Microbially Induced Carbonate Precipitation for Seepage-Induced Internal Erosion Control in Sand-Clay Mixtures

Earth embankment dams are one of the most commonly constructed hydraulic infrastructures worldwide. One mode of dam failure is piping through the embankment, which is initiated by internal erosion of soil particles inside dams. In this study, the applicability of microbially induced carbonate precipitation (MICP) for internal erosion control is examined in the laboratory using sand-kaolin mixtures of different particle sizes. A series of internal erosion tests are conducted using a newly designed rigid-wall column erosion test apparatus, which allows independent control of MICP treatment. Erosion rate/coefficient, volumetric change, and permeability are characterized during the internal erosion process. It is found that MICP treatment facilitates the reduction of erosion and volumetric contraction of sand-clay mixtures investigated in the current study. Carbonate precipitation increases the erosion resistance of sand-clay mixtures by absorbing/coating fine particles directly and bridging the contacts of coarse particles. An improved effectiveness of internal erosion control is observed in the sand-clay mixture having a higher gap ratio. This observation is due to the inherently large porosity, which hosts more carbonate precipitation. The difficulty of bacteria and chemical injection in sand-clay mixtures triggers the flushing of produced calcium carbonate, which reduces the overall carbonate content and MICP treatment efficiency. The spatial distribution of precipitation within the soil is also altered. (C) 2016 American Society of Civil Engineers.