Abstract
Solid backfill coal mining (SBCM) is a green mining technology which can effectively alleviate the environmental problems induced by traditional coal mining techniques, such as surface subsidence, water resources loss, coal gangue occupation, and pollution. In this study, a multilayer Winkler foundation beam model for the overburden key strata is proposed, and the model with two key strata is solved. The subsidence, rotating angle, inner force, and stress of the overburden key strata are systematically analyzed under various backfill elastic modulus, mining height, and soft layer thickness. The results show that the subsidence of the key strata exhibit “basin”-shape curves, and the backfill elastic modulus, mining height, and the thickness of the soft strata have significant influences on the subsidence of the key strata. The shear stress, horizontal stress, and vertical stress of key stratum can be effectively reduced by increasing the backfill elastic modulus. The increase of mining height has little influence on the stress of key stratum that close to the coal seam (key stratum #1), but has a significant effect on the stress of key stratum that above the soft layers (key stratum #2). On the contrary, the effect of increasing soft layer thickness on the stress of key stratum is opposite to that of increasing mining height. In addition, the shear failure of key stratum #1 at mining boundary and the tensile failures on both sides of mining boundary should be preferentially considered in SBCM engineering design. Due to the low shear stress level of key stratum #2, the tensile failure on both sides of the mining boundary should be mainly considered.
Highlights
Solid backfill coal mining (SBCM) is a coal mining technology in which underground coal resources are replaced by backfill [1, 2]
Compared with the traditional underground coal mining technology, the backfill can support the overburden strata in SBCM, which can effectively reduce a series of problems caused by overburden strata deformation and failure, such as surface subsidence [10, 11] and water resources loss [12,13,14,15,16]
According to the solution of the double-layer Winkler foundation beam model, the deformation, stress and inner force of the key strata are systematically analyzed under various elastic modulus Efill, mining height h, soft layer thickness hs, the calculation parameters, and schemes are shown in Tables 1 and 2
Summary
Solid backfill coal mining (SBCM) is a coal mining technology in which underground coal resources are replaced by backfill [1, 2]. Compared with the traditional underground coal mining technology, the backfill can support the overburden strata in SBCM, which can effectively reduce a series of problems caused by overburden strata deformation and failure, such as surface subsidence [10, 11] and water resources loss [12,13,14,15,16]. Miao et al proposed an equivalent mining height theory, which assumes that the actual mining height of SBCM can be equivalent to the deformation of backfill [2] Based on this theory, the Winkler foundation beam model of the upper roof was established, and the analytical solution of the subsidence and internal force of the old roof were obtained. The subsidence, internal forces, stresses distribution, and failure characteristics of key strata are systematically analyzed under various elastic modulus of backfill, mining heights, and thicknesses of soft layers
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