Abstract This paper presents a series of flume-scale tests to investigate suffusion near the tip of a cutoff wall in a double-layered alluvial foundation, where the upper and lower soil layers serve as filter and base soil, respectively. A constriction-based retention ratio was adopted to describle the particle size ratio between the two layers. The results indicate that the upper soil layer significantly influences the evolution of suffusion in the double-layered foundation soil. Suffusion initiates near the tip of the cutoff wall or at its upstream side, then it progresses forward to the downstream side. Meanwhile, the upper soil layer has a remarkable influence on the critical hydraulic gradients at the initiation of suffusion and at blowout. The critical hydraulic gradients exponentially decrease with the increase of constriction-based retention ratio. If the constriction-based retention ratio is less than 1, the upper soil layer significantly increases the critical hydraulic gradients. If the constriction-based retention ratio is larger than 1, it slightly increases the critical hydraulic gradients.

中文翻译：

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带截流墙的双层冲积地基中缩窄留水率对渗流的影响

摘要 本文提出了一系列水槽尺度试验来研究双层冲积地基中截流墙尖端附近的溢流，其中上层和下层土层分别作为过滤土和基土。采用基于收缩的保留比来描述两层之间的粒度比。结果表明，上层土层显着影响双层地基土中的扩散演化。溢流在截止壁的尖端附近或其上游侧开始，然后向前推进到下游侧。同时，上层土层对渗流开始和井喷时的临界水力梯度有显着影响。临界水力梯度随着基于收缩的保留率的增加呈指数下降。如果基于收缩的保留比小于 1，上层土层会显着增加临界水力梯度。如果基于收缩的保留率大于 1，则会略微增加临界水力梯度。