Effect of microbially induced cementation on the instability and critical state behaviours of Fraser River sand

Microbially induced calcite precipitation (MICP) is a naturally driven biological process that harnesses the natural metabolic action of bacteria to induce the precipitation of calcium carbonate and alter soil engineering properties. This paper presents the results of using MICP to improve the monotonic undrained yield and critical strengths of Fraser River sand specimens. Bacteria called “Sporosarcina ureae” are employed as a ureolytic organism to achieve MICP. The formation of calcite cementation among sand particles is confirmed using scanning electron microscopic images and X-ray compositional analysis of cemented sand clusters. The progress of MICP cementation is assessed by measuring the velocity of a shear wave (VS) traveling through the specimen. The results show that VS starts to increase just as the calcium solution is introduced into each specimen after soaking the samples with the bacterial solution. Improvement in monotonic strength of sand samples is subsequently measured in a series of direct simple shear tests. Due to the combined effects of particle cementation and densification, the sand’s undrained and drained monotonic shearing strengths are significantly enhanced.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author