Geosynthetics Solutions for Civil Engineers

April 2004 » Feature Articles
Civil engineering products and materials go through a lengthy process on the path to widespread use and acceptance. The time it takes to move through the process depends upon many factors.
Shanon Fauerbach, P.E.

For example, the discipline of geosynthetics—geotextiles, geomembranes, geonets, geogrids, geosynthetic clay liners, and geocomposites—is said to be in its third stage of development. J.P. Giroud, E.C.P., Ph.D., a leading geosynthetics expert who coined the terms geotextile and geomembrane, said as much in his address to attendees at the International Geosynthetics Society's Fourth International Conference on Geotextiles, Geomembranes and Related Products in 1990: "During the first period, engineers tried to use the products made available by the manufacturers; during the second period, manufacturers tried to make products needed by the engineers." The first two periods took 15 years, and he forecast that the next period would last another 15 years and would entail "extensive cooperation between geotechnical engineers and polymer specialists." This era will devote energy to understanding the durability of geosynthetics, among other priorities.

One world-renowned geosynthetics consultant and instructor contributing to this effort is Ian D. Peggs, Ph.D., P.E., P.Eng., DABFET., a materials scientist by education. He is the founder and president of I-CORP International, Inc., a geosynthetic materials engineering, science, and durability services company that offers field construction and performance expertise. Before forming ICORP, Peggs was a vice president and principal with GeoServices, Inc., and president and co-founder of the geosynthetics testing laboratory, GeoSyntec, Inc., USA. (These two companies make up GeoSyntec Consultants.)

For the past 20 years, Peggs has investigated and tested polymers, primarily geosynthetics, and has learned much about the materials' durability. His special interests include failure analysis and nondestructive testing.

His vast research, experiences, and knowledge have heightened the geosynthetic community's understanding of these products. His contributions to the industry include editing or contributing to five books, writing more than 120 publications, and contributing to various committees in the geosynthetics industry, as well as to organizations committed to education and development of testing standards. Additionally, he developed the website www.geosynthetica.net, an industry- supported technical information and news resource, to educate engineers on the proper use of geosynthetics.

His influence has been recognized with the nomination and receipt of various industry awards. In fact, he received the International Geosynthetics Society Special Recognition Award in 1994 for his work on the influence of polymer microstructure on the performance of geomembranes.

It was with great pleasure that I had the opportunity to ask Peggs about the state of the industry. As a member of the collaborative team that is expected to carry geosynthetics into the next era, he offers resources and tips for engineers interested in pursuing a deeper understanding of geosynthetics.

State of the Industry

Q: Do you believe that the civil engineering community as a whole is applying geosynthetics as readily as it should be, given the extent and cost of land development and rehabilitation occurring nationwide?

Peggs: I do not. [Civil engineers] are simply not aware of the availability and performance characteristics of geosynthetics. Resources are insufficient to educate the number of people that need to know about geosynthetics. And when they understand them, they have difficulty believing that such thin, light, flexible materials are capable of performing adequately.

Q: For what application(s) or purpose( s) within the civil engineering industry are geosynthetics being underutilized? Should this situation be of concern to the industry?

Peggs: Waterproofing dams, irrigation, potable water, erosion control, wastewater, lightweight fill, mining, sports facilities, sludge dewatering, and many more in other fields.

Any situation that does not maximize the benefits of a class of materials/products should be of concern to that industry.

Q: Do you believe that civil engineers who are designing and specifying geosynthetics are educated and trained properly? What do you suggest that civil engineers do who are interested in advancing their education regarding this niche of the industry?

Peggs: Many are properly trained, but there are many who are not and who are responsible for the many failures that I investigate. This situation will get worse before it gets better due to the excessive demand for information that simply cannot be provided. Educational resources are moving to the Internet in an attempt to make information widely available and on demand (i.e., geosynthetica. net, Geosynthetics Institute courses, as well as others by the International Geosynthetics Society and the Geosynthetic Materials Association). In addition, engineers should attend conferences such as Geosynthetics 05 (in conjunction with GeoFrontiers 2005), the annual Geosynthetics Research Institute (GRI) conferences (this year held with GeoFrontiers 2005). They should subscribe to Geotextiles and Geomembranes, Geosynthetics International, and GFR, and they should purchase a copy of the book Designing with Geosynthetics by Robert Koerner. ASTM also has a number of special technical publications. Also, proceedings of the international and European geosynthetics conferences are available.

Q: Do you believe that the level of quality control during the manufacturing of geosynthetics products is acceptable? Have there been improvements in this arena worth mentioning? Are improvements required?

Peggs: Generally it is acceptable but, unfortunately, it cannot be relied upon. Last year I specified the resin to be used in a polypropylene geomembrane but I found another was used. The resulting geomembrane did not have the required mechanical properties, so it was rejected. A couple of years ago a quality control certificate showed the specified value, but it was measured at a low test temperature that provided optimistic results.

There is a tendency to assume that an order for a geomembrane is just the same as all of the others recently made, so specifications may not be read in detail. They must be and, if something different is noted, the manufacturer must determine whether the engineer intended it or if the engineer did not understand the departure from a conventional specification. The engineer could require that the manufacturer/installer sign a statement that all specifications have been reviewed and can be met. Then, if there is a problem, the responsibility to put it right rests solely with the manufacturer/installer.

Improvements have been made over the years with the GRI specifications that define the tests to be performed by the manufacturer and their frequency, including GRI.GM13 for high density polyethylene, GRI.GM17 for linear low density polyethylene, and GRI.GM18 for polypropylene. And now the Geosynthetic Institute is certifying products.

