为探究黄原胶对全风化膏溶角砾岩重塑土的改良效果及加固机理，通过液塑限试验和直剪试验分析不同黄原胶掺量下土样的液塑性与强度指标变化规律，确定最优掺量比例。基于三轴试验和电镜扫描试验，进一步研究最优掺量下黄原胶改良土样的力学性能与微观结构特征，揭示其加固机理。结果表明： 1）全风化膏溶角砾岩重塑土呈现面-面叠聚体连接的层状结构，存在明显的裂隙和空洞； 黄原胶通过与土壤细颗粒及水分相互作用，产生键合、胶结、填充和成膜效应，将土颗粒紧密联结，形成不规则晶体填充孔隙，显著增强土颗粒间联结强度，改善土体力学性能。2）黄原胶最优掺量为1.5%，此时改良土样的弹性极限应力与峰值应力增加，峰值应力提升8.0%，呈现明显应变硬化特性，且孔隙水压力随轴向应变均匀缓慢增长，峰值孔隙水压力明显降低，有利于围岩稳定。3）改良土样的有效应力峰值提升11.4%～16.2%，有效黏聚力提高61.8%，总应力内摩擦角增加12.9%，平均弹性模量提升15.5%，强度和刚度均得到显著改善。
To explore the improvement effect and reinforcement mechanism of Xanthan gum on completely weathered residual gypsum breccia remolded soil, liquid-plastic limit and direct shear tests are conducted to examine variations in consistency limits and strength indices of soil samples with varying Xanthan gum contents, thereby determining the optimal mixing ratio. Based on triaxial and scanning electron microscopy tests, the mechanical properties and microstructural characteristics of Xanthan gum-modified soil samples at the optimal mixing ratio are further examined, elucidating the reinforcement mechanism. The results reveal the following: (1) The completely weathered residual gypsum breccia remolded soil exhibits a layered structure with face-to-face aggregated connections, displaying distinct fissures and voids. Xanthan gum interacts with fine soil particles and moisture, generating bonding, cementation, filling, and film-forming effects that tightly connect soil particles. These interactions form irregular crystals that fill pores, remarkably enhancing interparticle bonding strength and soil mechanical properties. (2) The optimal Xanthan gum content is 1.5%, at which modified soil samples demonstrate increased elastic limit stress and peak stress (an 8.0% enhancement), pronounced strain-hardening characteristics, and a uniformly slow increase in pore water pressure with axial strain. The peak pore water pressure notably decreases, benefiting surrounding rock stability. (3) Modified soil samples show an 11.4%－16.2% increase in effective peak stress, a 61.8% increase in effective cohesion, a 12.9% increase in the total stress internal friction angle, and a 15.5% improvement in the average elastic modulus, confirming considerable enhancements in both strength and stiffness.
