由于膨胀土对于水的敏感性,膨胀土渠坡及其衬砌结构的稳定性是南水北调中线一期工程建设和运行遇到的重要挑战之一。在地层结构分类基础上,开展了膨胀土地区的渗透结构分类、渗流系统分类以及膨胀土渠坡渗流系统分类研究。针对各类膨胀土渠坡渗流系统,分析了渠道工程对渗流场的改造作用,归纳了各自的渗流控制任务,提出了渗流控制措施的应用原则:非饱和带设置排水垫层以利于含水率的长效控制,合理设计马道以减轻对渗流控制的负效应,合理运用排水孔和减压井控制地下水流场及水压力,地下水动态变化与渠道水位变化范围交叉渠段应合理设置逆止阀并保障其灵敏性和可靠性,工程长期运行过程中跟踪研究渗流控制效果和适时有效调控渗流场。

Because expansive soil is very sensitive to water,the stability of expansive soil slope and its lining structure is one of the important challenges for the construction and operation of the first-stage project of middle route South-to-North Water Diversion in China. On the basis of geological structure classification, the permeability structure and seepage field system in expansive soil area and also the seepage field system in expansive soil slope of canal were classified respectively. For different kinds of seepage field system in expansive soil slope of canal, the seepage field transformations caused by canal construction were analyzed. The main tasks for seepage field control were discussed, and the principle was pointed out for the application of seepage field control scheme: laying drainage liner for long-term control of water content in unsaturated slope, deliberate design of berms with their negative effects on seepage control considered, reasonable utilization of drainage holes and relief wells to control seepage field and ground water pressure, reasonable arrangement of sensitive and reliable check valves for the canal stretches with the variation range of ground water level overlapping that of canal water level, tracking research on the efficiency of seepage field control and timely regulating it effectively.