Institute for Transportation

About the research

While levee embankments are the first line of defense for urban flooding, recent flooding events have revealed widespread slope instability of embankments around the country that can lead to levee failures. This work aimed to improve the slope stability of earthen levees by strengthening the soil through the use of a biologically-inspired technique called biocementation.
The major objective of this study was to determine the optimal and most practical biocementation method that results in the best performance of levee slopes under various flooding conditions.
A novel biocementation method called bacterial enzyme-induced calcite precipitation (BEICP) was tested. This method differs from the well-studied microbial-induced calcite precipitation (MICP) method mainly in the size of the biological agent (whole bacterial cell vs. enzyme), which influences the agent’s mobility in soils of different grain sizes.
The BEICP methods for soil strengthening were optimized in laboratory-scale column experiments. The optimized methods were then used to construct levees in an experimental flume system.
The results indicated that the BEICP treatment resulted in significant strengthening of the surface of the soil specimens, which were measured as increases in unconfined compressive strength. The strengthened samples were able to resist erosion for a longer time period under overtopping scenarios of water challenges with high water velocity in a flume. Therefore, BEICP offers a sustainable and economical method for treatment of soil surfaces to improve erosion resistance.
The results of this study will help mitigate flooding events that could cause major issues in transportation infrastructure and traffic safety.

Funding Sources:
Iowa State University ($82,233.00)
Midwest Transportation Center
USDOT/OST-R ($80,000.00)
Total: $162,233.00

Contract Number: DTRT13-G-UTC37