荆南长江干堤堤基防渗加固措施

讨论荆南长江干堤堤身的土质状况,对堤基土层结构进行分类,通过渗流计算提出荆南长江干堤典型断面堤基防渗加固处理措施。针对荆南长江干堤堤基土层结构的特点,提出堤基防渗加固处理的原则:堤防防渗加固方案的选择必须顾及堤基土体的物理力学性质,以及堤基周围的人文及地理环境要素,同时应考虑到用于堤防加固处理的经费,通过多种方案的比较,找出其中最合理的方案;当透水层上的覆盖层较薄且透水层较厚时,应采用盖重的方法进行堤基防渗处理,必要时增加排渗井或减压沟,以增强堤基的防渗效果;当透水层较薄且透水层下为基岩或有较厚的相对弱透水层时,可采用全封闭式防渗墙或半封闭式防渗墙进行堤基防渗;若透水层特别薄且透水层的颗粒较细时可采用土工膜进行堤基防渗,以节约堤基防渗的成本。

Measures for seepage control and reinforcement of Jinnan dike foundation on Yangtze River

The soil condition of the dike body was discussed,and the structure of soil layer of the dike foundation was classified.Then,the measures for seepage control and reinforcement of the dike foundation for some typical cross-sections of Jinnan dike were proposed by means of seepage calculation.In consideration of the characteristics of soil layer structure of the dike foundation,the principle of seepage control and reinforcement of dike foundation was put forward: the physical-mechanical properties of soil mass of the dike foundation and the cultural and geological environment factors around the dike foundation as well as the cost should be taken into account in selection of the schemes for seepage control and reinforcement of the dike,then the optimal scheme should be determined by comparison of various schemes.Some conclusions are drawn as follows: if the covering layer on the pervious layer is thin while the pervious layer is thick,the heavy coverage method should be taken,and dewatering wells or decompression ditches may be added if it is necessary so that the effect of seepage control could be enhanced;if the pervious layer is relatively thin with bed rock and thick but weak pervious layer below,the fully-closed or semi-closed impervious walls should be taken for seepage control of the dike foundation; if the pervious layer is especially thin with fine grains,the geomembrane should be taken for seepage control so that the cost for seepage control could be reduced.