UC Davis

Microbially induced calcite precipitation (MICP) is an environmentally conscious ground-improvement method that can enhance the engineering properties of granular soils through the precipitation of calcium carbonate (CaCO3) on soil particle surfaces and contacts. Although numerous studies have shown the ability of biocementation to improve the liquefaction resistance of loose sands, the effects of light cementation levels on undrained cyclic behaviors have remained relatively unexplored. A series of undrained monotonic and cyclic direct simple shear tests were performed to examine the effect of light biocementation (ΔVs<100 m/s and CaCO3 contents <0.9%) on the liquefaction triggering and post-triggering behavior of loose Ottawa F-65 sand subjected to varying loading magnitudes [cyclic stress ratio (CSR)=0.1 to 0.3]. Results suggest that the presence of light biocementation can significantly improve the liquefaction triggering resistance of loose sands, with log-linear increases in the number of cycles required to trigger liquefaction, which consistently correlated with cementation-induced Vs increases. Despite these remarkable pretriggering improvements, almost no improvements were observed in post-triggering strain accumulation and postcyclic reconsolidation behaviors, with Vs measurements indicating that small-strain improvements were largely erased following shearing events.