煤炭开采对相邻区域生态潜水流场扰动特征

Disturbance characteristics of coal mining to the eco-phreatic flow field in adjacent regions

  • 摘要: 陕北煤炭能源基地高强度开采易影响生态潜水的自然径流条件,针对自然保护区周边煤炭资源开采对地下水流场的扰动问题,以榆神矿区某井田为例,通过构建研究区煤-水空间结构水文地质模型,系统分析研究区生态潜水的赋存特征及其规律;采用物理模拟、数值模拟、现场实测等手段,综合分析煤层覆岩岩性组合结构、煤层与关键层间距、煤层厚度、煤层埋深、工作面长度等因素,利用相关分析方法提出了适合于研究区导水裂隙带高度计算的裂采比公式;根据水文地质条件和煤层采动方式,采用地下水数值分析方法,模拟了煤炭开采后萨拉乌苏组生态潜水流场变化,分析了煤层采动后生态潜水受扰动的特征。研究结果表明:区内萨拉乌苏组生态潜水含水层全区发育,其赋存受基岩面形态控制,生态潜水水位受地形、含水层厚度、地下水分水岭和地表水等影响;下伏关键隔水层(保德组红土)受沉积影响在研究区东南局部缺失,形成“天窗”导水通道;区内覆岩结构以硬-软-硬、硬-硬-软2种组合类型为主,覆岩结构类型对导水裂隙带发育高度及形态有重要作用;统计分析多个导水裂隙带发育高度结果,提出榆神矿区导水裂隙带最大裂采比为28.1倍,该数值对榆神矿区保水采煤及水害防治具有重要指导意义;通过计算发现,研究区内东南部保德组红土缺失区覆岩采动裂隙将发育至生态潜水含水层,造成生态潜水漏失与水位下降。为保护生态潜水资源,建议开采研究区东南部“天窗”部位的煤层时,必须采取相应的保水采煤技术。

     

    Abstract: The natural runoff condition of high intensity mining in north Shaanxi coal energy base is easy to affect eco- phreatic in its adjacent regions. In this paper,aiming at the disturbance of coal resource exploitation to groundwater flow field around nature reserve,a mine field in Yushen mining area is studied. By constructing the hydrogeological model of coal-water spatial structure,the occurrence characteristics and its law of eco-phreatic in the study area are analyzed systematically. By means of physical simulation, numerical simulation and field measurement, the combined structure of coal overburden lithology,the distance between coal seam and key layer,the thickness of coal seam,the depth of coal seam,the length of coal face and so on are analyzed synthetically. The correlation analysis method is used to propose the height of the fractured zone suitable for the study area. According to the hydrogeological conditions and the mining mode of coal seam,the change of eco-phreatic flow field of Sarawusu formation after coal mining is simula- ted by using the method of numerical analysis of groundwater,and the characteristics of disturbance of eco-phreatic af- ter coal seam mining are analyzed. The results show that the eco-phreatic of Sarawusu formation is developed in the whole area and its occurrence is controlled by the form of bedrock surface,and the eco-phreatic level is affected by to- pography,aquifer thickness,groundwater watershed and surface water. Under the influence of sedimentation,the key layer is missing in the southeastern part of the study area to form a “ skylight” aqueduct. The overburden structure is mainly composed of hard-soft-hard and hard-hard-soft. The type of overburden structure plays an important role in the development height and shape of the water fractured zone. Based on the statistical analysis of the development height of several water fractured zone,it is proposed that the maximum fissure ratio is 28. 1 times in Yushen mining area,which has an important guiding significance for water-preserved mining and water hazard prevention in Yushen mining area. It is found that after coal seam mining, the loss of red soil in Baode formation in the southeast of the study area will re- sult in the loss of eco-phreatic water and the decline of water level,with a maximum depth of 10 m. In order to protect the eco-phreatic water resources,it is suggested that when mining the coal seam of the “ skylight” in the southeast part,the corresponding water-preserved mining method must be adopted.

     

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