Effect of Treatment Strategies for MICP-Based Soil Improvement Using Urease-Producing Bacteria

Microbial-induced calcite precipitation (MICP) is one of the bioengineering approaches explored in the last decades for engineering applications such as slope stabilization, liquefaction, and soil erosion. The bio-cementation and bio-clogging properties in MICP-treated soil depend on the treatment sequence (TS) strategies and composition of MICP solutions, which can affect the uniformity of calcium carbonate precipitation and soil properties. The current study compared the seven treatment sequences (TS) for the MICP process with the surface percolation method for soil strength improvement. Results revealed that soil samples followed TS 1 through TS 7 demonstrated bio-cementation properties and showed suitable pH after the treatment. However, the degree of bio- cementation is significantly affected by the treatment sequence. The samples followed by TS 4 and TS 6 have shown adequate bio-cementation and higher unconfined compressive strength compared to other treatment sequences. The microscopic investigations on the specimens extracted from soil samples of TS 1 through TS 7 revealed that TS 4 and TS 6 have more uniform and effective CaCO3 precipitation.