Laboratory Tests On Mitigation Of Soil Liquefaction Using Microbial Induced Desaturation And Precipitation

Microbial induced desaturation and precipitation (MIDP) is an emerging bio-mediated ground improvement method in which nitrate-reducing bacteria in the soil are stimulated to produce biogas and biominerals. In this study, the potential of MIDP for mitigating soil liquefaction was evaluated using a modified triaxial setup. Modifications to the triaxial test setup allowed the change in the degree of saturation during treatment and the mechanical response to cyclic and monotonic loading to be measured. An experimental procedure was developed to simulate the in situ treatment process of a sand layer underneath an embankment along the Fraser River in Richmond, British Columbia, Canada, which was susceptible to liquefaction. Denitrifying microbes were enriched from locally collected soil. Reconstituted samples were treated with a single MIDP treatment cycle under similar stress conditions as encountered in the field. Triaxial consolidated undrained cyclic and monotonic tests were performed to investigate the mechanical response of the treated soil. Results showed that a single MIDP treatment cycle reduced the degree of saturation to 80 % and produced an average calcium carbonate content of 0.086 %, and significantly increased the cyclic shear resistance.