Collapse behavior and control of hard roofs in steeply inclined coal seams

The control of hard roof collapse in steeply inclined coal seams is a difficult problem in coal mine operations. We used the Linsheng coal mine as the engineering background and investigated the collapse behavior of hard roofs in horizontal and steeply inclined coal seams using discrete element numerical methods. We designed a pre-splitting blasting scheme of hard roofs in steeply inclined coal seams according to collapse characteristics and performed numerical simulations using discrete element methods. The scheme was applied in the Linsheng coal mine and achieved good results. The hard roof rocks clearly exhibit elastic-brittle plastic failure characteristics; we therefore applied an elastic-brittle plastic strain softening constitutive model to calculate the failure process of the coal strata contact surface, which reasonably reflects the failure characteristics of steeply inclined coal strata roofs. We determined the relationship between the coal seam dip angle and roof collapse degree using discrete element methods to obtain the roof collapse law of horizontal and steeply inclined coal seams. We propose a numerical calculation method of advanced deep-hole pre-split roof blasting using discrete element methods. The obtained numerical results are consistent with field applications, which verify the feasibility of the proposed method in studying hard roof control.