Influence of constriction-based retention ratio on suffusion in double-layered alluvial foundation with a cutoff wall

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.