Design of a CCR composite liner system

August 1st, 2021

Q: We are designing a composite liner system for a coal ash landfill. From the bottom-up, the cross section is subgrade soil, geosynthetic clay liner (GCL), geomembrane, composite drainage layer with nonwoven geotextiles on both sides and then ash from coal combustion residuals (CCR). Do you have an opinion on the design, particularly on 3:1 […]

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A geotextile filter for an edge drain

August 1st, 2021

Q: I am doing a geotextile filter design for a highway edge drain. All I have from the site is a grain size analysis of the sandy subgrade soil. Can you point me in the right direction? A: First you are going to need to calculate an estimate of hydraulic conductivity for the sandy soil […]

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Bluff repair in seismically active zone

August 1st, 2021

Q: I am doing a bluff repair on the West Coast in a seismically active zone. Can you direct me to where I can get some design guidance? A: The following references are excellent in regard to your question. National Concrete Masonry Association. (2009). “Guidelines for the design and analysis of mechanically stabilized earth (MSE) […]

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Service life of nonwovens

August 1st, 2021

Q: Where can I find literature on the useful service life of nonwoven geosynthetic fabrics installed in soils? A: One of the best references in this regard is from a manufacturer of nonwoven geotextiles. It is:  SI Geosolutions (now Propex). (1997). Smart Solutions, Technical Note, SM-404. “The durability of polypropylene nonwoven geotextiles for waste containment […]

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Metal leaching from geosynthetics

August 1st, 2021

Q: Geosynthetics are made from polymers that use metal-based catalysts in their formulations. Do geosynthetics have the potential to leach metals into the environment? A: I think the fair answer to this is yes, but the potential risk is very small due to the long-term stability of the polymers used in geosynthetics and the very […]

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Bringing geomembranes into equilibrium with atmosphere

August 1st, 2021

Q: Some ASTM test methods request that one brings the specimens into equilibrium with the atmosphere prior to the test (some of them determine the conditions: 21±2ºC and 60±10% relative humidity). Considering that we just produce polyethylene geomembranes, and they are not significantly affected by the relative humidity, do you have any suggestions about how […]

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GSI’s new GCL test method

August 1st, 2021

The Geosynthetic Institute (GSI) has a new standard test method for “Determination of the Polymer Loading in Geosynthetic Clay Liners (GCLs).” It was developed over several years without consensus of the membership. GSI forged ahead with it because we see many such products in the market and believe there is a need to start the […]

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OIT for UV and oven aging

June 1st, 2021

Q: I am contacting you in regard to the requirements for oxidative induction time (OIT) (standard [STD] and high pressure [HP]) in the GRI-GM13 specification for both ultraviolet light and oven aging. Do you need to conduct both OIT tests or just one or the other? A: I would strongly recommend reading the EuroGeo 4 […]

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Geotextile under articulated systems in slope armoring

June 1st, 2021

Q: I have a question about the geotextile placed under articulated systems in slope armoring. Based on my understanding, a drainage layer is recommended between the geotextile and the armoring structure, but, since the armoring structure has some spaces in between the armoring blocks, won’t the particles of the drainage layer be washed out through […]

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Industry standard for wall drainage systems?

June 1st, 2021

Q: I just watched your recorded video of mechanically stabilized earth (MSE) wall inspection. Thank you for the presentation; it was very informative. I do have a follow-up question for you. I was recently the site engineer for a precast panel MSE wall and now have the opportunity to inspect construction of the wall that […]

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