Centrifuge Model Testing of Liquefaction Mitigation via Microbially Induced Calcite Precipitation

A set of saturated Ottawa sand models was treated with microbially induced calcite precipitation (MICP) and subjected to repeated shaking events using the 1-m radius centrifuge at the UC Davis Center for Geotechnical Modeling. Centrifuge models were constructed to initial relative densities ($D_{R0}$) of approximately 38% and treated to light, moderate, and heavy levels of cementation (calcium carbonate contents by mass of approximately 0.8%, 1.4%, and 2.2%, respectively) as indicated by shear wave velocities ($\mathrm{light}\approx 200\mathrm{m}/\mathrm{s}$, $\mathrm{moderate}\approx 325\mathrm{m}/\mathrm{s}$, and $\mathrm{heavy}\approx 600\mathrm{m}/\mathrm{s}$). The cemented centrifuge models were compared to a pair of uncemented saturated Ottawa sand models with initial $D_{R0}\approx 38$ and 53% and subjected to similar levels of shaking. Cone penetration resistances and shear wave velocities were monitored throughout shaking to investigate (1) the effect of cementation on cone penetration resistance, shear wave velocity, and cyclic resistance to liquefaction triggering; and (2) the effect of shaking on cementation degradation. Accelerometers, pore pressure transducers, and a linear potentiometer were used to monitor the effect of cementation on liquefaction triggering and consequences. Cone penetration resistances and shear wave velocities were sensitive to light, moderate, and heavy levels of cementation (increases in penetration resistance from 2 to 5 MPa, from 2 to 10 MPa, and from 2 to 18 MPa and increases in shear wave velocity from 140 to $200\mathrm{m}/\mathrm{s}$, from 140 to $325\mathrm{m}/\mathrm{s}$, and from 140 to $660\mathrm{m}/\mathrm{s}$, respectively), and were able to capture the effects of cementation degradation.