Q: Considering that geosynthetics is still a fairly new product category within the universe of construction materials, the long-term performance of many products still are being realized.Are there any recent, significant findings?

Peggs: The UK Environment Agency has just published a report on the durability of geomembrane landfill liners (R&D Technical Report P1- 500/1/TR, www.eareports.com) that is particularly useful.

Scott Thornton at TRI/Environmental has developed the Stepped Isothermal Method for developing creep curves and other long-term performance characteristics from short-term tests at stepped increasing temperatures; this is a rapid, modified, time-temperature superpositioning approach.

The Geosynthetic Institute standards for geomembranes include service temperature oxidation and ultraviolet resistance tests to complement the more rapid oxidative induction time tests at elevated temperatures for polyethylene and polypropylene geomembranes. Recent work is showing the effects on loss of additives by leaching and stress with resultant loss of oxidation and ultraviolet resistances in some materials. Others are performing well. We continue to investigate and understand these performance characteristics to maximize geosynthetic durability, no less than any other industry is doing.

Q: What exciting products and applications of geosynthetics are on the horizon for civil engineers? How significant do you believe their impact will be on the industry?

Peggs: While geomembranes for containment/barriers; geotextiles for separation, filtration, and cushioning; geonets for drainage; geogrids for reinforcement; and geocells for erosion control will become commodity items for commodity applications, out of them will grow specialty products. Examples include the following: bi- and tri-functional composites, smart products that will indicate points of overstress prior to failure, and electrokinetic geosynthetics that can move water around. The latter are being applied already for dewatering sludges and for accelerating the drainage of sports fields.

This clear commodity/specialty division will have a tremendous effect on the industry as the seeming complexity of geosynthetics is simplified for entry-level engineers within the commodity classification, yet there remain many challenges in the specialty field for experienced engineers. It also becomes easier, and safer, to transition from commodities to specialties. We all benefit.

However, the engineering community should not be waiting for these geosynthetics developments to occur. They must have some feeling for the problems that can be resolved with the use of geosynthetics and both the engineering and geosynthetics communities should work together to develop jointly what is possible for what is needed. This synergism should be further developed and maintained. Clearly there is also a reciprocal responsibility on the geosynthetics community to be in the field to identify unique challenges.

Q: From your work in failure analysis, have you noticed repeatedly a poor design method or manufacturing problem? 

Peggs: There are too many failures of retaining walls and landfill caps, and geosynthetics are being asked to perform functions of which they are incapable. While these appear to be failures of geosynthetics, they are actually failures in design. Walls and caps fail because inadequate drainage is provided. When an HDPE concrete basin liner swells, wrinkles, and welds/wrinkles crack in aromatic hydrocarbon and sulfuric acid solutions at over 60°C, it is not a failure of the HDPE, it is a failure of the design engineer who incorrectly specified HDPE for that application.

While HDPE is an excellent material, it is not the material for all applications, as many regulators and engineers seem to believe. It should not be specified simply because it is the easiest material to get approved by the regulator!

Education is the answer, but how to affect it is very difficult.

Ian Peggs, Ph.D., P.E., P.Eng., DABFET., founder and president of I-CORP International, Inc., cna be reached via email at icorp@geosynthetic.com

 

Sidebar: What Can The Geosynthetics Institute Do For You?
by George R. Koerner, PH.D., P.E., CQA

The Geosynthetic Institute (GSI) constitutes a diverse group of government agencies, owner/operators, consultants/testing laboratories, resin producers, manufacturers, and installers who actively promote the appropriate design and use of geosynthetics as engineering materials.The mission of GSI is to develop and transfer knowledge, to assess and critique geosynthetics, and to provide service to the member organizations and industry as a whole.

GSI was formed and incorporated in the state of Delaware on December 16, 1991. It is an independent, not-for-profit organization governed by an elected board of directors. It has a total of five separate but interrelated institutes under its umbrella.These five institutes include the following:

  • Geosynthetic Research Institute (GRI)
  • Geosynthetic Accreditation Institute (GAI)
  • Geosynthetic Education Institute (GEI)
  • Geosynthetic Information Institute (GII)
  • Geosynthetic Certification Institute (GCI)

Currently there are 61 member organizations of GSI. It is partially through their financial support that GSI conducts the following specific tasks:

  • conduct applied research on the engineering aspects of geosynthetics;
  • conduct basic research on resins, additives, fillers, and modifiers used to manufacture geosynthetics;
  • develop test methods, standards of practice, standard guides, and specifications for design and construction;
  • provide and implement geosynthetic accreditation and certification programs;
  • provide training and tutorial services to member organizations and their employees;
  • develop and provide courses, conferences, symposia,workshops, and training sessions;
  • provide geosynthetic information retrieval services;
  • provide publications in the form of newsletters, books,manuals, reports, journals, papers, articles, notes, and memos;
  • provide forensic services on both field successes and failures; and
  • develop a library of case histories involving geosynthetics and their behavior.

The GSI website (www.geosynthetic-institute. org) hosts many resources for both members and non-members, including generic specifications. Additionally, the GSI distributes CDs with select lectures on geosynthetic topics to the design community. The goal of the GSI is to be the conscience of the geosynthetic industry and to provide an ongoing center of excellence for all types of geosynthetics.

George R. Koerner, Ph.D, P.E., CQA, is the associate director of the Geosynthetic Institute.


Upcoming Events

See All Upcoming Events