Sustainable stabilization of expansive soils for slope applications using enzyme-induced carbonate precipitation and iron ore tailings

Expansive soils exhibit pronounced swelling-shrinkage behavior, low shear strength, and high moisture sensitivity, posing significant challenges to the stability of geotechnical structures such as embankments and tailings dam slopes. In this study, a sustainable stabilization strategy integrating enzyme-induced carbonate precipitation (EICP) with iron ore tailings is investigated to improve the hydro-mechanical performance of expansive soils. A comprehensive experimental program was conducted to evaluate changes in unconfined compressive strength (UCS), swelling pressure (Ps), hydraulic conductivity (Ks), cohesion (c), and internal friction angle (φ). Microstructural characterization using scanning electron microscopy and X-ray diffraction was performed to examine calcium carbonate precipitation and its cementation effects within the soil matrix. The results demonstrate that the combined EICP-iron ore tailings treatment significantly enhances soil performance, with UCS, c, and φ increasing by approximately 113%, 48%, and 98%, respectively, while Ps and Ks decrease by approximately 98% and 69%. Furthermore, seepage and slope stability analysis using GeoStudio (SEEP/W and SLOPE/W) indicate that the stabilized soil achieves a markedly higher factor of safety (FoS = 1.896) compared to untreated soils. The findings confirm that the synergistic integration of EICP and iron ore tailings provides an effective, environmentally sustainable, and engineering-feasible solution for stabilizing expansive soils and improving slope performance in tailings dam applications.