Precipitation of Calcite by Indigenous Microorganisms to Strengthen Liquefiable Soils

Abstract

Enrichments for indigenous microorganisms capable of hydrolyzing urea in the presence of CaCl₂ were performed on potentially liquefiable saturated soils in both the laboratory and in situ. Following enrichment, treatment of soils with nutrients, CaCl₂ and urea resulted in significant in situ precipitation of calcite, even at depth, by indigenous microorganisms. The biomineralized soils showed properties that indicate calcite precipitation increased their resistance to seismic-induced liquefaction.

Keywords:

• bio-soil
• calcite
• biomineralization
• liquefaction
• bio-stimulation

Acknowledgments

We would like to thank Dr. Thomas Williams, University of Idaho, College of Science-Materials Characterization Laboratory for his XRD analysis of our samples. We would like to thank Joseph Marshal and Greg Watson of the U.S. Corps of Engineers for granting us a special events permit to carry out the field experiment. We would also like to thank Dr. Peter Robertson and Ron Boggess of Gregg Drilling and Testing Inc. for providing us with the miniature cone penetrometer. This work was funded by a grant from the National Science Foundation (070091).