Executive Summary : | One of the most damaging hazards of earthquakes is liquefaction, which causes the ground to flow like a liquid under specific dynamic loading conditions. Liquefaction is prevalent in loose cohesionless sands in which the interparticle contacts are mainly governed by friction. Among the several available techniques for mitigating liquefaction in loose sands, densification, grouting and earthquake drains are most widely used. Chemical stabilisation at shallow depths and grouting to deeper depths can mitigate liquefaction to a great extent. However, these chemicals migrate into the groundwater and cause health hazards, which is a threat to environmental sustainability. The latest addition to the list of effective liquefaction mitigation techniques is the bio-cementation of sands. Enzymatic microbial action would be a novel and safe method since the additives are naturally derived and do not cause any environmental risks. Many of the recent studies in this direction showed great promise in small-scale laboratory experiments. However, the large-scale application of this method and the fundamental science behind particle cementation through microbial interactions are still elusive. The proposed project aims at small-scale element tests, shaking table model tests and digital image-based microanalysis to understand, analyse and quantify the effects of bio-cementation for liquefaction mitigation of sands. This project will have three stages, the first stage focuses on element tests on enzyme stabilised sand specimens, the second stage is dedicated to shaking table model tests on enzyme stabilised sand beds, and the final stage consists of the analysis of experimental results and correlating them to the fundamental micro-level changes in sands investigated through digital image analysis. |