Main and sub-key strata activities characteristics and their control laws on movements of overburden stratum in mining of especially-thick coal seam

Main and sub-key strata activities characteristics and their control laws on movements of overburden stratum are the main basis of studying the roof control in mining of especially-thick coal seam.According to the geological and the occurrence conditions of Laosangou mine field,with method of physical simulation experiment,the paper analyzes the main and sub-key strata activities characteristics and their control laws on movements of overburden stratum in coal mining of Laosangou mine field in central part of Zhungeer.The result shows that the first weighting interval of basic roof(sub-key stratum) is 45m or so,and the periodic weighting interval is between 15~20m;when the working face advances about 130m,the bending subsidence of the main key stratum will increase,and the longitudinal cracks will happen at its two ends,while the overburden stratum in the central part of the gob is compact,and cracks are gradually closed;the existence of the key strata structure decreases the impact of wide ranging severe activities of overburden stratum in the mining process on the working face.