Experimental Tests of Soil Reinforcement Against Erosion and Liquefaction by Microbially Induced Carbonate Precipitation

An innovative soil reinforcement method developed since 2004 is currently being adapted for hydraulic structures in the frame of the BOREAL project. The objective is to prevent mechanical failure of the soil due to internal erosion or liquefaction. The method is based on microbially induced urea-based carbonate precipitation. Four different erosion test apparatus have been used to assess the methodology: Contact Erosion Tests, Hole Erosion Test, Jet Erosion Test and suffusion tests. All the tests results indicate a strong increase of resistance already with a small percentage of formed calcite (~2–4%). In parallel, tests were performed in a CNR laboratory at a larger scale (8 × 4 × 2.25 m). The first experiment was performed on a homogeneous Fontainebleau Sand. The second and third tests were performed on sandy gravels, which are highly representative of the soil layers that could be treated with this method. These tests validated the effectiveness of the treatment on soils with open porosity, under natural Darcy velocity up to 10⁻³ m/s. Finally, the fourth test dealt with the treatment of an interface between a coarse and a fine soil layer, underlying the interest of the method for remediation in the case of contact erosion problems.