The Effect of Microbial Induced Carbonate Precipitation on Fine-Grained Mine Tailings

Microbial induced carbonate precipitation (MICP) is a bio-mediated cementation process that uses biological activity to improve the geotechnical properties of granular soils. MICP, or more generally bio-cementation, has the potential to improve the resilience of granular materials to prevent phenomena such as liquefaction and erosion. Bio-cementation processes have also been previously used to stabilize byproduct materials such as coal ash and mature fine tailings. Fine-grained mine tailing sediments, or "slimes," are typically weakened layers that negatively affect the overall performance of tailings impoundments and dams, and have previously contributed to catastrophic failures of these structures. In this study, two sets of fine-grained tailings from gold and iron mines are tested to determine their compatibility with MICP. The remolded undrained shear strength was assessed for these byproduct materials over a range of different water contents to compare with bio-cemented samples. The bio-cemented samples indicated significant increases in remolded undrained shear strength, ranging from two to five times the natural samples' strength. Analytical microscale testing methods were utilized to determine the soil fabric and structure (i.e., X-Ray Diffraction and Cryo-Scanning Electron Microscopy). In particular, the mineralogy of the soils was examined to better understand the physical and chemical interactions of the soil grains, both before and after cementation. The results of this study indicate that MICP strengthens the fabric of the fine-grained tailings, which may result in improved performance of fine-grained mine tailings.