Numerical modelling of biogenic desaturation and precipitation

Microbial Induced desaturation and precipitation is being investigated for its potential as ground improvement method. In this process a solution containing dissolved calcium, organic carbon and nitrate is injected in the soil. Indigenous nitrate reducing bacteria are stimulated and produce a mixture of biomass, calcium carbonate minerals and a mixture of nitrogen and carbon dioxide gas. Formation of gas in the sand desaturates the soil and the entrapped gas bubbles can dampen pore pressure build up during cyclic loading, mitigating soil liquefaction and collapse of buildings during earthquakes. Formation of biomass and biominerals fill up the pores and reduce the hydraulic conductivity, while formation of calcium carbonate minerals at the interparticle contacts can increase strength, stiffness and permeability. In this study a numerical model is developed to predict the distribution of substrates and metabolic products at field scale and evaluate the performance of a recently performed field trial. The model uses monitoring data from the field trial as input parameters to define the geometry and fit kinetic and geometrical parameters that describe the reactive transport.