Cr3+-crosslinked xanthan gum hydrogels for enhancing penetration efficiency and post-installation pullout resistance of bioinspired piles

The use of biopolymer hydrogels for bioinspired piles is emerging as a sustainable approach to enhance penetration efficiency and ensure pile stability after installation. Xanthan gum (XG) hydrogels possess shear-thinning properties, which reduce penetration resistance under high shear strain conditions. However, their limited durability under wet conditions restricts their field application. To address this, this study introduces trivalent chromium (Cr3+) crosslinked XG and investigates the mechanical performance enhancement of treated soils and piles. Rheological tests revealed that both XG and Cr–XG hydrogels exhibited shear-thinning behavior with increasing shear rate, whereas Cr3+ crosslinking significantly increased yield stress and flow point, thereby enhancing structural stability after gelation. Direct and interface shear-test results showed that XG concentration and Cr3+ addition significantly increased cohesion and interface adhesion. Laboratory-scale pile-penetration tests demonstrated that XG-hydrogel injection reduced end bearing and skin friction during penetration, improving installation efficiency. The pile treated with 1.0% Cr–XG exhibited the highest pullout resistance post-installation. These results demonstrate the potential of the Cr–XG 1.0% hydrogel to simultaneously improve penetration efficiency and post-installation stability, presenting a bioinspired strategy for sustainable pile-foundation design.