Centrifuge Model Testing of Liquefaction Mitigation via Microbially Induced Calcite Precipitation

A set of centrifuge model tests were conducted to evaluate the mitigation of earthquake-induced liquefaction of loose Ottawa sand treated with microbially induced calcite precipitation (MICP). The bio-mediated MICP process can facilitate the formation of cemented bonds at particle-particle contacts, which can induce large changes in soil engineering properties including small-strain stiffness, volumetric behavior, and strength. In this study, two models were constructed in a flexible shear beam container and tested using the 1-m radius centrifuge at the University of California, Davis. The liquefaction triggering behavior of a lightly cemented (calcite content approximate to 1.2% by mass) MICP treated model is compared to an untreated model of the same initial relative density. Models were subjected to multiple sinusoidal shaking events during which accelerations, pore pressures, and surface settlements were monitored. Shear wave velocity was measured prior to each shaking event and miniature cone penetration soundings were performed at select times during testing.