Strength improvement in silty clay by microbial‑induced calcite precipitation

摘要

The application of MICP (microbial-induced calcite precipitation) to clays has been restricted due to their low permeability and small pore size, which limit bacterial mobility. The authors proposed an injection method for introducing solutions into a silty clay for MICP in the pore space. Test results showed that injecting equal volumes of bacterial solution and cementation solution resulted in 200% soil strength. The soil strength was estimated using a miniature cone penetration test, which provided a continuous cone resistance profile. The strength profile of the improved samples clearly showed that the peak strength occurred at the top portion of the samples, which implied that bacteria and urease traveled through the soil and MICP occurred. After the injection, 70-90% of the soil volume was improved through MICP. An analysis of drainage solutions after a few days showed calcite precipitation, which indicated that the urease reaction was still active in the drainage. These results can conclude that MICP is applicable to silty clays with similar properties, such as low permeability, low pH, and small pore size.