Abstract

The application of MICP has been successfully studied in granular soils due their high permeability. However, in soils with high fines content the injection of MICP has been limited due the difficulty to distribute the additives because of their low permeability. With the aim of the present research, an alternative application of MICP is being studied, here the biological additive included into the compaction water, overcoming the difficulty of application by injection in soils such as silts and clays, and as a soil improvement method could help to avoid soil replacement by loan material. Two applications are being studied. Firstly, a silty-sand residual soil called Maicillo, which is abundant in coastal mountains of Chile. This weathered material presents significant cohesion in its natural condition. However, once excavated and compacted, shear strength and stiffness are significantly reduced. Our laboratory experimental results (isotropic and triaxial compression with bender elements) show that MICP on remolded Maicillo improves its mechanical properties, allowing to recover partially the undisturbed behavior. Secondly, MICP was applied on a remolded expansive clay. Laboratory consolidation/swelling tests and a field testing facility specially built were used to assess the effectiveness of MICP to reduce swelling. The results suggest that the chemical process involved in calcite precipitation reduces swelling. Preliminary microstructural characterizations on treated clays indicates a change in the evaporation water temperature on Temperature Programmed Desorption (TPD) and also a slight change in the pore distribution with the Nitrogen adsorption-desorption test.