Characterizing Optimum Water Content of Biopolymer-Treated Sand

Breaching associated with overtopping is a prevalent cause of earthen dam failure that has triggered widespread flood-related damage. Reducing sediment erodibility is critical to mitigate the risk of embankment failure. Traditionally, sediment properties are improved mechanically or chemically. However, chemical additives have drawbacks, such as altering soil properties or introducing toxicity. Recent studies have considered the use of biopolymers, like xanthan gum, to enhance sediment properties with limited adverse effects. While geotechnical tests have shown that biopolymers can bolster soil strength, biopolymer impacts on soil erodibility and resistance in real-world conditions remain uncertain. Experiments are in progress at the University of South Carolina Hydraulics Laboratory to investigate erodibility of xanthan gum-treated sand and its relation to flow velocity. Factors examined include optimum water content, biopolymer concentration, average flow velocity, and erosion rate. This paper presents results describing how optimum water content varies with silt and gum content. In particular, optimum water content of sand-xanthan gum mixtures increases with biopolymer concentration. In sand-silt mixtures, optimum water content is highest, and it does not vary with xanthan gum concentration.