Bio-Inspired Soil Improvement Using EICP Soil Columns and Soil Nails

Enzyme induced carbonate precipitation (EICP) for vertical columnar stabilization and soil nailing has been demonstrated in bench scale testing. In EICP, precipitation of calcium carbonate (CaCO₃) is induced via hydrolysis of urea using free urease enzyme. The enzyme is introduced into the soil in an aqueous solution containing urea and calcium ions to precipitate CaCO₃. The precipitated CaCO₃ improves the strength and stiffness and increases dilatancy of the soil by filling soil pores, roughening the soil particles, and binding the particles together. EICP was used to improve soil around 51 mm- and 76 mm-diameter vertical perforated plastic pipes in 19 L buckets and a 1 m³ soil box, respectively. EICP solution was also injected through a 9.5-mm diameter perforated tube to create inclined columns to model soil nails. These tests demonstrate the feasibility of using EICP to create cemented soil columns for foundation support and soil nailing.