不同饱和黏性土渗透系数预测方法的应用与对比:以苏北沿海平原黏土为例

渗透系数(K)是水文地质、岩土工程领域的重要参数，而低渗透介质的结构较为复杂，在实际应用中，场地的尺度、介质的扰动程度等均会对K的确定产生影响.利用δ18O化学示踪法、室内试验及经验公式法估算饱和黏性土的垂向渗透系数，并对比分析不同预测方法的适用性.以苏北沿海平原第四纪厚层黏土为例，δ18O化学示踪法预测厚层黏性土的渗透系数低于10-11 m/s，室内法测得渗透系数为2.61×10-8~9×10-12 m/s，经验法预测值较大，是室内法的几倍到几十倍.δ18O化学示踪法是表征天然条件下长时间的实验结果，除了反映数十米厚层黏性土的等效渗透性能，还可预测黏土孔隙水的渗流时间；结合测定黏土样品液塑限等室内实验参数，室内实验和经验公式法可以提供系列剖面黏土的渗透系数，更清晰地说明厚层黏土剖面不同渗透系数预测方法的差异性. 

Application and Comparison of Various Methods for Determining Hydraulic Conductivity in Saturated Clay-Rich Deposits—A Case Study of Clay-Rich Sediments in North Jiangsu Coastal Plain

The hydraulic conductivity (K) of deposits is one of the important and fundamental properties for solving various problems in the study filed of hydrogeology and geotechenical engineering. However, in the study of clay-rich deposits, the selection of the evaluation method for K is obviously affected by the scale of the site and the degree of deposits disturbance due to the complex deposit structure. Chemical (δ18O as the tracer), laboratory, and empirical formula methods were used to predict the vertical hydraulic conductivity in saturated clay-rich deposits, and their practicability was analyzed. Take the Quaternary thick clay-rich sediments in North Jiangsu coastal plain for example, the estimated hydraulic conductivity of the thick clay-rich sediments was lower than 1×10-11 m/s using δ18O chemical methods. Using laboratory method, that range between 2.61×10-8 and 9×10-12 m/s. The larger predictive values were determined by empirical formula method and higher than that obtained using hydraulic method by several times. Chemical method was applied to display the long-term experimental results under the natural conditions, and the equivalent permeability of the decade meters clay-rich deposits. Besides, the residence time of pore water in the sediments was also predicted. Combined with the laboratory parameters of clay samples, such as liquid and plastic limit, laboratory and empirical formula methods could provide series hydraulic conductivities of the whole profile, in order to show the difference of different permeability coefficient prediction methods in thick clay-rich profile.