Monitoring and Characterizing the Whole Process of Microbially Induced Calcium Carbonate Precipitation Using Electrical Resistivity Tomography

Microbially induced calcium carbonate precipitation (MICP) is a promising biomediated soil improvement technique. Compared with traditional ground improvement methods, MICP has proven extensive applicability and ecological benefits. However, heterogeneity during MICP treatment is a major obstacle in engineering applications, causing a strong need for monitoring methods to investigate the process of treatment and optimize the subsequent design scheme. Electrical resistivity tomography (ERT) is a noninvasive spatially resolved monitoring technique for visualizing the distribution of both treatment solution and precipitated calcium carbonate in MICP treatment. In this study, three-dimensional electrical resistivity tomography was employed to monitor the biocementation process of a sand-packed column. The electrical response over different treatment stages and the final CaCO3 content were collected. Three-dimensional resistivity distribution intuitively characterizes the distribution of treatment solution in the sand column. Changes in the resistivity indicate the spatial variability of the urea hydrolysis and CaCO3 precipitation during the MICP treatment. The final resistivity distribution corresponds to the distribution of precipitated CaCO3, and the relationship between electrical resistivity and CaCO3 content is established. The study serves to explore the potential of ERT as a monitoring method for the MICP treatment process. Of particular interest are its possibilities to contribute to the monitoring of spatial heterogeneity of cementation because of the limitations of traditional techniques in this respect.