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Reinforced levees to induce seepage path around geogrid layers?
February 1st, 2022
FIGURE 1 Reinforced levee expansion over existing dike using geosynthetics The Geosynthetic Institute (GSI) has been asked many times regarding several applications for different styles of geogrids if reinforced levees will induce a seepage path adjacent to and around geosynthetic layers. At this point, GSI has no case histories where it can quantify such behavior […]
Heat resistance of geomembranes
October 1st, 2021
Q: We have a question in regard to the heat resistance of geomembranes. We are interested in paving a road over a geomembrane with hot mix asphalt and want to know if the geomembrane will continue to function as a moisture barrier? A: The answer to this depends very much on the formulation from which […]
Repeatability and reproducibility in geosynthetics
October 1st, 2021
Q: If repeatability and reproducibility are high, it is a positive output, but high repeatability and reproducibility will give high uncertainty from Equation 1: uncertainty = sqrt (repeatability^2 + reproducibility^2) Could you explain to me why it looks like it is contradictory? A: One wishes to have the repeatability and reproducibility as “low” as possible, […]
Measuring strain in geosynthetics
October 1st, 2021
Q: Currently, what is the best-known method to measure strains in geosynthetics? We are having arguments between results generated from crosshead movement and extensometers. A: This question arises often when comparing ISO 527/ASTM D638 and ASTM D6693 results. The former requires an extensometer, where the latter utilizes crosshead deflection and assumes gauge lengths. This discussion […]
Residual strength of a geosynthetic clay liner
October 1st, 2021
Q: I was wondering if I could get some input about the residual strength of a geosynthetic clay liner (GCL). We have lab results where it is “flatlining” for the residual case (Figures 1 and 2, and Tables 2–4). The GCL is proposed for use in a landfill cell with ultimately a maximum of 98 […]
New anchorage and connection strength tests for geosynthetics
October 1st, 2021
FIGURE 1 Field anchor pullout test Connections can have a significant impact on the performance of exposed geosynthetic systems. The connection must be considered as a limiting strength factor and evaluated by the same performance standards as the material alone. If used in critical structures with design lives of more than 30 years, the geosynthetic […]
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 […]
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 […]
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 […]
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 […]