Numerical Investigation of Biogrout: a New Soil Improvement Method Based on MICP

Abstract

Ground improvement is essential in regions where the desired mechanical properties of soil are not suitable for the particular use. Microbial induced calcite precipitation (MICP) offers an alternative solution to a wide range of civil engineering problems. The microbial urease catalyzes the hydrolysis of urea into ammonium and carbonate. The produced carbonate ions precipitate in the presence of calcium ions as calcium carbonate crystals. Recently, MICP has also been shown to improve the undrained shear strength, confined compressive strength, stiffness and liquefaction resistance of soils and offers potential benefits over current ground improvement techniques. Biogrout is the new ground improvement method where MICP is used to achieve soil strength and stiffness. There is a need to clearly understand the various bio-geo-chemical processes that take place during biogrout in order to predict the enhancement in different mechanical properties of soil. The aim of this master's thesis is to present a numerical model for biogrout process for one-dimensional column experiment, investigating the influence of different injection schemes on the distribution of precipitated calcite within the porous media. In this work, a multi-component bio-geo-chemical model was used, based on the coupled code OpenGeoSys-PhreeqC. The applied model describes the physical and chemical process during the different injections. The results show that the reduction of porosity and permeability can be manipulated using different injection schemes.