Investigations on Fully Softened Strength of Lime-Treated Slopes Built with Expansive Soils under Future Extreme Precipitation

Highway slopes built with expansive soils are often prone to surficial slope failures due to volumetric fluctuations from cyclic ingress and egress of moisture arising from repeated wet-dry weathering cycles. This periodic shrink-swell phenomenon may result in the formation of desiccation cracks, which result in the transition of strength from peak to fully softened and subsequently result in surficial slope failures. Calcium-based stabilizers such as lime are often used to negate the effects of high-plastic clay by enhancing strength and subsequently reducing volumetric strains. However, cyclic wetting and drying can often impact the long-term serviceability of such treated slopes. A research study was conducted to understand the efficacy of different lime dosages against surficial slope failures. Laboratory studies were performed on untreated, 5%, and 8% lime-treated soils at two different curing periods to estimate the changes in peak and fully softened shear strengths. Rainfall-induced slope stability analyses were performed on a hypothetical slope considering the effects of future precipitation in Texas and determining the stability of lime-treated surficial slope. Preliminary studies indicate that lime treatment improves the fully softened strength, and a unique relation exists between the treated soil plasticity and the secant friction angle values. Stability analyses indicated that the lime-treated slopes are less prone to degradation from repeated wet-dry cycles due to the formation of a hydrophobic and resilient soil matrix. Overall, the study provides a comprehensive insight into chemically stabilized surficial slope failures and the effects of environmental changes on the serviceability of this transportation infrastructure.