煤层开采覆岩预裂–注浆改性失水控制方法探讨

Discussion on roof water loss control method of coal seam based on pre-splittinggrouting reformation(P-G)

陕北榆神矿区煤层开采面临顶板水害防治与水资源协同保护技术需求,根据材料力学、断裂力学相关理论,以及不同覆岩类型的采动裂隙带统计成果,提出基于预裂–注浆改性(P-G)的煤层顶板失水控制技术思路,其基本原理为通过压裂工艺将连续性好的基岩层压裂成非连续性岩层,削弱采动导水裂隙在坚硬岩层中向上扩展的“尖端效应”,抑制导水裂隙发育高度。再采用黏土类软弱注浆材料将岩层改性为相对软弱的岩层,起到抑制导水裂隙带向上发育与降低上覆岩层导水能力的双重作用,从而实现煤层顶板含水层失水控制。本文以陕北能源基地榆神矿区为对象,提出以采煤工作面地质与水文地质条件分析,采煤工作面顶板含水层涌(失)水模式识别,P-G模式、层位与时间确定,顶板岩层水平孔水力压裂与注浆改性为主要思路,对榆神矿区采煤工作面顶板含水层失水控制方法进行了探讨,为我国陕北能源基地榆神矿区顶板水害防治和水资源协同保护技术实践提供一定的借鉴。

In view of the technical requirements of roof water disaster prevention and water resources collaborative protection faced by coal mining in western coal mining area,this paper puts forward a technical idea of roof water loss control based on pre-splitting grouting reformation(P-G)according to the strain strength theory of material mechanics and the statistical results of mining fracture zones of different overburden types.The basic principle is that the continuous bedrock layer will be fractured into discontinuous rock layers by fracturing technology,and by weakening the“tip effect”of upward expansion of mining induced water flowing fracture in hard rock stratum to restrain the development height of water flowing fracture.Then,the soft clay grouting materials are used to modify the strata into relatively weak ones.Therefore,the P-G method plays a dual role in restraining the upward development of the water flowing fracture zone and reducing the water conductivity of the overlying strata,so as to realize the water loss control of the coal seam roof aquifer.Taking the Yushen Mining Area in the energy base of northern Shaanxi as the analysis object,this paper discusses the control method of P-G water loss in roof aquifer before mining,including the analysis of geological and hydrogeological conditions,the identification of water inflow(loss)pattern of aquifer in coal working face,prediction of development height of water flowing fracture zone,water gushing mode of overburden rock,determination of P-G time,horizon and time,horizontal hole hydraulic fracturing of roof strata and grouting modification.It has certain reference significance for roof water disaster prevention and water resources coordinated protection technology practice in Yushen Mining Area of the energy base in northern Shaanxi.