Shear behavior and predictive modeling of loess stabilized with rice husk ash

This study explores the utilization of rice husk ash (RHA), an agricultural waste byproduct, as an eco-friendly stabilizing agent to address the high compressibility and water sensitivity of loess soils. A series of laboratory tests and microstructural analyses were conducted to investigate the shear behavior of RHA-modified loess, and a predictive model for its shear strength was developed. The results indicate that as the RHA content increases, the maximum dry density of the stabilized loess decreases, while the optimum moisture content (OMC) rises. At an optimal RHA content of 10%, the modified loess achieves peak mechanical performance: shear strength increases by 46.41–49.36%, cohesion improves by 36.3%, and the internal friction angle rises by 46.7%. Microstructural analysis reveals that the porosity of the modified loess decreases by 21.8% compared to untreated loess. However, shear strength diminishes significantly with increasing moisture content, exhibiting a maximum reduction of 80.5% at 1.6 OMC, with high confining pressure exacerbating this weakening effect. Furthermore, based on experimental data, a predictive model for the shear strength of modified loess, incorporating moisture content and compaction effects, was established. A modified Coulomb–Mohr criterion accounting for moisture content and confining pressure was also derived.