Evaluation of the treatment variables on the shear strength of loess treated by microbial induced carbonate precipitation

This study presents an experimental investigation into the effects of microbial induced carbonate precipitation (MICP) treatment factors on the shear behavior of MICP-treated loess soil. Several groups of loess samples were prepared and subjected to MICP treatment with varying cementation reagent concentration, calcium source, and curing duration across three levels. The results indicate that the shear strength of MICP-treated loess achieves optimal performance when treated with the cementation reagent concentration of 1.0 M, cured for 14 days, and using calcium chloride as the calcium source. Compared to untreated loess, the cohesion and internal friction angle increased by approximately 77% and 26%, respectively. To evaluate the influence of these treatment variables, orthogonal analysis was performed on the obtained shear strength parameters. The analysis indicates that the cementation reagent concentration is the primary factor influencing shear strength, followed by the calcium source and curing duration. Additionally, scanning electron microscopy (SEM) tests were performed to investigate the microstructure of the MICP-treated samples. The results reveal that calcium carbonate significantly enhances the loess structure by creating large effective bonding areas, which in turn increases the bridging force. As a result, the overall shear strength of the treated loess shows a marked improvement compared to the untreated samples.