Numerical Analysis of Two-Dimensional Tank Experiment of Microbially Induced Desaturation (MID) in Layered Silts and Sands

A numerical reactive transport model was developed to simulate microbially induced desaturation (MID), an emerging bio-mediated ground improvement technique. MID employs nitrate-reducing microorganisms to produce gas bubbles that desaturate granular soils, thereby enhancing the cyclic shear strength of the soil. MID is of particular interest due to its potential to mitigate earthquake-induced soil liquefaction non-disruptively, for example, underneath existing structures. The model couples fluid flow with reactive transport and predicts the distribution of substrates and products and changes in porosity, permeability, and degree of saturation from MID. The numerical model was implemented in COMSOL Multiphysics finite element software and validated using bench-scale tank experiment results. Comparison of changes in the degree of saturation and electrical conductivity, time-lapse images, and the breakthrough curves observed during the experiment with the results of the numerical simulations provides insight into the distribution of biomass and consequent varying reaction rates throughout the tank.