Matt Bradford, Writer for Ontario Road Builders Association & Ontario Good Roads Association's publications
In 2004, Dr. J.P. Giroud and Dr. Jie Han advanced the field of geosynthetics when they published their methodology for applying geosynthetics in unpaved structures in the ASCE Journal of Geotechnical and Geoenvironmental Engineering. The methodology has since been adopted by the Federal Highway Administration in 2008, and is considered at the forefront among industry professionals.
Karan Jalota, an applications specialist with Nilex Inc., is one of those professionals. For a better understanding of the doctors' original research, and the current geosynthetic practices, we reached out for his perspective.
What did Dr. J.P. Giroud and Dr. Jie Han's research bring to the field of geosynthetics?
When Dr. Giroud and his previous colleague Dr. Noiray started research with geotextiles, they devised equations which indicated that if you used a specific type of geosynthetic fabric, you could potentially provide an enhancement to the subgrade bearing capacity. Therefore, one could look at reducing the thickness of an unpaved structure.
Dr. Han came in on the next phase of this research, which was extremely important. They published the Giroud-Han Method for applying geosynthetics on unpaved roads in 2004, which helped engineers better understand the extent of their work and what would need to be done to calibrate products to the G-H equation.
For example, if I have geogrid “X” from one company, and someone else has geogrid “Y” from another, they may say it's the same, but my question to them would be: Have you done the testing and validated it with multiple subgrade and loading conditions? Have you calibrated and provided a calibration factor to put into an equation like the G-H equation? That is why Dr. Giroud and Dr. Han's research is so important, and why it's been at the forefront of the industry for 30 years.
How has that methodology been interpreted since?
The original research is typically misunderstood because one of the key boundary conditions was based on 10,000 axel passes. Today, unpaved structures certainly carry more, so when somebody says they're going to go up to 100,000 axel passes – or even 10 million – they forget the original methodology was based on 10,000. To go higher, you need to conduct testing. It is also recommended to have a third-party review of the data and results, and for the reviewer to provide conclusions.
Also, the original methodology was capped at a specific axel load. Similar to the AASHO Road Test (circa 1960), their testing was with vehicles with much lesser weights than the vehicles we have currently. That’s one example of factors people occasionally do not take into consideration. You really need to be extremely cognizant of what the original methodology was based upon.