Abstract: Microbial induced calcium carbonate precipitation is a new kind of environmental-friendly soil reinforcement technology. Through laboratory MICP grouting test of expansive soil modification using Sporosarcina pasteurii, we investigated into the influences of cementing fluid concentration on the mechanical properties, microstructure and hydraulic characteristics of expansive soil. Moreover, we also revealed the mechanism and effect of modifying expansive soil by MICP technology. Test results demonstrate that MICP is effective in modifying expansive soil. After grouting, the unconfined compressive strength of soil samples increased by 379.4% at most, and the stiffness of soil was also improved. The expansibility and permeability of the samples reduced by up to 25.3 kPa and by three orders of magnitude, respectively. The modification effect ameliorated with the increase of cement concentration; but when the cement concentration reached a certain extent, the modification effect was no longer significant. The research findings verified the effectiveness and feasibility of MICP technology in modifying expansive soil.

Key words: expansive soil, MICP technology, cementing fluid concentration, grouting, mechanical property, microscopic characteristic, hydraulic characteristic