Numerical simulation study on the pressure relief and anti-scour effects of multi-seam coal mining

Existing studies on pressure relief and anti-scour in multi-seam coal mining mostly rely on simplified numerical models to analyze the mining-induced stress distribution of multiple coal seams, which makes it difficult to realistically reflect the complex geological conditions and the physical-mechanical interactions between coal seams. Moreover, there is a lack of systematic characterization of the combined influence mechanisms of goaf areas and remaining coal pillars. To address these issues, based on the engineering background of mining four coal seams in Kuangou Coal Mine, this study used numerical simulation to investigate the impact of complex spatial structures such as multi-seam goaf areas and remaining coal pillars on the mining of underlying coal seams. The results showed that: when mining a single coal seam, there was obvious stress concentration below the remaining coal pillar, and a significant pressure relief effect below the goaf area. Under the superimposed influence of mining multiple seams, the stress concentration at the overlapping boundaries of multiple goaf areas further increased. If there were goaf areas above and below the remaining coal pillar, its stress concentration significantly decreased, resulting in a stress reduction in the coal seam below the projection of the remaining pillar, thus causing pressure relief. The protective pressure relief effect of goaf areas and the stress concentration effect of coal pillars decreased as the spacing between coal seams increased. According to the coal seam stress concentration coefficient, the coal seam protection pressure relief zones and stress concentration zones were delineated: when the stress concentration coefficient was (0,1], (1,2], (2,3], and (3, ∞), they corresponded respectively to pressure relief or no influence zone, weak influence zone, moderate influence zone, and strong influence zone. Electromagnetic radiation and acoustic emission energy in the delineated areas were tested using an electroseismic vector monitoring instrument, and the results verified the accuracy of the delineated pressure relief and stress concentration zones.