Information for lesson "Lifetime Predictions of Exposed and Nonexposed Geosynthetics - Dr. Robert Koerner - 1.5 PDH"
Description: A most frequently asked question regarding all types of geosynthetics is, “How long will they last?” This webinar addresses the question from both exposed and nonexposed perspectives. It utilizes for incubation purposes laboratory ultraviolet fluorescent tube weathering devices to simulate exposed conditions. Fifteen geosynthetics are evaluated; six geomembranes, two geogrids, four turf reinforcement materials and three geotextiles. Each have been incubated at 80°C, 70°C and 60°C until halflife of strength retained and elongation retained have occurred. The data is then extrapolated down to 20°C for laboratory halflife values. The calculations then progress to using site-specific radiation to obtain the equivalent field life. Arizona conditions are illustrated although the procedure is applicable worldwide.
The nonexposed conditions are evaluated based solely on a high density polyethylene (HDPE) geomembrane and uses landfill incubation cells at four elevated temperatures. Using full depletion of antioxidants, induction time, and halflife at 20°C, the total lifetime is obtained. The approximate lifetime for this geomembrane is 440 years! Since the incubation times took 12 years, other nonexposed geosynthetics were not evaluated with the conclusion that the buried (nonexposed) situation is a moot point for most geosynthetics and their respective applications.
Objectives: Webinar participants will gain familiarity of how lifetime prediction of all polymeric materials are made, including geosynthetics. The technique is incubation at several high temperatures so as to accelerate degradation, measure property changes, and then to extrapolate down to site-specific (i.e., actual) temperatures so as to estimate lifetime. The technique is called time-temperature-superposition followed by Arrhenius modeling.
The webinar is a result of over 12-years of GSI/GRI research focused on providing lifetime estimates of geosynthetics. For the exposed situation laboratory fluorescent ultraviolet weathering devices are used. For the nonexposed (buried) situation complete laboratory simulation is used. The former evaluates 15-different geosynthetics, the latter only HDPE geomembranes. It is seen that the exposed situation lifetimes are within the usual civil engineering lifetimes expectations. For the nonexposed situation lifetimes are well beyond civil engineering application lifetimes, in this case 440 years.
· Learn about lifetime prediction methods for polymers · Learn specifically about the methodology with respect to geosynthetics · Examine the lifetimes of 15 different geosynthetics under simulated exposed conditions · Understand the large increase in lifetime when geosynthetics are nonexposed, i.e., buried · Understand that lifetime of nonexposed geosynthetics are generally far greater than typical civil engineering applications and other components
Public and private regulators and facility owners, civil and industrial engineers, property developers, contractors and installers, academic and research groups, the general lay public and others desiring technically related information on this most frequently asked question.
Dr. Robert M. Koerner’s (Professor Emeritus of Civil Engineering at Drexel University and Director Emeritus of the Geosynthetic Institute) interest in geosynthetics spans over thirty-five years of teaching, research, writing and advising. He holds his Ph.D. in Geotechnical Engineering from Duke University. He is a registered Professional Engineer in Pennsylvania, a Distinguished Member of ASCE, a Diplomate of the GeoInstitute and a member of the National Academy of Engineering. Bob has authored and co-authored about 650 papers on geosynthetics and geotechnical topics in journals and at national and international conferences. His most widely used publication is the sixth edition of the textbook entitled “Designing with Geosynthetics”. He is the founding director of the Geosynthetic Institute which is a nonprofit research and development organization dedicated to the proper use of geosynthetics in its myriad applications. The institute also provides laboratory accreditation and inspection certification programs.