A new specification for geotextile grout filled mattresses

April 1st, 2021

By George R. Koerner FIGURE 1 GGFM being filled incrementally. Courtesy of HUESKER Geotextile grout filled mattresses (GGFM), also referred to (in ASTM D18.25/D35.05) as fabric-formed concrete (FFC) or fabric-formed concrete revetments (FFCR), are erosion-resistant concrete linings made from durable, permeable fabric forms that are filled with high-strength grout. GGFMs are generally sloping structures placed […]

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GMA Techline: Anchors, tie-rods and whalers

April 1st, 2021

Q: We are having issues related to obstructions in the reinforced zone of our mechanically stabilized earth (MSE) retaining walls. In the first case, there is a rock outcrop that is limiting the length of the geogrid reinforcement. In the second case, we have a drop-down inlet structure to divert stormwater, which is in the […]

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GMA Techline: Geomembranes for reinforcement?

April 1st, 2021

Q: We are using Robert Koerner’s Designing with Geosynthetics to calculate the required thickness of a geomembrane. See Figure 1 and Equation 1 from the book for details. Figure 1 Equation 1 Can you point us in the right direction with the mobilization distance, x? A: Yes, please see Figure 2 for high-density polyethylene (HDPE). […]

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GMA Techline: Installing a geomembrane low to high gradient?

April 1st, 2021

Q: We are a large liner installation firm that has been asked to install a geomembrane liner from low gradient to high gradient. Is this the new normal? A: This is not normal, and we suggest you strongly object to this recommendation. There are many stakeholders in regard to panel layout (i.e., installer, general contractor, […]

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GMA Techline: GRI-GM19 peel specification

April 1st, 2021

Q: Our liner system is a double composite and along a western tie-in. We need to extrusion-weld the secondary 60-mil (1.5-mm) HDPE (new cell) to an existing secondary 40-mil (1-mm) HDPE (old cell), and the state is continuing to have issues with the fact that we are using the 40-mil (1-mm) GRI-GM19 peel specification as […]

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GMA Techline: Concrete interlayers

April 1st, 2021

Q: We are interested in using a geotextile as an “unbonded concrete interlayer” over existing concrete pavement to float the new slab over deteriorated pavement, instead of a thin asphalt layer. Do you have any guidance for us in this regard? A: Over the past several years, 16-ounce-per-square-yard (542-g/m2) nonwoven needlepunched geotextiles have been used […]

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The GMA Techline

February 1st, 2021

Moderated by George R. Koerner BIOLOGICAL DEGRADATION OF PE AND PP Q: Can you please enlighten me on the biological degradation of polyolefin polyethylene (PE) and polypropylene (PP)? A: Within the various plant forms of biological life, i.e., bacteria, actinomycetes, fungi and algae, polymer degradation is essentially nonexistent due to high molecular weight of the common […]

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Extreme direct shear testing

February 1st, 2021

By George R. Koerner The Geosynthetic Institute (GSI) is doing direct shear testing under extreme environmental conditions (i.e., specifically extreme temperatures). At the prompting of two member companies, we have initiated an effort in this regard. This work looks at response curves over a wide range of normal pressures, 0–43.5 psi (0–300 kPa). The work […]

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Testing wind-resistant geosynthetics

October 1st, 2020

By George R. Koerner As you can see by Figure 1, we are experiencing a new age of geosynthetics. Over the past 15 years, we have seen a propensity of polymeric materials left exposed to rather than covered from the environment. This is in large part due to the strides geosynthetic manufacturers and polymer formulators […]

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The GMA Techline

October 1st, 2020

Moderated by George R. Koerner Puncture after NDT Q: I would like your opinion on the fate of punctures in the air channel leftover from nondestructive air channel tests (NDTs), specifically in regard to sealing the air channels to prevent leachate or water ingress. We are particularly concerned with this situation on a landfill cover […]

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