Abstract
In fully mechanized caving mining of extra-thick coal seams, the movement range of overburden is wide, resulting in the breakage of multilayer hard roofs in overlying large spaces. However, the characteristics, morphology and impact effect of hard roofs at different levels are different and unclear. In this study, a secondary development was used in the numerical simulation software ABAQUS, and the caving of rock strata in the finite-element software was realized. The bearing stress distribution, fracturing morphology and impact energy characteristics of hard roofs at different levels were studied to reflect the action and difference of hard roof failure on the working face; thus, revealing the mechanism of the strong ground pressure in stopes, and providing a theoretical basis for the safe and efficient mining of extra-thick coal seams with hard roofs.
Highlights
Thick and extra-thick coal seams are the primary coal seams of high-efficiency mining, for which the caving mining method is primarily used
Breaking down of the hard roofs at different levels will result in the frequent occurrence of a strong 2 ground pressure in stopes, such as crashed supports and damaged roadways that significantly affects the safety of production [3,4]
The support crashing mechanism was studied during the mining of an extra-thick coal seam with hard roofs, indicating that the high hardness of the top coal and the insufficient resistance of the supports were the primary causes of the crashed supports [7]
Summary
Thick and extra-thick coal seams are the primary coal seams of high-efficiency mining, for which the caving mining method is primarily used. Research has been conducted in related areas that consider the effect of strong ground pressure in extra-thick coal seam mining with hard roofs. For the mining of an extra-thick coal seam, the hard roofs at different levels would break owing to the large mining thickness. The method of numerical simulation can directly reflect the structural characteristics of strata fracturing, strength of ground pressure, and stress distribution [10,13,14,15,16,17]. The coal seam thickness is up to 20 m, and the simulation study is primarily aimed at the fracture characteristics of hard roofs at different levels and the corresponding effects of pressure, to reveal the mechanism of strong ground pressures on the working face and provide a theoretical basis for the control of hard roofs
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