Geosynthetic Institute

Folsom, PA, United States

Geosynthetic Institute

Folsom, PA, United States
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Koerner R.M.,Geosynthetic Institute | Hsuan Y.G.,Drexel University | Koerner G.R.,Geosynthetic Institute
Geosynthetics International | Year: 2017

A very frequently asked question regarding all types of geosynthetics is, ‘How long will they last?' This paper answers the question for exposed geotextiles and geomembranes, assuming that they were properly designed and installed. Furthermore, it compares these new results to the earlier lifetime prediction results of a covered geomembrane. Nonexposed (or covered) lifetime conditions for a 1.5 mm thick high-density polyethylene (HDPE) geomembrane have previously been evaluated and published. Landfill incubation devices at four elevated temperatures of 85, 75, 65 and 55°C were used in the prediction in order to reach 50% of retained strength and elongation. Considering the three stages of (i) depletion of antioxidants, (ii) induction time, and (iii) 50% reduction in mechanical properties, the lifetime extrapolation was made down to 20°C. The 50% reduction value (called halflife throughout the paper) for this geomembrane under these conditions was approximately 450 years. Since the laboratory incubation times took 12 years, other nonexposed geosynthetics were not evaluated under the supposition that the covered situation is generally a moot point for most geosynthetics in their customary applications. For exposed (or uncovered) geosynthetics, however, the situation is quite different. Ultraviolet radiation, elevated temperature and full oxygen are available, which shortens the service lifetime, but how much? For evaluation of this situation, the authors utilized laboratory ultraviolet fluorescent tube weathering devices, as per ASTM D7238, for incubation purposes. Seven different geotextiles and five different geomembranes were evaluated. Each material was incubated at 80, 70 and 60°C until a 50% reduction of strength and elongation occurred. The data was then extrapolated down to 20°C for laboratory halflife values and for comparison with the nonexposed condition. The ratio of nonexposed to exposed lifetime for HDPE geomembranes is approximately seven. The calculations for the 12 exposed geosynthetics then progressed to using site-specific radiation to obtain an equivalent field halflife. Phoenix, Arizona, conditions are illustrated although the procedure is applicable worldwide. Halflife predictions for the geotextiles vary from a few months for the needle punched nonwovens to up to 10 years for monofilaments and high antioxidant formulated products. Results for geomembranes vary from 47 to 97 years, with HDPE being the highest. These exposed halflife results (which took 12 years of laboratory incubation to achieve) are felt to be most interesting and are presented for the first time to an international audience. © 2016 Thomas Telford Ltd.

Fourmont S.B.,Afitex Texel | Koerner G.R.,Geosynthetic Institute
Geotechnical Special Publication | Year: 2017

In the design and construction of landfill leachate collection and detection systems, it is important to maintain adequate drainage in order to minimize the hydraulic head on both primary and secondary liner systems. This is reflected in minimizing the leakage through the liner system. The situation is heightened when wet (also called bioreactor) landfilling is practiced in order to have rapid degradation of the organics as opposed to traditional dry landfilling. Concern has been expressed over such aggressive liquid management practices in bioreactor landfilling in regard to the long term clogging of geocomposites in either the leachate collection or leak detection systems of double lined municipal solid waste (MSW) landfills. In order to evaluate different geocomposite drainage systems we tested several per the GRI-GC1 Standard, "Test Method for Soil-Filter Core Combined Flow Test". These experiments were conducted for three years in a field laboratory at a major MSW landfill in the U.S.A. The investigation was conducted until system permeability reached equilibrium. It was found that the tubular geocomposite performed well over time. Good performance was predicated on proper geotextile filter selection with this particular leachate and set of environmental conditions. Conclusions and recommendations as to various possible drainage geocomposites and their behavior are presented. © ASCE.

Koerner G.R.,Geosynthetic Institute | Koerner R.M.,Geosynthetic Institute
Geotechnical Special Publication | Year: 2017

A most frequently asked question regarding all types of geomembranes is, "How long will they last?" This paper answers the question for exposed geomembranes assuming that they were properly designed and installed. Ultraviolet radiation, elevated temperature and full oxygen are available which shortens the service lifetime of a geomembrane. Ultraviolet fluorescent tube weathering devices per ASTM D7238 were used for incubation purposes. Five different geomembranes were evaluated. Each material was incubated at 80, 70, and 60°C until 50% reduction of strength and elongation occurred. The data was then extrapolated down to 20°C for laboratory halflife values and for comparison with the nonexposed condition. Results for geomembranes vary from 47 to 97 years with high density polyethylene (HDPE) being the highest. © ASCE.

