Study on stress evolution law of upper coal seam in long-distance advance mining of lower coal seam

With the shift of coal resources to deep mining, the occurrence of long-distance coal seams has increased, and protective layer mining is facing new challenges. This paper attempts to explain the stress evolution law of the upper coal group in the long-distance mining of the lower coal group in Pingdingshan No. 8 Coal Mine. A simulation model of advance mining of lower-group coal long-distance was established. The stress evolution law of the upper coal seam under the influence of advanced mining disturbance of the lower coal seam is studied. The following conclusions were obtained: The advance mining of the lower coal group had a positive or negative impact on the stress distribution of the upper coal seam group. With the recovery of the lower coal group of the F-21030 working face, the overburden of the F-21030 goaf finally formed a "Y" type pressure relief area. The pressure relief effect of the E-21070 working face near the stopping line was obvious. The coal seam of Group E was divided into three areas affected by the advance mining of the lower coal seam. The maximum pressure relief value was 6.6% lower than the initial stress. According to the simulation results, the E-21070 working face was divided into three regions, namely, the pressure relief region, the stress increase region, and the original stress region. According to the field drainage results of pressure relief gas, the extraction curve could be divided into three parts, namely, the stable area, pressure relief area, and stress recovery area. The maximum pure gas drainage volume could reach seven to eight times of the original area. The pressure relief extraction effect was remarkable, and the optimal extraction range was 22-210 m behind the coal face of the group.