深部低渗透强突出煤层群首采下保护层确定和效果考察

Determination and effect investigation on the first mining lower protective layer in deep coal seam group with low permeability and strong outburst

软岩保护层在深部低渗透强突出煤层群首采保护层选择中具有潜在的应用前景。在阐述下保护层开采覆岩移动与采场裂隙演化及瓦斯运移关系的基础上,以芦岭矿为工程背景,通过FLAC3D数值试验,研究软岩保护层开采后的卸压效果,并和不同层位的薄煤层开采卸压效果对比分析。结果表明,在采厚相同的情况下,开采10煤保护层相对于软岩保护层,卸压程度弱,保护范围小,保护效果差。软岩保护层开采后,被保护层处于弯曲下沉带的下限范围。受采动影响,有大量的离层裂隙生成。考察期范围内上覆被保护层(8、9煤层)瓦斯抽采率达62.9%,表明软岩保护层开采能够对上覆被保护层(8、9煤层)起到显著的卸压效果。研究结果可为其他矿区保护层开采选择提供参考,丰富国内保护层开采实践。

The soft rock protective layer has the potential application prospect in the selection of first mining protective layer for the deep coal seam group with low permeability and strong outburst. The relationship of the overlying strata movement in lower protective layer mining with the stope fracture evolution and gas delivery was discussed. On this basis,taking the Luling Mine as engineering background,the pressure relief effect after the soft rock protective layer mining was studied through FLAC3 D numerical tests and compared with the pressure relief effect of thin coal seam mining in different position. The results showed that when the mining thickness was same,compared with the soft rock protective layer,the degree of pressure relief was weaker,the protection range was smaller,and the protection effect was worse for mining No. 10 coal protective layer. After the mining of soft rock protective layer,the protected layers were in the lower limit range of bending subsidence zone. Large amount of delamination fracture generated by the influence of mining. The gas extraction rate of overlying protected layer（ 8,9 coal） can reach 62. 9 % during the investigation period,which indicated that the mining of soft rock protective layer could play a significant pressure relief effect for the overlying protected layers（ No. 8 and 9 coal seam）. The results can provide references for selection of protective layer mining in other mining areas,and enrich the practice of protective layer mining in China.