关键词: 沿空留巷, 预切顶, 厚硬直接顶, 卸压机理, 长“悬臂梁”

Abstract: The No.9 coal seam of Yunjialing Mine is overlying thick and hard rock strata, and the mine pressure in the stope is strong. It is difficult to control the surrounding rock by using the traditional gob-side entry retaining method. Based on the transportation roadway of 19103 working face in Yunjialing Mine, the mechanical equilibrium conditions of thick and hard immediate roof of gob-side entry retaining with roof cutting are analyzed, and it is concluded that the support resistance of no less than 1046kN should be provided beside the roadway. The numerical simulation method was used to compare the deformation and stress of surrounding rock and the distribution of plastic zone of gob-side entry retaining with and without roof cutting under the condition of thick and hard direct roof. The results show that the roof of goaf is more likely to collapse after roof cutting. The subsidence of the roof of the retaining roadway is only 28.2 % of that without roof cutting in the same period. After roof cutting, the vertical stress of the roof on the side of the retaining roadway becomes smaller, the horizontal stress increases and the plastic zone of the surrounding rock transfers to the deep part of the roof and floor. It is revealed that the mechanism of pre-splitting roof cutting pressure relief is to block the transmission of dynamic pressure in the working face and induce the roof of the goaf to fall in ad-vance to meet the roof pressure. The reason for the increase of horizontal stress is the result of the deformation of the long and short ' cantilever beam ' formed on both sides of the slit. The roof control idea for gob-side entry retaining with thick and hard immediate roof is proposed as centralized support of the cutting end, appropriate pressure relief and formation of “combined can-tilever beam”. The comprehensive support technology of long and short anchor cable, single hydraulic prop and yielding U steel beam is adopted, and the sealing measures of hanging net shotcrete are adopted. The field industrial test results are good, the peak stress of the anchor cable of the roadway roof after cutting the roof is about 350kN, the roadway section is 2.95m×2.44m (width × height) after the surrounding rock is stable, and the specifications meet the conditions of secondary reuse. The technology has been successfully applied in the subsequent No.9 coal face in Yunjialing Mine.