer makes unique patterns of rock destruction. These patterns directly affect direct and main roof breakage, key strata flexural breakage, Bed-Separations development, ground subsidence, and other studies. In this paper, we developed an approach to solving the deflection of thin plates with additional lateral load and mid-plane force. The dynamic mechanical model of key strata deflection caused by dip coal seams with a thick loose layer is also established. The methods presented are based on the principle of large-deflection of thin-plate, energy method, and fracture mechanics theory. The 7225 work face in Anhui Province, China, was studied. The key strata deflection parameters in the study area were obtained, including 1) the initial and periodic incoming pressure steps of the roof, 2) the height of the caved zone, fractured zone, and continuous bending zone, and 3) the development of height and volume of Bed-Separations. The ground subsidence pattern was revealed as well. The dynamic development of the principal key strata (PKS) calculated by the proposed model is verified with the 3DEC numerical simulation. Meanwhile, 16 Sentinel 1-A images covering the mining period were collected, and the Small Baseline Subset (SBAS) technique was applied to monitor the mining subsidence. It is also cross-validated with the model-calculated subsidence and field measurements. The results showed that the proposed model could contribute to the quantitative analysis of key strata deflection breakage, Bed-Separations development, and ground subsidence caused by excavating inclined coal seams when a thick loose layer covers.