Experimental study on influence of xanthan gum content on strength and deformation characteristics of regetated loess

To address the engineering issues of weakened cementation and collapsibility sensitivity in typical structured loess from Northwest China, this study uses Yangling loess as the research subject and systematically investigates the macro- and micro-mechanisms of the xanthan gum-bamboo fibril composite system in improving Yangling loess through laboratory tests (unconfined compressive strength tests and direct shear tests) and microscopic analysis (SEM), analyzing the influence of xanthan gum content on the strength and deformation characteristics of vegetated loess. The experimental results indicate that: When bamboo fibril is solely incorporated, the unconfined compressive strength (UCS) of vegetated loess (formed by loess and bamboo fibril) increases with higher fiber content and longer curing periods, while showing an initial increase followed by a trend of decrease with increasing fiber length. The optimal parameters for bamboo fibril incorporation into loess are 9 mm length, 0.8% content, and a 28-day curing period. After adding xanthan gum, the UCS of vegetated loess increases with extended curing time, while the UCS, shear strength, cohesion, and internal friction angle first increase and then decrease with increasing xanthan gum content. The optimal parameters for xanthan gum in vegetated loess are 0.75% content and a 28-day curing period. SEM analysis demonstrates that bamboo fibril acts synergistically with xanthan gum films to bridge cracks, forming reinforced transition layers at fiber-soil interfaces and constructing a "rigid skeleton-flexible cementation" composite system, thereby significantly enhancing the mechanical properties of loess.