Liquefaction Mitigation of Sands with Nonplastic Fines via Microbial-Induced Partial Saturation

Abstract

A review of liquefaction case histories shows that sand deposits containing some fines were common in past liquefaction events. While current liquefaction mitigation measures are mostly applicable to clean sands or open sites, development of nondisruptive techniques applicable to sands containing fines is critical. This paper examines the application and performance of microbial-induced partial saturation (MIPS) for liquefaction mitigation of sands with various silt contents. The investigation consisted of a set of undrained strain-controlled cyclic direct simple shear (DSS) tests on untreated and MIPS-treated samples. Experimental results suggested that high excess pore pressure was developed in untreated clean and silty sand specimens, which led to liquefaction depending on the shear strain level. Regardless of fines content and induced shear strain amplitude, MIPS-treated samples with only 4%–5% reduction in degree of saturation did not liquefy. A semi-empirical equation was adopted to predict the excess pore pressure generation in partially saturated conditions. The equation is able to reasonably predict the excess pore pressure generated in both clean and silty sands with variable degrees of saturation.