Effects of Repetitive Loading on Deformation and Shear Wave Velocity of Xanthan Gum-Treated Soils

Biopolymers have recently attracted attention as eco-friendly soil stabilizers that can be effectively applied to geotechnical structures subjected to repetitive loading, such as railway subgrades and highways. This study evaluated the influence of xanthan gum biopolymer on the deformation behavior and shear wave velocity of sand-biopolymer mixtures. Laboratory tests were performed by mixing sand with various xanthan gum contents (0, 0.5, 1, 2, 5, and 10%) while maintaining a relative density of 50% and degree of saturation of 30%. Settlement was continuously monitored using an linear variable differentialA transformer during repetitive loading, and shear wave velocity was measured at four stages: immediately after specimen preparation, after curing, and following repetitive loading under static vertical stresses of 50 and 200 kPa. The results indicated that final deformation converged in specimens with higher biopolymer contents (BPC 5.0 and BPC 10.0), suggesting stabilization at the deformation limit. In addition, the highest shear wave velocity was observed at an optimal content of 0.5-1.0%, reflecting increased stiffness due to biopolymer-soil bonding. These findings highlight the significant potential of xanthan gum as a sustainable soil reinforcement material. Determining its optimal content is critical for improving soil stiffness and reducing deformation under repeated loading conditions.