悬挂式防渗墙防渗效果的模拟试验研究

RESEARCH ON EFFECT OF SUSPENDED CUT-OFF WALL WITH SIMULATION TEST

在实验室渗流槽中进行有悬挂式防渗墙的二元结构堤基的渗流模拟试验,取得不同贯入度悬挂式防渗墙防渗效果的系列试验成果。论证悬挂式防渗墙对上层为低液限黏土、下层为低液限粉土的二元堤基在发生渗透变形时有阻滞渗透变形发展的重要作用。对于上部为粉质黏土,下部为粉土的二元结构堤基,发生渗透变形时首先在粉土层的薄弱部位发生涌砂,接着在粉质黏土层与粉土层的结合层面发生接触冲刷,在水位持续升高到超过临界水位后,渗透通道从下游向上游发展而贯通,即发生渗透破坏。同时,研究发现,在悬挂式防渗墙作用下,堤基土发生渗透破坏的条件有明显改善,表现在渗透破坏时的作用水头有较大的增长,临界表观水力梯度有明显提高,渗流量显著减小,孔隙水压力分布发生变化。研究结果表明,悬挂式防渗墙可以有效控制渗透破坏的发生条件,而且施工相对容易,也比较经济合理,可以在工程中推广应用。

The model test for simulating effect of suspended cut-off wall on preventing seepage failure in two-layer foundation of levee has been carried out in a sandbox. The experimental results for different suspension depths have been obtained. The results indicate that the suspended cut-off wall has significant effects on the prevention of seepage failure as well as reduction of seepage quantity in two-layer foundation of levee which is composed of upper clay and lower silt soil during the stability seepage. For the two-layer foundation of levee,sand spring occurs at the weak positions,then contact erosion occurs at the interface of silt clay and silt. When the water level rises continuously and exceeds the critical water level,the seepage channel develops from downstream to upstream,and runs through the whole soil. At this time,the seepage failure occurs. Research indicates that,under the function of suspended cut-off wall,the condition that seepage failure occurs has been improved,for example,the water level rises greatly,critical apparent hydraulic gradient increases obviously,the seepage quantity reduces distinctly,and the pore water pressure changes evidently. The results show that the suspended cut-off wall can prevent the seepage failure effectively,at the same time,it is constructed easily and acceptable in economy,so it is worth applying in project.