Study on effect of interburden on movement of overburden in multiple coal seams

Based on the overburden movement of lower coal seam with multiple coal seams in western diggings，theoretical derivation，numerical simulation and field test are applied to study effect of three factors，thickness and lithology，the proportion of hard rock，the ratio of the overburden thickness to the interburden thickness，on the movement of overburden during the mining process of lower coal seam.A theoretical calculation method is put forward to calculate the roof fracture height which provides a reference for theoretical calculation of the height of fracture zone development in working face； The theoretical calculation of the height of fracture zone development in stope and the breakage distance of hard rock in working face was verified by using numerical simulation to simulate overburden movement and breakage law； Finally，the validity of theoretical calculation and numerical simulation is verified by the field measured roof weighting and breakage data.After research and analysis：①A method for calculating the height of a fracture zone by comparing the maximum deflection with the free space is proposed.②The fracture development in the roof strata is determined by the mining height.The mining height is proportional to the development height of fracture zone，and the nature of overburden also has a significant impact on the development of cracks.③The ratio of the overburden thickness to the interburden thickness is not the dominative factor for overburden movement.If there is a thick and hard rock stratum in the middle stratum，the overburden movement will be reduced.④The breakage of thick and hard intermediate strata has a decisive influence on the movement of overlying strata.