雨洪水回灌过程中堵塞滤层特征试验

Characteristics of mechanical clogging in rain-flood infiltration system

采用室内砂柱试验模拟雨洪水回灌条件下含水层的堵塞过程,通过测定堵塞层的渗透系数和渗滤速率的变化分析回灌过程中的物理堵塞特征。试验结果显示,在回灌后36h,砂柱上部(25～40cm)的渗透系数明显减小,由初始的6.58m/d减小到3.72m/d,而中下部(40～70cm)的渗透系数变化很小,由初始的6.45m/d减小到5.25m/d;比较悬浮物质量浓度分别为50mg/L,100mg/L,200mg/L和400mg/L的回灌水回灌过程表明,悬浮物质量浓度越高,砂层的渗透速率下降越快;对比分析回灌前后的悬浮物颗分结果表明,回灌后的悬浮物(砂层表部淤泥层)出现细化现象;回灌过程中在砂柱表面形成的淤泥层和砂层上部的淤堵是整个含水层堵塞失效的主要原因。

The mechanical clogging process of aquifer under rain-flood infiltration was simulated by means of the laboratory tests on sand columns.The characteristics of mechanical clogging were analyzed by measuring the variations of permeability coefficient and infiltration rate of the clogging layer during the infiltration process.The test results show that 36 h after the infiltration,the permeability coefficient at the upper part（25-40 cm） of the sand column significantly decreases,from the initial 6.58 m/d to 3.72 m/d,and that at the middle and lower parts（40-70 cm） has small change,from the initial 6.45 m/d to 5.25 m/d.A comparison among the processes of infiltrated water with concentrations of suspended sediment of 50,100,200 and 400 mg/L indicates that the higher the concentration,the faster the decrease of the infiltration rate of silt layer.A comparison of the grain sizes of suspended sediment before and after infiltration shows that the grain size of suspended sediment（surface muddy layer of the silt layer） appears fine phenomenon after infiltration.The muddy layer formed on the surface of the sand columns and the clogging at the upper part of the silt layer during the infiltration process are the main causes for the clogging failure of the whole aquifer.