Cementation of Sand Soil by Microbially Induced Calcite Precipitation at Various Degrees of Saturation

4 A newly emerging microbiological soil stabilization method, known as microbially 5 induced calcite precipitation (MICP), is tested for geotechnical engineering 6 applications. MICP is a promising technique that utilizes the metabolic pathways of 7 bacteria to form calcite precipitation throughout the soil matrix, leading to an increase 8 in soil strength and stiffness. This paper investigates the geotechnical properties of a 9 sand bio-cemented under different degrees of saturation. A series of laboratory 10 experiments was conducted, including sieve analysis, permeability, unconfined 11 compressive strength, consolidated undrained triaxial, and durability tests. The results 12 indicate that higher soil strength can be obtained at similar CaCO3 content when the 13 treatment is performed under low degree of saturation. Fine sand samples exhibited 14 higher cohesion but lower friction angle than coarse sand samples with similar CaCO3 15 content. The results also confirm the potential of MICP as a viable alternative technique 16 for soil improvement in many geotechnical engineering applications, including 17 liquefiable sand deposits, slope stabilization and subgrade reinforcement. The freeze 18 thaw and acid rain resistance of MICP treated sand has also been tested. 19 CE Database keywords: Soil stabilization; Cementation; Microorganisms; Calcium 20 carbonate; Durability. 21