Erosion Characteristics of Silty to Clayey Soils Using EFA and Lab-Scaled Levee-Floodwall Tests

Abstract

The erodibility of levee material has an influence on scour generation in levee-floodwall systems. In this investigation, the effect of various soil parameters including compaction level, plasticity index, and saturation ratio on erosion rates was studied using two methods: lab-scaled physical models of levee-floodwall systems and the Erosion Function Apparatus (EFA). For physical models, a 1:20 scale of a typical levee on the banks of the Mississippi river was constructed. The effect of the floodwall and its inclination on levee erosion were investigated. For EFA tests, the soil samples were prepared in the same way as the materials prepared for physical model tests in order to compare the erosion rate characteristics of these methods. EFA test results show that the erosion rate for soils with more than 60 % saturation levels is more sensitive to change in saturation levels than changes in plasticity index or compaction levels. An erosion rate prediction model was developed for various soils using EFA tests. The levee-floodwall tests show that the erosion rates at the crest are significantly more sensitive to soil parameters than at the slope. The erosion rates for levee-floodwall tests are much greater than the ones for EFA tests. Furthermore, the effect of floodwall inclination and presence in levees are discussed.