MIDP: Liquefaction Mitigation via Microbial Denitrification as a Two-Stage Process. II: MICP

This paper focuses on the potential for microbially induced carbonate precipitation (MICP) via dissimilatory reduction of nitrogen, or denitrification, to mitigate the potential for earthquake-induced soil liquefaction. Denitrification has the potential to provide mitigation of earthquake-induced soil liquefaction as a two-stage process referred to by the authors as microbially induced desaturation and precipitation (MIDP). In MIDP, desaturation provides mitigation in Stage 1 and MICP provides mitigation in Stage 2. Denitrifying bacteria, when stimulated, have the ability to rapidly desaturate a saturated soil via gas production, thereby significantly increasing the cyclic resistance of the soil. However, because this desaturated condition may not last indefinitely, desaturation is only relied upon to provide temporary mitigation in MIDP. In Stage 2 of MIDP, interparticle cementation, void filling, and particle roughening as a result of MICP significantly improve the strength, stiffness, dilatant behavior, and cyclic strength of the soil, thereby providing long-term liquefaction mitigation (i.e., after denitrification has ceased). This paper describes the use of MICP via denitrification for the long-term mitigation of earthquake-induced liquefaction. Desaturation via denitrification for the short-term mitigation of liquefaction potential is presented in a companion paper. (C) 2017 American Society of Civil Engineers.