Backward erosion piping through vertically layered soils

Abstract

Backward erosion piping is an important failure mechanism for water-retaining structures, a phenomenon that results in the formation of shallow pipes at the interface of a sandy foundation and a cohesive cover layer. This paper studies the effect of two sand types on backward erosion piping; both in case of a homogeneous sand layer, and in a vertically layered sand sample, where the pipe is forced to subsequently grow through the different layers. Two configurations with vertical sand layers are tested; they both result in wider pipes and higher critical hydraulic gradients, thereby making this an interesting topic in research on measures to prevent backward erosion piping failures. Grain size analysis shows that the finer fraction is more likely to be eroded and also indicates that grains usually do not settle once they are eroded.