Main roof first collapse law and measure of controlling roof in seam with approximate shallow depth

Based on the exploitation of 2301 coal face,the first weighting step of main roof is analyzed and calculated by utilizing two mechanics model of beam and board.Combining actual collapsed step of main roof,the mechanics model that is fit to the geological condition of approximate shallow coal seam has been confirmed.Moreover,in condition of the different boundary the first weighting step of main roof is calculated.In order to solve the problem that the first weighting step of main roof is oversize,according to characteristic of the first weighting step of main roof when scope is in condition of the diffetent boundary,the paper has proposed method of the deep-hole presplitting explosion and the sector coal pillar width reduction to make the stope in clamped both and simply supported both sides stress condition.Thus,the first weighting step of main roof may be reduced,and the roof safety of coal face is guaranteed during coal mining and roof breaking down for the first time.