Dr. Russell Jones, President of the International Geosynthetics Society, sat down with the Geosynthetic Institute‘s Dr. Robert Koerner to discuss GSI’s 12-year study on the long-term performance and aging of geotextiles and geomembranes, with a focus on the applicability of the research for lifetime predictions.
The interview took place in April in Miami during GeoAmericas 2016, the 3rd Pan-American Conference on Geosynthetics.
Koerner delivered one of the four keynote addresses at GeoAmericas 2016. His topic, “Lifetime Predictions of Exposed Geotextiles and Geomembranes,” resonated well with the conference audience. It also addressed one of the most important and most frequently asked questions: How long will these materials last?
The lecture was co-authored with Drs. Grace Hsuan and George Koerner, also of GSI, and is included in the three-volume set of GeoAmericas 2016 papers.
As the field of geosynthetics advances into 40+ year records of in-service projects, the continuing revelations from research such as GSI has conducted add significant support. The long-term performance predictions of the past are proving accurate, and newer research both underscores that longevity as well as establishes stronger confidence and more detailed factors for evaluation and monitoring.
In the interview, Koerner notes that the study is in part important simply for the confidence it can provide regulators and facility owners, who “do everything except geosynthetics.”
Essentially: While it can be easy for professionals in geosynthetics to have the project experience and research knowledge on which to feel confident, imparting the information to the people who ultimately must sign off on a project design—someone like a regulator—remains an enormous challenge, even in this established field. The research provides an accessible view of material aging and performance.
LIFETIME PREDICTIONS FOR GEOSYNTHETICS
The long-term study provides some fascinating numbers, both from the on-going research and from previous studies. The interview summarizes some of these results and adds insightful comments on the thoroughness that underlies geosynthetic research, development, manufacturing, and field monitoring and understanding.
Early in the interview, for example, Russell Jones highlights how covered geomembrane studies have indicated that for 1.5mm thick geomembrane at 20°C a lifetime of around 500 years can be extrapolated.
“That’s quite an encouraging number,” Jones says.
“Yes, and from my perspective in this area, it would be almost considered an outstanding number,” says Robert Koerner. “With time, I understand more about the chemistry of the situation, about how these degradation mechanisms have to diffuse into the material, have to first consume the anti-oxidant, which in this particular case was almost 200 years, and then start to work on the molecular structure. Gradually, the properties decrease, and when they decrease to 50% of the value, that’s the target and we go with data….”
One of the strengths of GSI’s research, and a fact emphasized in the interview, is that the geotextiles and geomembranes that were studied were commercially available and met generic specifications. So, while a manufacturer can adjust the formulation of a geomembrane to significantly enhance lifetime performance for a specific project (or study), the materials that GSI studied represented what is widely available and applicable to many installations. This makes the data of value not only to the general marketplace but to laboratories that want to replicate the research approach going forward.
For information on activities of and membership in the International Geosynthetics Society, visit www.geosyntheticssociety.org.