山区多煤层重复采动下地表变形特征

Characteristics of surface deformation under repeated mining in mountainous area

西山煤田开采逐步向深部延伸,重复采动下应力对围岩的切割作用不断加重,在山区采动滑坡作用下地表变形加剧、产生大量地裂缝且存在形成地表水下渗通道的可能。以西曲矿18401工作面为研究对象,综合应用集InSAR动态观测、地表勘察、微震监测和数值模拟为一体的地表变形监测与分析体系,探讨山区多煤层下行开采地表变形特征。研究结果表明:18401工作面推进80~90 m过程中关键层发生破断,致使地表开始发生明显的沉降,煤层重复采动引起的地表移动活跃期为2~3个月,长于单煤层开采地表移动活跃期,终采后地表达到充分沉降的滞后周期为6~9个月;采场上覆陡坡处的地表沉降和地裂缝发育程度皆大于平缓处,陡坡处附近地表发生大范围拉伸破坏,形成台阶裂缝,采动滑坡作用下台阶裂缝高度增加了10.67%,但相比于地形作用,煤层重复采动对地表变形仍占据着主导作用;形成山区地形与煤层重复采动作用下的地表塌陷分区,研究结果可为西山矿区类似矿井地表塌陷预防及生态环境治理工作提供科学指导与借鉴经验。

With continuous exploitation towards depth of of Xishan coalfield, the cutting effect of stress on surrounding rock under repeated mining is increasing. The surface deformation is intensified under the action of mining landslide in mountainous area, a large number of ground fissures are produced, and it is possible to form surface water infiltration channels. With No.18401 panel of Xiqu Coal Mine as the research object, surface deformation characteristics of multi-seam mining in mountainous area were discussed by comprehensively applying surface deformation monitoring and analysis system integrating InSAR dynamic observation, surface exploration, microseismic monitoring, and numerical simulation. The results have indicated that the key stratum fails during the advance of 80-90 m of No.18401 panel, resulting in obvious surface settlement;the active period of surface movement caused by repeated mining of coal seam is 2-3 months, which is longer than that of single coal seam mining, and the lag time of full settlement after final mining is 6-9 months. The surface subsidence and fissures development at the slope ground of the panel are greater than those at the gentle ground, and large-scale tensile failure occurs near the slope ground, leading to step cracks;the height of step crack increases by 10.67% under the action of mining landslide. However, compared with topographic effect, repeated mining of coal seams still plays a leading role in surface deformation. The subregion of surface collapse under the action of mountainous terrain and repeated mining of coal seams is formed. The findings can provide scientific guidance and reference for the prevention of surface subsidence and ecological environment management of similar mines in Xishan mining area.