西南地区煤层顶板岩溶含水层富水性评价指标体系构建及突水危险性评价
Construction of evaluation index system for water abundance of karst aquifers and risk assessment of water inrush on coal seam roof in Southwest China
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摘要: 西南地区是世界上最大的连片裸露碳酸盐岩分布区,在长期的岩溶作用下,该地区二叠系 煤层顶板的吴家坪组、长兴组、夜郎组玉龙山段等碳酸盐岩地层广泛分布溶洞、洼地、落水洞、地下 暗河等岩溶形态,煤层顶板岩溶含水层富水性强弱具有明显的空间分布不均一性、各向异性。 煤层 开采过程中,一旦顶板导水裂隙带发育高度到达强富水区域,极易造成矿井突水灾害。 根据西南地 区岩溶地下水赋存特征,在考虑因素对含水层富水性影响程度的基础上,从岩溶发育程度、含水层 岩性组合、地质构造、含水层水文地质参数和地形地貌 5 个方面,确定了 12 项评价指标,构建了较 全面的西南地区煤层顶板岩溶含水层富水性评价指标体系。 在此基础上,基于 GIS 和网络层次分 析法(ANP) 建立了煤层顶板岩溶含水层富水性评价模型,实现了典型煤矿煤层顶板岩溶含水层富 水性分区。 同时进一步根据开采厚度、开采深度和岩性组合的空间分布差异,制作了导水裂隙带高 度分区计算图,对不同地质条件下的煤层开采过程进行了数值模拟计算,得到典型煤矿导水裂隙带 发育高度分区计算结果。 利用导水裂隙带高度与目标含水层底板标高进行比较判断突水发生的可 能性,当导水裂隙带到达含水层,则根据含水层富水性的强弱判断突水危险性的大小,以此为原则, 对典型煤矿煤层顶板突水危险性进行了分区评价,并结合以往突水案例,对评价结果的准确性进行 了验证。 提出的西南地区煤层顶板岩溶含水层富水性和突水危险性评价方法可以为相关领域的研 究提供一定的参考。Abstract: Southwestern China is the largest contiguous bare carbonate distribution area in the world. Due to long⁃term karst process in this area,many forms of karst such as karst caves,depressions,sinkholes and disappearing streams are widely distributed in the carbonate strata of Wujiaping formation,Changxing Formation and Yulongshan section of Yelang formation on Permian coal seam roof. The water abundance of karst aquifers above coal seam roof has its own features such as spatial heterogeneity and anisotropy. During the process of coal mining,once the water⁃flowing fractured zone reaches the area of abundant water,it is easy to cause water inrush disasters. According to the occur⁃ rence characteristics of karst groundwater in Southwest China and based on the effects of factors on the water abun⁃ dance of aquifers, 12 evaluation indexes were determined from five aspects in this study, which are the degree of karst development,the lithology association of aquifers,geological structures,the hydrogeological parameters of aqui⁃ fers,and topography and landform. A comprehensive evaluation index system for the water abundance of karst aquifers above coal seam roof in southwest China was established. On the basis of this,an evaluation model of water abundance of karst aquifers above coal seam roof was constructed based on GIS and network analytic hierarchy process (ANP), and the subdivision of water abundance of karst aquifers above coal seam roof of a typical coal mine was achieved. Be⁃ sides,according to the spatial distribution differences of mining thickness,mining depth and lithologic combination,a figure of calculation of subdivision of water⁃flowing fractured zone was made. By carrying out the numerical simula⁃ tion calculation of coal seam mining process under different geological conditions,the calculation results of the heights of water⁃flowing fractured zone in different subdivisions in the typical coal mine were obtained. The possibility of water inrush can be assessed by comparing the height of water⁃flowing fractured zone with the floor elevation of target aquifer. Specifically,when the water flowing fractured zone reaches the aquifer,the risk of water inrush can be deter⁃ mined according to the water abundance of the aquifer. Based on this principle,the risk of water inrush at coal seam roof of typical coal mine was subdivided and evaluated,and the accuracy of the evaluation results was verified by com⁃ bining with previous water inrush cases. The evaluation method of water abundance of karst aquifers and risk of water inrush at coal seam roof in southwest China proposed in this study can provide certain reference for the research in the related fields.