The Relationship between Biopolymer Concentration and the Erodibility of Coarse-Grained Soil Comparing Tests Performed Using Different Boundary Conditions

The objective of this paper is to examine the relationship between biopolymer concentration and the erodibility of coarse-grained soil. The erosion of soil by water (referred to as scour) is an important issue that affects many engineering structures such as earthen dams, levees, bridges, and embankments. Scour is one of leading causes of bridge failure; the cost of repairs due to scour has reported by the United States Department of Transportation to be very high. This gives rise to the need for an environmentally friendly solution to improving soil supporting these structures. Biopolymers, naturally occurring polymers that are found in living organisms, have been seen as a viable solution for ground improvement. Biopolymer treatment has been shown to enhance soil properties such as shear strength, compressive strength, and friction angle. Greater resistance to erosion is expected in samples treated with biopolymers. To confirm the erodibility of treated samples, this study will use the erosion function apparatus (EFA) to quantify the erosion rate of soil specimens with varying biopolymer concentrations. Xanthan gum was the biopolymer used to treat the soil specimens at 0.2%, and 0.4% concentration by weight of the soil. Well-graded Acco sand was used for this experiment. During the experiment, erosion rates were measured for each soil specimen in the EFA at the same velocity. Specimens were not allowed to cure for more than 1 h before testing and were prepared with the same water content and relative density. In this paper, comparisons are made between the tests performed in preliminary experiments in a different flume and those performed in the EFA.