Enhancement of MICP-Treated Sandy Soils against Environmental Deterioration

Microbially induced calcite precipitation (MICP) is a sustainable biological ground improvement technology that is capable of improving the engineering properties of soil. A laboratory study was conducted to investigate the influence of some key environmental parameters on the long-term engineering performance of MICP-treated sandy soil, including wet-dry cycles, freeze-thaw cycles, and acid rain conditions, and to study the effect of enhancement through fiber reinforcement and multiple MICP treatments. Experimental results indicated that durability of MICP-treated soil was weak in wet-dry cycles, freeze-thaw cycles, and acid rain conditions. The unconfined compression strength (UCS) of MICP-treated soil had nearly 80% reduction after one wet-dry cycle, 58% reduction after 15 freeze-thaw cycles, and 83% reduction after 15 days immersed in acid rain solution with the pH of 3.5. Fiber reinforcement mainly enhanced the ductility of MICP-treated samples. The failure strain of fiber-reinforced samples reached 1.6% compared with unreinforced samples of 0.4% after 5 wet-dry cycles. Multiple treatments enhanced the durability of MICP-treated samples. The UCS of multiple MICP-treated samples had no significant reduction after wet-dry and freeze-thaw cycles. For quadruple MICP-treated samples, a 51.9% UCS still remained after 15 days immersed in acid rain solution with the pH of 3.5.