Mechanisms of crack evolution and shear strength degradation in biopolymer-stabilized slurry soils under Dry–Wet cycling

Abstract

Biopolymers are environmentally friendly alternatives to conventional soil stabilizers, yet the response of stabilized slurry soils to repeated dry–wet cycling, particularly crack evolution and associated strength degradation, remains insufficiently understood. To address this gap, this study evaluated slurry soils treated with xanthan gum (XG), sodium alginate (SA), and cationic guar gum (CGG) using mass loss measurements, quantitative crack analysis, direct shear tests, and scanning electron microscopy. Among the three biopolymers, XG exhibited the best performance at a dosage of 1.5%. After eight cycles, XG-treated soil exhibited a mass loss of 1.62%, 79.3% lower than that of untreated soil, while maintaining a crack ratio below 1.9% and an average crack width of 0.222 mm. It also retained approximately 70% of its initial shear strength, compared with 65% for CGG, 57% for SA, and 53% for untreated soil. Strength degradation was primarily associated with cohesion loss and progressive crack development. Microstructural observations showed that XG formed a relatively continuous polymer network that enhanced particle bonding and structural integrity, whereas CGG produced localized bonding and SA exhibited a less continuous structure. Overall, these results identify XG as the most effective biopolymer investigated and demonstrate its potential for improving the long-term durability of slurry soils under cyclic moisture conditions.