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The GMA Techline

October 1, 2018

Toxicity of nonwovens? Q: Are there any comprehensive tests (or a general synopsis) of the environmental toxicity of leachate from nonwoven polypropylene fabrics when aged in a freshwater or saltwater solution? Regulatory and municipal bodies in Europe and New Zealand are requesting more info about products that are used in riparian and coastal environments. A: …

Geosynthetics opportunities and solutions in shale gas extraction

While natural gas contained within shale rock is geologic and thus ancient by its very nature, the practice of its removal by horizontal drilling coupled with hydrofracking is a relatively recent development (Figure 1). Indeed, these dual technologies are making possible the recovery of huge amounts of natural gas—so much so that one can envision …

Don’t be afraid of making horizontal geomembrane seams on side slopes

August 1, 2018

Over the years, there have been many discussions raising concerns about having geomembrane field seams located horizontally on side slopes. By not allowing such seams, it usually results in many short roll lengths that become either unused or difficult to tailor into the flat area of the project. Stated differently, the installation costs increase accordingly. …

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UV Weathering of Geotextiles Q: My firm is providing construction quality assurance services for a landfill cell expansion. We are having an issue with our contractor and are going to be in a position of having 8 ounces/square yard (271 g/m2) of nonwoven geotextile exposed for a period of time, which exceeds the seven-day limit …

Estimating live loads in MSE wall and slope design

June 1, 2018

In formulating a factor-of-safety value for a mechanically stabilized earth (MSE) wall or slope project, a design engineer calculates a ratio of resisting forces to driving forces. This contrast is further recognized when using load and resistance factor design (LRFD), which is in our not-too-distant future. The resisting forces are the soil’s inherent properties (e.g., …

Commentary on attribution and referencing in technical papers

April 1, 2018

In presenting written technical information in academic papers and presentations, including in geosynthetic papers, as well as conference proceedings and presentations, it is established practice for the author to attribute references, data, charts, tables, graphs, photographs, illustrations and concepts back to the initial originator/developer, who under law is the copyright holder to the work simply …

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GMA Techline

February 1, 2018

Determining quantity of recycled HDPE in a geonet Q: I have a question about high-density polyethylene (HDPE) geonets. Is it possible, by thermogravimetric analysis (TGA) and differential scanning calorimeter (DSC) analysis, to determine the quantity of recycled HDPE present in a geonet? I have a geonet that, I think, is made with virgin and recycled …

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The durability of exposed geomembrane covers

October 1, 2017

The most frequently asked question by people in the geosynthetics world is how long is the anticipated lifetime of geosynthetics. So much so that of the more than 3,000 questions submitted to the GMA Techline since it began in 2004, 591 (19.7%) have been on lifetime, aka durability. Of these, 49% were on buried lifetime, …

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GMA Techline

Welding HDPE to PVC and more Q: I would appreciate any input you have on these questions: Can a high-density polyethylene (HDPE) geomembrane (GM) be welded to a PVC geomembrane? I am looking to connect a geomembrane to a building foundation. Based on some research, I have found the following options: bolt the geomembrane to …

Geosynthetic Institute news: Mega waterbags

According to the United Nations (UN), 1.1 billion people in 34 countries have inadequate access to safe drinking water. Furthermore, pollution, global warming and population growth will have continuing negative impacts on the availability of safe drinking water. By the year 2040, the UN estimates that more than 2 billion people in 60 countries will …