多层次地质结构场地地下水防污性能实例介绍

Discussion on Groundwater Vulnerability of Aeration Zone in Multi-level Geological Structure

基于钻探资料,场地地质结构自上而下依次为土层、白云岩、泥岩、白云岩、泥岩、泥质白云岩,渗透系数测定结果显示：第四系黏土层、白云岩、泥岩、泥质白云岩渗透系数数量级分别为10^-6、10^-2-10^-3、10^-6-10^-7、10^-4-10^-5cm/s。其中第四系黏土层和泥岩隔水性能良好,钻探资料显示：第四系黏土层和下伏第一层泥岩局部缺失,不具有隔水效果;第二层泥岩连续分布,且最小厚度大于1 m,渗透系数数量级在5.73×10^-7-1.98×10^-6cm/s,构成天然防渗层。利用解析法对这种＂孤岛式＂多层次地质结构场地污染物垂向渗入地下水水位以下的时间和渗透比例进行了计算分析,作为一种定量的计算结果,在场地地下水防污性能评价中具有指示意义。评价结果显示：污染物垂向渗透时间最小为3 086 d,渗透比例为0.37%,显示地下水防污性能极强。考虑到西南岩溶地区地下水入渗的特点,这种＂孤岛式＂多层次地质结构可作为一种保护地下水资源的模式,在以后工程建设选址中推广。

Based on the drilling data, aeration zone structure is top-down followed by quaternary clay, dolostone, mudstone, dolostone, mudstone, argillaceous dolomite course pack, and permeability test results indicate that hydraulic conductivity of each layer in aeration zone is in the range of 10 ^-6,10^-2 -10^-3,10^-6-10^-7,10^-4-10^-5 cm/s, among which the quaternary clay and mudstone have good water resistance. The second mudstone underlying has continuous distribution, with the minimum thickness more than 1 m and the permeability coefficient of magnitude in 5.73×10^-7-1.98×10^-6 cm/s, which constitute a natural barrier layer. The layer permeability was analyzed by analytical method, and based on the analysis of water balance to the proportion evaluation of the vadose zone water seeping into groundwater, results showed that penetration to the groundwater level is 0.37%, and vadose zone water 99.63% to spring discharge and did not enter into the groundwater level. Considering the groundwater infiltration characteristics in karst region of southwest China, multi-level geological structure can be used as a protection of groundwater resource mode.