Research on the Improvement of Water Retention, Anti-Erosion and Mechanical Properties of Aeolian Sand Slopes Under the Synergistic Effect of Xanthan Gum and Water Retention Agents

Aeolian sand slopes in the Fugu area of Yulin, Shaanxi Province, China, are prone to rainfall-induced erosion because of the loose structure and low water-holding capacity of the sand, which constrains long-term, sustainable ecological restoration. To address this, aeolian sand was amended with xanthan gum (XG) and a superabsorbent polymer (SAP) and combined with a honeycomb confinement system; evaporation, 70 mm·h−1 rainfall–erosion, and direct shear tests were carried out. SAP increased the 24 h water content of untreated sand from 1.8% to about 20–22%, while excessive SAP led to surface cracking. XG strengthened interparticle bonding and reduced 60 min cumulative erosion from about 53 kg to <0.5 kg (reduction > 99%) and improved shear strength. Within the practically recommended range (XG 0.5–1.0%, SAP ≤ 0.25%), XG and SAP showed water-supply-improving and surface-strengthening effects that effectively covered the early-stage vegetation protection gap, i.e., the period before vegetation becomes dense enough to resist raindrop impact and runoff erosion. The results provide laboratory support for sustainable, nature-based stabilization of aeolian sand slopes in semi-arid engineering areas.