Study on the improvement of soil properties using hydrophilic-hydrophobic biopolymer crosslinking

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In recent years, biopolymer soil treatment technology has been increasingly applied in the field of geotechnical engineering due to its environmental friendliness. While biopolymers exhibit the capacity to substantially enhance the mechanical properties of soils, their effectiveness, particularly in the case of polysaccharide-based biopolymers, is often influenced by the water, thereby restricting their practical application in engineering contexts. This study explores the potential of hydrophilic-hydrophobic biopolymer crosslinking, namely xanthan gum and casein, to enhance the strength and water stability of soils. Through a comprehensive array of assessments encompassing unconfined compressive strength (UCS) tests, soaking tests, scanning electron microscopy (SEM) observations, and Fourier transform infrared spectroscopy (FTIR) analyses, the improvement effect, optimal conditions and microscopic mechanisms of the soil treated with hydrophilic-hydrophobic biopolymer crosslinking were investigated. The results demonstrate that compared to the sole utilization of either xanthan gum or casein, xanthan gum-casein crosslinking treatment not only significantly improves the unconfined compressive strength of the soil but also enhances its water resistance. Under optimal treatment conditions, the residual rate of unconfined compressive strength can still maintain a relatively large value after soaking for 24 h, while the soil under other conditions completely disintegrated. Moreover, the hydrophilic-hydrophobic biopolymer crosslinking transforms the gel morphology into an elongated fibrous structure that wraps and surrounds the soil particles to form a cohesive and unified entity, this synergetic interaction further enhances the efficacy of the crosslinking treatment.