Xanthan gum biopolymers have gained increasing attention in geotechnical engineering due to the effectiveness and environmental-friendliness, and are proposed as a potential alternative to conventional materials for soil stabilization. Cyclic wetting and drying are the crucial factors that affect the behavior of surface soil, which are also a major challenge for biopolymer applications. This study aims to investigate the strength durability of xanthan gum-treated soil during wetting–drying cycles. The soil was treated with different contents of xanthan gum (0, 0.5, 1.5% by the mass of dry soil) and a total of 12 wetting–drying cycles were applied. Unconfined compression tests were performed to evaluate the changes in soil mechanical properties. The changes in microstructure were observed using nuclear magnetic resonance technology and scanning electrical microscopy. The results showed that soil mechanical properties decreased significantly in the first four cycles, and then tended to equilibrium. The compressive strength of soil treated with 1.5% xanthan gum could be approximately twice than that of non-treated soil after 12 cycles, and its strength reduction caused by wetting–drying cycling is about 20% less than that of the latter. When increasing the water content at drying stage, specimens subjected to wetting–drying cycles with less moisture change presented higher compressive strength, in which case the effectiveness of biopolymer treatment can be maximally retained. Xanthan gum treatment conferred great resistance to wetting–drying cycling due to its cementation and aggregation effects. The presence of xanthan gum leads to more inter-aggregate pores with a radius of about 0.1–1 μm and limits the development of macropores. The strengthening effect of xanthan gum depends on direct clay particle–biopolymer interactions and inter-particle connection formed by xanthan gum matrix. From the results, xanthan gum biopolymers can significantly improve the mechanical properties of soil at shallow depth even after wetting–drying cycles.

黄原胶生物聚合物由于其有效性和环境友好性而在岩土工程中受到越来越多的关注，并被提议作为传统土壤稳定材料的潜在替代品。循环润湿和干燥是影响表层土壤行为的关键因素，这也是生物聚合物应用的主要挑战。本研究旨在研究黄原胶处理过的土壤在干湿循环过程中的强度耐久性。用不同含量的黄原胶（干土质量的0%、0.5%、1.5%）处理土壤，并总共进行12次干湿循环。进行无侧限压缩试验来评估土壤力学特性的变化。利用核磁共振技术和扫描电镜观察微观结构的变化。结果表明，前4个周期土体力学性质显着下降，随后趋于平衡。经1.5%黄原胶处理的土体经过12个循环后，抗压强度可比未处理的土体提高约2倍，且干湿循环引起的强度降低比后者减少约20%。当干燥阶段的含水量增加时，经过湿干循环且水分变化较小的样品表现出较高的抗压强度，在这种情况下可以最大程度地保留生物聚合物处理的有效性。由于其胶结和聚集效应，黄原胶处理赋予了对干湿循环的极大抵抗力。黄原胶的存在导致更多的聚集体间孔隙，半径约为0.1-1μm，并限制了大孔隙的发展。黄原胶的增强效果取决于粘土颗粒与生物聚合物的直接相互作用以及黄原胶基质形成的颗粒间连接。从结果来看，即使在干湿循环之后，黄原胶生物聚合物也可以显着改善浅层土壤的力学性能。