Research on Novel Method of Gob-Side Entry Retaining under the Synergistic Effect of Roof Cutting and Roadside Filling in Thick Coal Seams

With the increase of coal seam mining thickness, the caving height of stope roof, the mining-induced stress increase, and the control difficulty of gob-side entry retaining increase. To apply the gob-side entry retaining (GER) technology in thick coal seams, optimize the support method and reduce the deformation, based on directional energy-gathering blasting technology and roadside filling technology, gob-side entry retaining with synergistic roof cutting and roadside filling (GER-RCRF) is proposed. Through theoretical analysis, numerical simulation and field experiments, the mechanism and effect of the method are analyzed. The results show that due to the stress relief of roof cutting, the pressure of the solid coal rib and the roadside filling of the GER-RCRF is reduced, and the stress concentration area shifts to the deep rock mass. Under the condition of roof cutting, the stress of roadside filling is distributed in a “single peak”, and with the width increases, the peak stress first increases and then decreases, and then increases and then decreases. Meanwhile, the roof cutting height should be based on the broken and expansion effect of the rock strata, considering the key stratum effect of the rock layer. The stress of the surrounding rock is further reduced when the overlying key strata is cut off. Finally, the GER-RCRF has successfully reduced the stress of roadside filling, roof and solid coal rib, optimized the stress environment of surrounding rock, and successfully realized the purpose of gob-side entry retaining. The field test verified the effectiveness of GER-RCRF. The stress of roadside filling and the deformation of surrounding rock are significantly reduced. The research results provide a certain degree of scientific basis for the successful application of gob-side entry retaining in thick coal seam.