Improving surcharge capacity and reducing displacement of clay slopes using biostimulated microbially induced calcite precipitation

Abstract

Roads, embankments, and buildings in contoured areas are often constructed on clay slopes. Their stability becomes a critical concern especially under additional surcharge loads. This research investigates the effectiveness of biostimulated Microbially Induced Calcite Precipitation (MICP) in improving surcharge capacity and reducing displacement of clay slopes. Physical slope models with inclinations of 60° and 70° were prepared using air pluviation and layering techniques, incubated for 7, 14, and 28 days, then tested under controlled vertical loading. Samples were also subjected to direct shear test, SEM-EDX microstructural, and ANOVA. The results showed that the most significant mechanical improvement was observed after 14 days of incubation, with an increase in surcharge capacity of 83.31% for the 60° slope and 103.45% for the 70° slope. The treated slopes exhibited reduced displacements with stiffer responses and delayed plastic deformation compared to the untreated slopes. The improvement was primarily associated with increased cohesion resulting from calcite bonding at interparticle contacts, whereas the internal friction angle showed moderate and relatively sTable gains at extended incubation. Microstructural observations confirmed localized CaCO3 precipitation concentrated in specific zones. Statistical analysis (p < 0.05) verified that the observed mechanical improvements were attributable to the MICP treatment. These findings indicate that biostimulated MICP effectively reinforces clay slopes by enhancing shear strength parameters and suppressing deformation under surcharge loading. Increased slope stability allows steeper slope angles, enabling more optimal land utilization above the slope