New GSI test method for resistance of conductive geosynthetics

June 1st, 2022

The Geosynthetic Institute (GSI) has a new test method for resistance measured across positions on conductive geosynthetics. Conductive geosynthetics contain an electrically charged backing (usually a thin layer of polyolefin with letdowns containing 20%–30% carbon black) that allows leaks to be detected in lined systems without the need for a conductive subgrade beneath the liner […]

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Geotextile filtration clogging resistance

February 1st, 2022

Q: I have a question about the Filter Criteria in the Federal Highway Administration (FHWA) procedure "Filter Performance and Design for Highway Drains" procedure, specifically the geotextile filtration clogging resistance equation 2-10. This seems to require a particularly large pore size; for example, if the D15 of the soil was for 70 microns, the minimum […]

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Sewn versus welded seams

February 1st, 2022

Q: On your GMA Techline website list of sample questions and answers, a question is asked about a recommendation for sewn versus welded seams for geotextiles. Bob Koerner answered this question by stating that you have done a study for joining geosynthetic clay liner (GCL) overlap seams via eight methods. Can you share that study […]

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EPDM geomembrane for a water application

February 1st, 2022

Q: We are looking at a life-cycle study for the usefulness of an ethylene propylene diene monomer (EPDM) geomembrane for a water conservation application. Request to kindly share the information for our study. Regards. A: An EPDM geomembrane is going to lie flat on the subgrade soil without wrinkles (no field-induced stress). Therefore, it will […]

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Geosynthetics for pipe wrapping

February 1st, 2022

Q: I need impervious geosynthetics for pipe wrapping that will be placed within heavy clay. Do you have any suggestions? A: One wraps nonpolymeric pipes for many reasons. Below are some examples: Insulation (sound and thermal)Corrosion protectionWaterproofingImpact resistance Most wraps are tapes or mastics. Polyvinyl chloride (PVC), butyl rubber and bituminous wraps are common. A […]

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Fusion-welded HDPE geomembrane patch

February 1st, 2022

Q: I need to make sure of what the minimum area is for a fusion-welded HDPE geomembrane patch with a 60-mil (1.5-mm) thickness that should be fusion welded instead of extrusion welded. Also, when does one need to replace a panel that is damaged (i.e., the percent of damage allowed to be repaired)? Thank you […]

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Electrical leak detection at depth

February 1st, 2022

Q: I am taking the opportunity to ask a question about the electrical leak detection (ELD) test for geomembranes:  We have the area covered with silt from the past rainy season, and it is estimated to be about 5 feet (1.5 m) deep worst-case scenario. The liners in this area were not properly inspected and […]

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ABS geosynthetics product types

February 1st, 2022

Q: Infrequently, I make a note of geosynthetic products manufactured using acrylonitrile butadiene styrene (ABS) (e.g., geogrid, binding line, a few molded specialty products). Can you provide a summary of most of the geosynthetic product types using ABS, as well as the general benefits and limitations of ABS geosynthetics? A: Thank you for your GMA […]

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Reinforced levees to induce seepage path around geogrid layers?

February 1st, 2022

FIGURE 1 Reinforced levee expansion over existing dike using geosynthetics The Geosynthetic Institute (GSI) has been asked many times regarding several applications for different styles of geogrids if reinforced levees will induce a seepage path adjacent to and around geosynthetic layers. At this point, GSI has no case histories where it can quantify such behavior […]

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Measuring strain in geosynthetics

October 1st, 2021

Q: Currently, what is the best-known method to measure strains in geosynthetics? We are having arguments between results generated from crosshead movement and extensometers. A: This question arises often when comparing ISO 527/ASTM D638 and ASTM D6693 results. The former requires an extensometer, where the latter utilizes crosshead deflection and assumes gauge lengths. This discussion […]

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