王家营险工险段地质环境与历次溃口险情

汉江遥堤为国家Ⅰ级堤防，遥堤王家营险工险段堤身填筑修筑时间跨度大，土体成分复杂。堤基地质结构为典型的“上砂下粘”双层结构，地表直接出露粉细砂。渗透变形试验表明，王家营粉细砂临界比降和破坏比降比其它长江重要堤防同类土小，渗径短，水力比降大，容易产生渗透破坏。建议对堤基和堤身进行垂直防渗处理，处理深度入粘性土2m为宜。

Geological Environment of Wangjiaying Dangerous Reaches and Its many Dam Breaks

Hanjiang distant dyke is the national grade one dyke.On the Wangjiaying dangerous reaches, the dyke body has been built over a long period of time .Its earth formation is complicated.The geological structure of the dyke base is typical of double layer with sand on the top and clay on the bottom.Seepage test shows that the ratio of critical gradient of fine sand to destruction gradient is smaller than that of the other important dyke, The seepage paths are short and hydraulic gradient is great, which easily pruduces seepage destruction. So, both the dyke base and the dyke body should be treated vertically with seepage control.The treatment should be two meters deep into the clay.