Gas diffusion coefficients

October 1, 2007

From the GMA Techline Subject: Gas diffusion coefficients— I am in the process of evaluating the mass flux of a gas moving through a 30-mil PVC geomembrane. I am working with volatile organic compounds in soils. What I need are typical values based on unsaturated soil vapors. I have found information on aqueous liquids but …

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HDPE welds

From the GMA Techline Subject: HDPE welds— For HDPE geomembranes, I am looking for information on what effect there might be, if any, on the integrity of a fusion weld when an extrusion weld is placed directly on top of it. This condition exists when completing patches at T-intersections, but there may be an occasion …

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Landfill liner installation inspection

From the GMA Techline Subject: Landfill liner installation inspection— I was hoping that maybe you would have information on training or certification on the inspection of installations of geomembrane liners for landfills. (Daniel, New York) Reply: We have the exact program you are looking for. It is called the Inspectors Certification Program, and it is …

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Polymer question

From the GMA Techline Subject: Polymer question— I would like to know if you can tell me which polymer is better to make nonwoven geotextiles, polyester or polypropylene? My problem is that I have to choose between two geotextiles with the same properties but with different polymers. (Ingrid, Honduras) Reply: Technically, each polymer has advantages …

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Geotextile compatibility

From the GMA Techline Subject: Geotextile compatibility— Is there any lab testing method or norm verifying the compatibility between polypropylene nonwoven geotextiles and shotcrete or concrete? Is ISO 12960 relevant? My question derives from my need to prove compatibility between this geotextile and material in contact in this project, such as shotcrete and a PVC …

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Effects of temperature on geomembrane strength

From the GMA Techline Subject: Effects of temperature on geomembrane strength— I am working on the design for some lined reservoirs where the liner may be exposed for some time during the summer, with the temperatures possibly approaching 120°F. We plan to use a 60-mil HDPE geomembrane. Giroud et al. advises that summer and winter …

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Access roads on HDPE liners

GMA techline answers from Bob Koerner Subject: Access roads on HDPE liners— I am designing a temporary waste storage facility that will be lined with a 1.5mm HDPE liner. The facility requires access roads for the life of the facility—18 months. The access roads will be installed directly above the liner (1.5mm HDPE) and protective …

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Geomembrane wrinkles during installation

From the GMA Techline Subject: Geomembrane wrinkles during installation— What is the general state of practice for limiting wrinkles during geomembrane installation? What is the maximum wrinkle height that should be allowed? Should it be trapped straight up or allowed to fold over? Thanks. (Ernest, New York) Reply: Years ago, I thought that small wrinkles …

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Geotextile cushion design

From the GMA Techline Subject: Geotextile cushion design— Using the geotextile cushion calculator on landfilldesign.com, and according to your research report, we should be using a factor of safety of 3 for cushion geotextile and the size of the protrusion height at half the height of the largest particle of gravel used for the Linear …

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Geotextile for base stability

From the GMA Techline Subject: Geotextile for base stability— I am a landscape architect and value your Geosynthetics publication in my practice. While reading the June/July issue [and the article on] roads and housing on wet soils, a current project challenge of mine came to light: How to best provide base stability to a proposed …