Analysis of strength characteristics of EICP-treated earthen site soil considering matric suction effects

This study aimed to elucidate the mechanisms of hydraulic erosion degradation in Enzyme-Induced Calcium Carbonate Precipitation (EICP)-treated earthen site soil, with a specific focus on the Zhouqiao earthen site in Kaifeng. After conducting dry-wet (DW) cycles, tests were performed on matric suction, shear strength, scanning electron microscopy (SEM), and mercury intrusion porosimetry (MIP) on the improved soils at various concentrations of cementation solution (CS) ranging from 0 to 1.5 mol/L. Changes in hydraulic and strength properties before and after the DW cycles were measured. Detailed SEM and MIP analyses comparing microstructural evolution at different CS concentrations indicated that as CS concentration increases, matric suction, internal friction angle, cohesion, and shear strength initially rise and subsequently decline, with optimal performance observed at 1.0 mol/L. Based on the microanalytical data, we propose a model that describes the interaction among the calcium carbonate, water, and soil particle phases. Furthermore, using a modified Moore–Cullen model that incorporates the effects of matric suction, we propose a mechanism for strength deterioration in EICP-treated soils under varying water content conditions.