Koerner R.M.,Drexel University | Hsuan Y.G.,Drexel University | Koerner G.R.,Geosynthetic Institute | Gryger D.,Gannett Fleming Inc.
Geotextiles and Geomembranes | Year: 2010

The need for a geotextile to be used for protection against geomembrane puncture by stones and gravel has been recognized for many years. There are presently several methods available for selecting such geotextiles. This paper, however, focuses on the " GRI-Method" , which was originally based on short-term tests and was extended empirically for long-term performance. The reduction factor for creep behavior (RFCR) is of particular interest since its impact on the resulting geotextile design is the greatest.The paper presents results of a 10-year long creep puncture study which is configured exactly the same as was the original short-term testing program. The results indicate that the six ≈38. mm high puncturing cones result in yield of the geomembrane at pressures of 34 and 52. kPa and one even had a small break. The six 12. mm high cones at pressures of 430 and 580 kPa also resulted in geomembrane yield but only by a nominal amount and there were no breaks.As a consequence of these creep test results, the original table for creep reduction factors (RFCR) has been revised into more conservative values. In this regard, the originally published RFCR table should be replaced accordingly. © 2010 Elsevier Ltd.

Wong W.-K.,Geosynthetic Institute | Hsuan Y.,Drexel University
Transportation Research Record | Year: 2012

This paper presents the interaction between carbon black and antioxidants in high-density polyethylene. The 11 formulations prepared for this study were composed of furnace black with particle sizes of 27 and 75 nm at 2% to 5% by weight and different concentrations of antioxidants Irganox 1010 and Irgafos 168. The chemical interactions between the carbon black and the antioxidants were accelerated by elevated temperatures of 85 C in a forced-air oven. The relative amount of antioxidants retained in the samples throughout the incubation was measured using the oxidative induction time (OIT) test. The results showed that the initial OIT value increased with the weight percentage of the carbon black in the sample. A higher initial OIT value was found in the samples that had been blended with the 27-nm carbon black than in those blended with the 75-nm carbon black at the same concentration. Also, faster OIT depletion was detected in the samples that had been blended with the 27-nm carbon black than in those blended with the 75-nm carbon black at greater than 2% by weight. The carbon black-antioxidant interaction was found to be influenced by the carbon black-specific surface area and physical structure. Overall, the OIT decreased substantially faster in the samples with carbon black than in those without it. The reactions between the carbon black and the antioxidants were so strong that only a minor difference in the depletion rate was observed between the two antioxidant formulations.

Koerner R.M.,Drexel University | Koerner G.R.,Geosynthetic Institute
Geotechnical Testing Journal | Year: 2010

There are two performance tests available for the selection of fabrics and additives when contemplating a geotextile bag, container, or tube application. They are the "hanging bag test" and the "pillow test." Both tests are described in this paper along with data generated by their use. While both can be used for selection purposes, the advantages of the pillow test over the hanging bag test are quite compelling. Items favoring the pillow test are much smaller size, need for less dredged or slurried infill material, better field simulated orientation, and the capability of monitoring hydraulic head versus time behavior. This last item is most important since dredging pressures are always involved and the simulated behavior of the pillow test gives good insight into the anticipated behavior of the full-scale application. Copyright © 2010 by ASTM International.

Koerner G.R.,Geosynthetic Institute | Koerner R.M.,Drexel University
Geotextiles and Geomembranes | Year: 2011

It is common practice to use needle-punched nonwoven geotextiles as puncture protection for geomembranes against sharp objects like gravel or stones in either the soil above or the underlying soil/rock below. There are several design and experimental methods available for geotextile selection in this regard. None, however, directly address the type of resin or fiber from which the geotextile is made. This paper does exactly that insofar as a direct comparison of similar mass per unit area polyester (PET) versus polypropylene (PP) geotextiles are concerned. Furthermore, two types of PP geotextiles are evaluated; one made from continuous filaments and the other from staple fibers. Three different size and shaped puncture probes are used in the testing program. All three are ASTM Standards, i.e., D4833, D5495 and D6241. The test results clearly indicate that geotextiles made from PP fibers outperform those made from PET fibers at all masses evaluated. Clearly, the present trend of using PP resin for heavy nonwoven protection geotextiles seems justified on the basis of these test results. In addition, the continuous filament PP and staple fiber PP geotextiles performed equivalently over all mass ranges for the three different types of puncture tests. © 2010 Elsevier Ltd.

