Mining safely under a coal seam while protecting an overlying roadway

To ensure the stability of an overlying roadway in close proximity to a 1000-m deep coal seam, this work, through theoretical analysis and numerical simulation, studies the deformation and failure mechanism, failure types, and prevention methods of the overlying roadway while mining a lower coal seam. Based on the study of mining conditions and overburdened space structures formed through mining, the deformation and failure law of the roadway in the strike and dip directions is obtained. Moreover, the stress evolution law of roadway deformation and failure is obtained by studying the influence of different mining stages and filling rates of the lower face on the mining of the overlying roadway. Results show that there are two types of potential roadway deformation and failure: (1) roadway section reduction failure and (2) roadway strike step subsidence failure. The fundamental cause of the deformation and failure of the overlying roadway is the influence of the large buried depth, strong mining stress, and unequal distance between the coal seam and roadway. The direct causes are the sudden increase in the stress of the roadway surrounding the rock and the subsidence of the key strata. In the mining process, when the mining range of the working face is more than 400 m, the roadway section reduction failure and strike ladder subsidence failure superimpose each other, inducing further roadway failure. Therefore, a scheme of partial filling and strengthening of the roadway along the working face is designed. Field measurements revealed that the above scheme can meet the stability requirements of the overlying roadway and the high efficiency and yield of the underlying working face. The results provide some references for the safe mining of coal in the 1000-m deep coal seam.