Research Team Creates Soil-Based Nails, Alternative to Cement-Based Ground Technologies

Achievement date: 
2016
Outcome/accomplishment: 

A team at the NSF funded Engineering Research Center (ERC) for Bio-mediated and Bio-inspired Geotechnics (CBBG), headquartered at Arizona State University, have demonstrated on a laboratory bench-top scale the use of enzyme-induced carbonate precipitation (EICP) to create soil nails for ground reinforcement and excavation support. 

Impact/benefits: 

The experiment demonstrates an application of EICP as an alternative to conventional soil nailing, which involves inserting a steel bar into a drilled hole with a Portland cement grout. Such technology is used in more than 40 percent of construction excavations in Europe, and increasingly in the US. 

Explanation/Background: 

Engineering applications of EICP have been hindered by the rapid rate at which the carbonate precipitation reaction occurs. This rate is typically so rapid it prevents the dispersion of the cementation solution, resulting in a thin stabilized crust at the interface between the soil and the injection point for the precipitation solution.

CBBG researchers found a way to delay precipitation, allowing the cementation solution to penetrate into the soil and create a more uniform stabilized mass. This proprietary technique was successfully employed in creating a small-scale soil nail wall described above, allowing the cementation solution injected through the top of the inserted tubes to flow around the tube and create an unfirmly stabilized mass.

EICP soil nailing offers a sustainable alternative to the existing methods (typically involving steel and cement) where ground conditions are appropriate, such as with gravel, sand, and silt that can be penetrated by the EICP solution. Further development of this technology can make a significant impact in ground reinforcement and excavation support.