Mitigation of Liquefaction Triggering and Foundation Settlement by MICP Treatment

Centrifuge modeling was used to study the performance of loose sand treated with microbial-induced calcium carbonate precipitation (MICP) to improve liquefaction resistance to triggering and reduce the total and differential settlement of shallow foundations. The MICP-treated sand was surrounded by untreated loose and dense sand zones with initial relative densities of $D_R=40\%$ and 75%, respectively. A simple foundation system applied a contact stress of 270 kPa. The model was subjected to five uniform sinusoidal shaking events with a progressive increase in amplitude per event. Cone penetration resistance, shear-wave velocity, accelerations, excess pore pressures, and settlements were measured. The MICP treatment improved liquefaction resistance of the soil, and the presence of loose and dense sand layers near the MICP-treated sand affected the dynamic response and settlement of the soil and foundation systems. The total settlement and maximum angular distortion of the foundation systems were reduced by up to 57% and 75%, respectively, depending on soil layering and MICP improvement depth. Collectively, the results show that MICP improvement can be effective in reducing building damages induced by earthquake shaking.