Liquefaction Resistance of Biocemented Loess Soil

Microbially induced calcite precipitation (MICP) is currently appraised to improve sandy soils, but only a few studies use it to solidify loess soil. MICP solidification tests and undrained cyclic triaxial tests were conducted to study the liquefaction resistance of MICP-solidified loess soil samples. The results showed that because calcium carbonate (${\mathrm{CaCO}}_3$) cemented loess soil particles and filled voids in samples, the permeability coefficients of treated samples all decreased. However, the change pattern of the permeability coefficient of samples treated with various conditions was different. For the solidified samples, the liquefaction resistance was improved significantly, and increased treatment cycles resulted in the improvement of the liquefaction resistance. Adding bacterial suspension and the cementation solution together made the sample with initial density of $1.4\mathrm{g}/{\mathrm{cm}}^3$ have higher liquefaction resistance. However, for samples of 1.5 and $1.6\mathrm{g}/{\mathrm{cm}}^3$, adding bacterial suspension and the cementation solution separately also achieved better liquefaction mitigation effects. Increasing total solution volume per treatment cycle improved the liquefaction resistance of the solidified samples. With the increase of ${\mathrm{CaCO}}_3$ content, the number of cycles before liquefaction ($N_L$) and residual strength (${\tau }_r$) exponentially increased, while the damping ratio ($D$) exponentially decreased. Moreover, the linear corrections between specific gravity and ${\mathrm{CaCO}}_3$ content, $N_L$, ${\tau }_r$, and $D$ can be established for MICP-solidified loess soil. In addition, significant corrections also existed between plasticity index and ${\mathrm{CaCO}}_3$ content, $N_L$, ${\tau }_r$, and $D$. Results in this work had a great significance and provided the foundation for the application of the MICP technique for liquefaction mitigation of loess soil.