Study on top bag filling roof supporting technique in thick coal seam roadways developing along roof

In order to solve the problem of a large amount of loss in the bottom of the working face caused by mining along the bottom of the working face, and to improve the recovery rate of coal resources, the mining roadway along the top of thick coal seam is carried out to mine the bottom coal in advance. It is necessary to reduce the influence of the ultra-high mining roadway on the normal mining of the working face because of the formation of the ultra-high mining roadway in the advance excavation of the bottom coal mining. The mine originally used wood cribs to reduce the height of the retracted roadway to keep the ultra-high mining roadways stable, but the wood fill support labor intensity was large, the efficiency was low, the top contact was insufficient, the carrying capacity was low and easy to deform, the working resistance of the single support was small, the force was uneven, the stability was poor, and itwas prone to fall, which posed a serious threat on the safety retreating of the working surface. Based on the above reasons, combined with field mining technical condition of Hetuo coal mine, the mining techniques for carrying the top bag filling using a double liquid grouting material was proposed to use. The implementation of this technology was to build a filling body support platform in the middle of the roadway. The platform was supported by a single pillar with a filling bag on the platform, the top of the filling bag was hanging on the top plate of the roadway, the filler bag was free to face the barrier, the metal net, and the board (prevent filling bags from being bloated).Filling the bag with the air to fully fill the space, then fill the slurry with a high-speed pulper. After on-site experiment, the results show that the ultra-high retreating roadway uses a new type of grouting material to implement top filling technology supporting strength of single pillar is 12.3～25.7 MPa,high efficiency, effectively improve the integrity and stability of the top of the section roadway.