GCL-GM geocomposite: Which end is up?

April 1, 2022  |  Q&A: GMA Techline

Q: In a geosynthetic clay liner-geomembrane (GCL-GM) geocomposite, does it make any difference which side of the geocomposite is up: GM or clay?
Calendared nonwoven geotextiles

April 1, 2022  |  Q&A: GMA Techline

Q: What is the difference between normal nonwoven and calendared nonwoven (both needlepunched) geotextiles? Where can we use calendared nonwoven geotextiles?
LCC curing effect on geogrids

April 1, 2022  |  Q&A: GMA Techline

Q: Can you tell me whether modest warming of geogrids (e.g., due to heat generated by the curing of lightweight cellular concrete [LCC]) might impact the long-term strength or long-term modulus of geogrids?
High pH effects geogrids?

April 1, 2022  |  Q&A: GMA Techline

Q: Can you tell me whether the high pH of curing portland cement (typically ~12.4) might have any impact on the long-term performance of geogrids?
Methane gas geomembrane permeability

April 1, 2022  |  Q&A: GMA Techline

Q: What is the least permeable geomembrane to methane gas? Regarding the permeability of geomembranes to methane gas, could you send me some technical guidelines?
Scratch impact on HDPE liners

April 1, 2022  |  Q&A: GMA Techline

Q: I have a project where multiple and extensive scratches were created on the high-density polyethylene (HDPE) liner for a reservoir due to poor construction practices. (See the following Figures 2–4.)
Sand fines overlying geocomposite

April 1, 2022  |  Q&A: GMA Techline

Q: We are working at a site with a permitted landfill cell with a leachate collection system that includes a drainage geocomposite with 12 inches (305 mm) of leachate collection sand overlying it. My question has to do with the percentage of fines in sand on a geocomposite. Our leachate collection p…
Electrical leak detection at depth

February 1, 2022  |  Q&A: GMA Techline

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 inspect…
ABS geosynthetics product types

February 1, 2022  |  Q&A: GMA Techline

Q: Infrequently, I note 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…
Geotextile filtration clogging resistance

February 1, 2022  |  Q&A: GMA Techline

Q: I have a question about the Filter Criteria in the Federal Highway Administration (FHWA) Filter Design procedure, specifically the 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 O95 of th…