Experimental and Numerical Analysis of a Field Trial Application of Microbially Induced Calcite Precipitation for Ground Stabilization

A field trial evaluated the potential of microbially induced calcite precipitation (MICP) through urea hydrolysis for ground stabilization. A bioaugmentation approach was employed in which locally enriched bacteria were injected, followed by an amendment solution containing urea and calcium chloride. Results from cone penetration tests and soil analysis were inconclusive about the obtained ground stabilization. In situ monitoring results were analyzed using a two-dimensional (2D) numerical reactive transport model to evaluate the process performance, in which the effective thickness of the treated layers, the average reaction rate, and a dilution factor accounting for the water extracted from the less-permeable layers were varied, and the results of the different numerical simulations were compared with the field measurements. The combined results of monitoring and numerical modeling demonstrated that treatment was limited to approximately 5% of the total soil volume. The conversion efficiency was significantly lower than expected, and the substrates spread farther than originally intended, which could be attributed to the heterogeneous soil profile with a large amount of fines, causing preferential flow through the more-permeable layers and possibly hydraulically induced fractures.