厚黄土覆盖区煤矿开采对松散含水层地下水影响机理的研究

In the area overlaid with thick loess, there often exist the unconsolidated aquifer which has great thickness, good water quality and good water yield property, and it has become the main aquifer for local economic development. Practice for many years shows that, the height of water flowing fractured zone does not reach to water-resisting floor of the unconsolidated aquifer in the area overlaid with thick loess, it has no direct effect on the unconsolidated aquifer. But due to the dewatering of the aquifer below water flowing fractured zone, it causes that the groundwater of unconsolidated aquifer seepage downward by the way of leakage from the weak permeable layer, and causes the decline of groundwater level and even the dewatering of the unconsolidated aquifer. This project taking S6-9 working face of Changcun coal mine as the experimental research base, using similar material simulation experiment, rock fracturing test, permeability test, numerical simulation and so on, to analyze the regularity of the movement and deformation failure of the unconsolidated aquifer, to study the law of the development of rock fracture and the change of permeability, to discuss the influence of coal mining on groundwater of the unconsolidated aquifer at different thickness of coal seam and the effect of the change of water-resisting floor thickness, permeability character on the dewatering of the unconsolidated aquifer. From the study of this project, it can provides theoretical basis for the protection of groundwater resources of unconsolidated aquifer in mining area of the northwest of China, and it has a very important practical significance for promoting the coordinated development of mine resources and environment.

厚黄土覆盖区往往存在着厚度较大、水质良好、水量较丰富的松散含水层，成为当地国民经济发展的主力含水层。多年实践表明，厚黄土覆盖区煤矿开采形成的导水裂隙带往往没有触及到松散含水层的隔水底板，对松散含水层不产生直接影响。但是，由于采煤造成导水裂隙带以下含水层的疏干，使得松散含水层地下水将通过弱透水层以越流的方式向下渗漏，导致松散含水层地下水水位下降甚至被疏干。本课题以常村煤矿为试验研究基地，运用相似材料模拟实验、岩石压裂实验、渗透实验、数值模拟计算等方法，分析厚黄土覆盖区煤矿开采引起松散含水层的变形破坏规律，研究采动岩体裂隙发育及其渗透性变化规律，探讨煤矿不同开采条件对松散含水层地下水的影响及隔水底板厚度和渗透性质改变对松散含水层疏干过程的影响等。通过本课题研究，可为我国西北部矿区松散含水层地下水资源的保护提供理论依据，对促进矿区资源与环境协调发展具有十分重要的现实意义。

厚黄土覆盖区煤矿开采形成的导水裂隙带没有触及到松散含水层的隔水底板，不会对松散含水层产生直接影响。但是，由于采煤造成导水裂隙带以下含水层的疏干，使得松散含水层地下水将通过弱透水层以越流的方式向下渗漏，导致松散含水层地下水水位下降甚至被疏干。本项目以常村煤矿为实验研究基地，采用相似材料模型试验，深入研究了不同开采背景下覆岩采动破坏特征与裂隙分布规律，以及采动破坏对上覆松散含水层地下水位的影响程度与破坏机理。在对采空区上覆岩层不同部位裂隙率统计的基础上，分别对冒落带与裂隙带内破碎岩体的渗透性进行测定，建立起冒落带、裂隙带内渗流速度与水力梯度的非线性关系，拟合出采空区不同部位岩体的渗透系数。以GMS为平台，构建常村煤矿的三维地下水非稳定流数值模型，结合采动岩体渗透系数的变化，预测煤矿不同开采条件下、隔水层参数变化条件下以及松散含水层不同水动力条件下采煤对松散含水层的影响。研究发现：导水裂隙带的发育受到覆岩厚度、开采厚度及主关键层的综合影响。松散含水层隔水底板的曲率变化是影响松散含水层的直接因素。导水裂隙带发育高度、松散含水层隔水底板性质与孔隙含水层特征是松散含水层地下水受矿井开采影响程度的核心要素。项目研究成果形成了一套完整的关于厚黄土覆盖区煤矿开采对松散含水层地下水影响机理的理论，对促进厚黄土覆盖区松散含水层地下水资源保护具有重要理论和现实意义。