The enzyme-induced carbonate precipitation (EICP) method has been investigated to improve the hydromechanical properties of natural soil deposits. This study was conducted to explore the stiffness evolution during various stress scenarios. First, the optimal concentration of urea, CaCl2, and urease for the maximum efficiency of calcite precipitation was identified. The results show that the optimal recipe is 0.5 g/L and 0.9 g/L of urease for 0.5 M CaCl2 and 1 M CaCl2 solutions with a urea-CaCl2 molar ratio of 1.5. The shear stiffness of EICP-treated sands remains constant up to debonding stresses, and further loading induces the reduction of S-wave velocity. It was also found that the debonding stress at which stiffness loss occurs depends on the void ratio, not on cementation solution. Repeated loading-unloading deteriorates the bonding quality, thereby reducing the debonding stress. Scanning electron microscopy and X-ray images reveal that higher concentrations of CaCl2 solution facilitate heterogeneous nucleation to form larger CaCO3 nodules and 11-12% of CaCO3 forms at the inter-particle contact as the main contributor to the evolution of shear stiffness.
Bibliographical noteFunding Information:
This work was supported by the Land and Housing Institute (LHI) grant funded by the Korea Land and Housing Corporation, the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (2016R1A2B4011292), and the research fund of the Korea Agency for Infrastructure Technology Advancement (KAIA) (18CTAP-C142849-01).
All Science Journal Classification (ASJC) codes
- Civil and Structural Engineering
- Geotechnical Engineering and Engineering Geology