Regulatory effects of attapulgite on water transport in wind-sandy soil: Soil column tests and numerical simulations

Attapulgite (ATP), a natural inorganic material, has significant potential for use in the regulation of water transport in aeolian sandy soils. In this study, indoor soil column tests and numerical simulation studies were performed with different parameters (including the percentage of ATP blended, the surface blending thickness, the interlayer thickness, and the profile reconstruction method). The regulatory effects of ATP addition on the infiltration and evaporation processes occurring in aeolian sandy soil were explored, and an XGBoost prediction model was constructed. The key influencing factors and their interactions were analyzed using the SHAP method. The addition of ATP could effectively delay the infiltration rate and inhibit the evaporation process, with 8% blending achieving the optimal water-holding effect. There were significant differences in effective water content, wet front advancement time, and evaporation inhibition between the 2% and 10% blending treatments, confirming that the regulatory effects were dependent on the applied dosage. Under different profile configurations, T1 treatment (10 cm surface blending+10 cm deep interlayer) simultaneously optimized both seepage reduction and evaporation suppression. The XGBoost model demonstrated excellent accuracy for the prediction of the moist front migration and cumulative infiltration (R2>0.98). The SHAP results indicated that the cumulative volume of infiltration, the time, and the saturated water content were the main driving factors. The findings of this research provide supporting data and technical methodology for the rational application of ATP to improve water retention in wind-sandy soil.