Stability of Coal Pillars and Backfill Due to Intermittent Cut-and-Fill Mining Under Loose Aquifer

Coal pillars provide temporary or permanent support to the overburden strata. Thus, coal pillar design and stability are two of the most complicated and extensive issues in mining safety assessments. In this study, an investigation on the effects of intermittent cut-and-fill mining under loose aquifer on the stability of coal pillars and backfill was presented using the theoretical analysis. Considering the time dimension, the four-dimensional evaluation model of overburden failure based on GIS was established to effectively control the deformation and failure of the overlying rock, which can quantitively evaluate and analyse the spatial characteristics and the height of the water-conducting fractured zone over time for the intermittent cut-and fill mining. Theoretical analysis in the mining process shows that when the coal pillar width is less than the mining width of 1/3, then the coal pillar could not bear the load of the overburden, and the backfill body could ensure the stability during the process of coal mining. The dynamic change of the overlying rock failure with time was monitored in different time to repeat the same measuring point. The four-dimensional model of overburden failure based on GIS makes the overburden failure law develop from static simulation research to dynamic monitoring The intermittent cut-and-fill mining could effectively guarantee the stability of coal pillar in the process of coal mining, solving the problem of mining under the loose aquifer, and having a good reference to engineering practice.