Koerner R.M.,Geosynthetic Institute | Koerner G.R.,Geosynthetic Institute
Geotextiles and Geomembranes | Year: 2013

Following the introduction of mechanically stabilized earth walls with metallic reinforcement in 1966, polymeric reinforced structures (both geotextile and geogrid) followed shortly thereafter. A major item that accompanied this change in reinforcement type was the nature of the backfill soil. Corrosion of metallic reinforcement was no longer an issue with polymer-related geosynthetics and thus locally available fine-grained soils were generally used in place of quarried coarse-grained gravel soil. The cost savings are obvious as are the implications for concerns over inadequate performance. While failures have occurred in both types of reinforced walls, this paper focuses only on geosynthetic reinforced walls.This data base of 171 failed mechanically stabilized earth (MSE) walls with geosynthetic reinforcement includes 44 cases of excessive deformation and 127 cases of collapse of at least part of the wall. The large majority are located in North America and in the USA in particular. The main statistical findings are as follows:. 1.96% were private (as opposed to public) financed walls2.78% were located in North America3.71% were masonry block faced4.65% were 4-12m high5.91% were geogrid reinforced; the other 9% were geotextile reinforced6.86% failed in less than four years after their construction7.61% used silt and/or clay backfill in the reinforced soil zone8.72% had poor-to-moderate compaction9.98% were caused by improper design or construction (incidentally, none (0%) were caused by geosynthetic manufacturing failures)10.60% were caused by internal or external water (the remaining 40% were caused by internal or external soil related issues)In addition to presenting this statistical data, the paper also presents opinions and recommendations in several of the above areas particularly those which are felt to be at the core of why so many these structures are exhibiting performance problems. In general, the critical issues appear to be the following;. •fine grained silt and clay soils used for the reinforced zone backfill,•poor placement and compaction of these same fine grained backfill soils,•drainage systems and utilities being located within the reinforced soil zone,•non-existing water control either behind, beneath or above the reinforced soil zone, and•improperly determined and/or assessed design details.Concern over the situation has prompted the creation of an inspector's certification program, i.e., the Geosynthetic Certification Institute's-Inspector Certification Program (GCI-ICP) expressly for MSE walls, berms and slopes using geosynthetic reinforcement. © 2013 Elsevier Ltd.

Koerner G.R.,Geosynthetic Institute
Geotechnical Special Publication | Year: 2016

This paper describes ongoing research into the monitoring of two adjacent landfill cells with different liquids management strategies at an active municipal solid waste (MSW) landfill. One is a conventional dry cell and the other is a wet, or bioreactor, cell. To understand the waste materials behavior and associated geomembrane long-term behavior, the in-situ conditions are needed and how the various parameters change over time. In this regard, measurements have been taken at both cells for approximately 20-years and are continuing. Both dry and wet cells are monitored for changes in gases, leachate, waste and geomembrane temperatures. Knowing this information will allow for making longevity predictions in regard to both solid waste degradation and geosynthetics behavior. In addition, the data gives insight so as to fine-tuning the design-by-function approach for various situations and materials. © ASCE.

Koerner R.M.,Geosynthetic Institute
Geosynthetics | Year: 2012

All municipal solid waste (MSW) landfills require a final cover system placed over the waste mass within a relatively short period of time. In the U.S. this is within about one year. This final cover is maintained by the landfill owner or operator for 30 years, called the "post-closure care period." An alternative to this traditional final cover is to use an exposed geomembrane cover for the 30-year post-closure care period and then construct the final cover. There are many advantages to this alternative strategy, which are elaborated on in this article. This article also presents both a cost comparison and a sustainability comparison between the two alternatives. These comparisons reveal that the exposed geomembrane cost alternative is 30% of a traditional cover and the carbon footprint (based upon the amount of CO2 generated) for the exposed geomembrane alternative is only 18% of the traditional cover. A closing section is also included as to landfill strategies going beyond 30 years. A recent GSI survey shows that state regulatory agencies are uncertain in this regard. Two alternatives appear as follows: (a) If the traditional final cover is compromised because of the waste's large total and differential settlement, it must be removed; additional waste can be added, and then must be reconstructed. (b) When the exposed geomembrane cover has degraded it must be removed; additional waste can be added, and then a traditional final cover installed. These are, of course, site-specific situations and other possibilities exist as well. It appears as though a dialogue among the parties involved about various possible strategies beyond the 30-year post-closure care period would be worthwhile.

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