榆神矿区中深煤层开采松散含水层地下连续墙侧向截水帷幕可行性分析

Feasibility analysis of lateral water interception curtain in loose aquifer during deep coal seam mining in Yushen mining area

  • 摘要: 榆神矿区是陕北煤炭基地的主力矿区,高强度煤炭资源开发过程中煤层顶板水害与地下水资源流失问题突出,随着黄河流域生态环境保护战略的全面推进,对矿井水防治与水资源保护提出了超前化、主动化、源头化的地质保障要求。笔者针对陕北榆神矿区井工煤矿煤层开采影响下近地表富水松散含水层涌(失)水问题,借鉴露天大水矿区地下连续墙的帷幕减渗成功经验,从稳定的补给水源、相对集中补给通道、防绕流托底3个方面总结了煤矿区开展地下水连续墙截水帷幕的基本条件;通过建立井工煤矿开采与松散富水含水层帷幕条件下矿井涌水量理论计算模型,得出截水帷幕墙体渗透能力越弱、厚度越大,以及距离采掘范围越近是减少煤层顶板近地表松散含水层涌(失)水的基本原理。以榆神矿区某矿工作面集中涌水问题对研究对象,依据井工煤矿地下水连续墙帷幕减渗基本原理,分析得出工作面集中涌水区段主要水源以近地表松散含水层地下水为主,且具备稳定可观的动态补给,煤层开采形成的导水裂隙突破顶板隔水土层揭露松散层内条带状古河道(古河道内隔水土层变薄、松散层增厚),形成了相对集中的涌水通道,以及在“上含下隔”(上为富水松散含水层,下为相对隔水土层)的防绕流托底组合结构下,认为该区段具有建造侧向截水帷幕墙的可行性。并建立了案例矿井正常开采与侧向帷幕墙建设条件下地下水系统数值模型,模拟结果显示,在工作面外围局部侧向帷幕工况下(侧向帷幕墙体长度600 m),帷幕墙体内外松散含水层地下水水位梯度显著加剧,但由于松散含水层良好的渗透性,以及井田地面东高西低地形地貌控水条件,帷幕墙体外围近地表松散层地下水水位整体未发生明显抬升,原来通过薄基岩区、松散层增厚带进入工作面采空区的地下水径流量沿帷幕墙体外围导流至下游,600 m长侧向截水帷幕整体减水效率28.43%。研究成果为榆神矿区井工煤矿开展基于侧向截水帷幕的顶板水害防治与地下水资源保护可行性分析提供了科学依据。

     

    Abstract: Yushen mining area is the main mining area of the coal base in northern Shaanxi at present. During the development of high-intensity coal resources, the problems of coal seam roof water disaster and water resource leakage are prominent. with the comprehensive promotion of the ecological environment protection strategy in the Yellow River Basin, advanced, proactive, and source oriented geological guarantee requirements have been put forward for mine water prevention and water resource protection. the article focuses on the problem of water inrush (loss) in the loose water bearing layer near the surface under the influence of underground coal mining in Yushen mining area, Shaanxi Province. Drawing on the successful experience of curtain seepage reduction in open-pit large water mining areas, the article summarizes the basic conditions for carrying out underground continuous wall water interception curtains in coal mining areas from three aspects: stable supply water sources, relatively concentrated supply channels, and the waterproof layer conditions to prevent groundwater from flowing around; a theoretical model of water inflow under the condition of loose water rich aquifer curtain in underground coal mines is established. It is concluded that the weaker the permeability and thickness of the cut-off curtain wall, and the closer it is to the mining range, are the basic principles for reducing water inrush in the loose aquifer near the surface of the coal seam roof. Taking the problem of concentrated water inflow in a coal mining face in Yushen mining area as the research object, based on the basic principle of groundwater continuous wall curtain seepage reduction, it is analyzed that the main water source in the concentrated water inflow section of the working face is the loose aquifer groundwater near the surface, which has stable and observable dynamic recharge. The water conducting cracks formed by coal seam mining break through the roof waterproof soil layer and expose the strip-shaped ancient river channel inside the loose layer (the waterproof soil layer inside the ancient river channel becomes thinner and the loose layer becomes thicker), forming a relatively concentrated water inflow channel. Under the combination structure of "upper aquifer and lower barrier" (the upper layer is the rich water loose aquifer, and the lower layer is the relatively waterproof soil layer), it is believed that this section has the feasibility of constructing a lateral waterproof curtain wall. and a numerical model of the groundwater system was established for the working face under normal mining and curtain wall construction conditions. The simulation results showed that under local curtain wall conditions around the working face, the groundwater level gradient in the loose aquifer around the curtain wall was significantly intensified. However, due to the good permeability of the loose aquifer and the low terrain and water control conditions of the mining field, the groundwater level in the loose layer near the ground did not significantly rise. The groundwater runoff that entered the goaf through the thin bedrock area and the thickened strip of the loose layer was diverted downstream, and The overall water reduction rate under the construction conditions of a 600 m long lateral cut-off curtain wall is 28.43%. The research results of the article provide a scientific basis for the feasibility analysis of roof water damage prevention and groundwater resource protection based on water interception curtains in the Jinggong Coal Mine of Yushen Mining Area.

     

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