Enhancing clay soil reinforcement using the MICP-BIN method with biochar-induced nucleation

Abstract

The microbially induced carbonate precipitation (MICP) method has gained extensive use in the realm of soil stabilization. The combination of MICP with biochar offers potential benefits in terms of simultaneous strength enhancement and vegetation cover enhancement. This study presents a novel microbial solidification technique known as the biochar-induced nucleation (MICP-BIN) method for reinforcing clay soil. Corn stover biochar was employed as an auxiliary material, mixed with dry clay powder, and subsequently reinforced using the MICP technique. Direct shear tests (DSTs), drying experiments, X-ray diffraction (XRD), and scanning electron microscopy (SEM) were also conducted to investigate the efficacy of the MICP-BIN method. Compared with that of the remolded soil, the shear strength of the treated soil exhibited a substantial increase of 22.4%, the CaCO3 content increased by 30%, and the shear strength improved by 389.5%. Similarly, the internal friction angle exhibited increases of 22.7% and 405.2%, while the cohesion showed improvements of 9.4% and 344.3%, respectively. The MICP-BIN method is found to increase suction for a given water content. Further, biochar amended soil possesses highest water retention ability (especially at lower suction magnitude) followed by MICP amended soil, MICP-BIN amended soil and untreated soil. The difference in water retention abilities among various soils is negligible at higher suction magnitude. Further, there is no significant change in air entry value of MICP-BIN amended soil as compared to the untreated soil and MICP amended soil. This study demonstrated the promising results achieved by combining biochar and the MICP-BIN technique, providing a novel approach for reinforcing soft ground.