Influence of Xanthan Gum on Compaction and Shear Strength Behavior of Kaolinite and Loess

Earthen dams and embankments play a crucial role in flood protection and are highly vulnerable to structural failures due to various environmental and operational factors. These structures are composed of soils with varying shear strength and compaction characteristics depending on the mineralogy and moisture conditions of the site. Prolonged exposure to various environmental conditions can weaken the levee structure, increasing the risk of failure. These levees are usually characterized by fine-grained soils like kaolinite and loess, which behave differently under various environmental loads and stabilization techniques. This study investigates the potential of xanthan gum, a natural biopolymer, as a soil stabilization agent to improve the shear strength and deformation behavior of embankment soils under varying moisture and stress conditions. To evaluate the effectiveness of xanthan gum, untreated soil samples and treated soil samples with 2% xanthan gum were prepared and compacted at optimum, dry of optimum, and wet of optimum. The compacted samples were then subjected to direct shear testing under normal stresses of 50 kPa, 250 kPa, and 350 kPa to evaluate the influence of the treatment, compaction level, and normal stress on the peak strength characteristics of kaolinite and loess. Xanthan gum treatment resulted in a reduction in the maximum dry unit weight and an increase in the optimum moisture content in both soils, with a more significant impact in loess due to its low plasticity and coarse texture. In terms of mechanical performance, xanthan gum treated samples showed higher peak shear strength compared to untreated samples, particularly when compacted at optimum or wet of optimum. Kaolinite resulted in higher compressibility and vertical strain when treated with xanthan gum, whereas loess exhibited a stiffer and less deformable response with treatment.