蒙陕矿区深部煤层开采顶板含水层失水特征与钻孔注水帷幕保护分析

Analysis on water loss characteristics of roof aquifer and borehole hydraulic curtain protection in deep coal mining in Inner Mongolia‒Shaanxi mining area

我国蒙陕接壤深部矿区主采煤层赋存地质与水文地质特征较之浅部矿区差异较大。文章通过系统分析呼吉尔特、台格庙、新街等蒙陕深部矿区主采煤层地质、水文地质特征以及采动导水裂隙等相关研究成果,总结出巨厚白垩系孔隙−裂隙含水层作为矿区保水目标层,在侏罗系安定组砂质泥岩弱隔水关键层间隔保护下,在煤层开采驱动下易形成典型的间接涌(失)水模式。并以研究区案例矿井为分析对象,数值模拟深部煤层开采过程中地下水流场变化规律。结果显示,煤层回采扰动下地下水流场以采掘空间为中心形成降落漏斗,并随着回采进尺的增加,降落漏斗影响范围与工作面总涌水量均增加,上部白垩系含水层越流失水量增加幅度小于总涌水量增加幅度,模拟结果与案例实测结果基本一致。最后,针对深部煤炭资源开采与研究区水源地保护“煤−水矛盾”问题,以保护白垩系含水层地下水水位为目标,提出以白垩系为回灌层、安定组顶部为终孔层位、注水井尽量远离煤矿区为基本原则的白垩系含水层地下水水位钻孔注水帷幕保护思路。并模拟分析案例矿井在正常开采与注水帷幕墙体建设条件下白垩系含水层地下水流场的变化规律,结果显示“钻孔注水帷幕”在低渗透性含水层水位保护具有较好的可行性,对于深部矿区煤层开采顶板水资源保护具有借鉴意义。

The geological and hydrogeological characteristics of the main mined coal seams in the deep Inner Mongolia‒Shaanxi Mining Area vary greatly from that of the shallow area.Herein,the relevant research results on the geological and hydrogeological characteristics,as well as the mining-induced water-flowing fracture,were analyzed sys-tematically for the main mined coal seams in the deep mining areas,such as Hujierte,Taigemiao and Xinjie.On this basis,it is summarized that a typical indirect water loss(inrush)mode could be formed easily under the drive of coal mining,with the protection of key weak water barrier layer of Jurassic Anding Formation sandy mudstone,taking the thick Cretaceous pore-fissure aquifer as the target water-conserving layer in the mining area.Besides,analysis was per-formed based on the case mine in the study area,with the change rule of groundwater flow field during the mining of deep coal seams simulated numerically.The simulation results show that:the groundwater flow field under the disturb-ance of coal seam mining basically forms a falling funnel with the mining space as the center,and the impact area of the falling funnel is expanded with the increase of mining footage,having the total water inflow of working face increasing linearly.Additionally,the increasing amplitude of water loss of the upper Cretaceous aquifer is less than that of the total water inflow.Generally,the simulation results are basically consistent with the measured results in case study.Finally,in view of the contradiction between deep coal resources exploitation and water source protection in the study area,the borehole hydraulic curtain protection of groundwater level in the Cretaceous aquifer was proposed based on the basic principle of taking the Cretaceous system as the reinjection layer,and the top of Anding Formation as the final hole hori-zon,with the reinjection well as far away from the coal mine area as practical,for the purpose of protecting groundwater level of Cretaceous aquifer.Moreover,the change rule of groundwater flow field in the Cretaceous aquifer under the conditions of normal mining and hydraulic curtain wall construction in the case mine was simulated and analyzed,which shows that the borehole hydraulic curtain has good applicability for the level protection of low permeability aquifer,with reference significance for the water resource protection in mining roof of deep coal mining area.