GMA techline

> Email the GMA Techline

The Geosynthetic Materials Association (GMA) offers the GMA Techline, a resource for technical questions about geosynthetics. E-mail: gmatechline@ifai.com for fast, free, direct answers to your technical questions.

GMA serves as the central resource for information regarding geosynthetics and provides a forum for consistent and accurate information to increase the acceptance, and to promote the correct use, of geosynthetics.

Browse the entries below list to find past answers highlighted in Geosynthetics magazine.

Page 1 of 7 (102 results total)

  • Floating covers

    February 1, 2013

    Designing and installing a floating roof cover to a circular concrete reservoir.

  • Geomembrane leakage rates

    February 1, 2013

    Leak detection system data for geomembrane liners.

  • Geotextile compatibility w/typical MSW landfill leachate

    February 1, 2013

    A question on geotextile and geomembrane compatibility with typical landfill leachate.

  • Plastic connections

    February 1, 2013

    Recommendations for plastic connectlons to insert into concrete blocks.

  • Reinforced geomembrane seams

    February 1, 2013

    Where to find the typical requirement for the seaming of reinforced geomembranes.

  • Geogrid lateral load

    January 28, 2013

    Typical design codes include a routine for surcharge and many static and dynamic loads as well.

  • GCL and HDPE questions

    June 1, 2012

    GCLs do not whale up from pressures, and HDPE pipe crushes when overstressed.

  • High-temp resilient liner

    June 1, 2012

    The highest that geomembrane manufacturers recommend for usage is between 150–170 F.

  • MSE wall connection

    June 1, 2012

    Connection of geosynthetic reinforcement can be either mechanical or frictional.

  • MSW landfill cap anchor trench design

    June 1, 2012

    With landfill anchor trenches, normal stress would be higher but the approach is the same.

  • Peak friction values for textured HDPE

    June 1, 2012

    You have to test the interface of the specific HDPE-T with the specific NW-NP fabric.

  • Polypropylene vs. polyester

    June 1, 2012

    From the very beginning of geotextiles, polyester (PET) and polypropylene (PP) fibers and filaments have been competitive for the manufacturing of nonwoven fabrics.

  • Question about AOS

    June 1, 2012

    AOS is an empirical value that can only be assessed in light of the test method itself.

  • Comparing GCLs

    October 1, 2011

    A reader needs some assistance in comparing two geosynthetic clay liners for a project.

  • Draping and spraying

    October 1, 2011

    Reader seeks geosynthetic fabric webbing or netting to be draped and sprayed with concrete.

  • Drainage and filter components for green roofs

    Sponsored by IFAI Expo

    The Purpose of Drainage for Green Roofs

    • Manage rainfall without sustaining damage from erosion/ponding of water
    • Provides void space and slope to transport subsurface water
    • Connects to roof drains, gutters, and scuppers and conducts water away from roof
    • Removes surface water from impervious surfaces
    • Maintains optimum growing conditions in the planting media

    The Purpose of Filter for Green Roofs

    • To prevent fine planting media particles from washing into the drainage layer
    • Prevents the reduction or clogging of drainage capacity
    • Usually a nonwoven geotextile, occasionally a woven fabric, is used

    Filter Components
    For retention:

    • The geotextile must have small enough openings to adequately retain the planting media
    • If not, soil particles will eventually clog the drain core

    For permeability:

    • The geotextile must have large enough openings to allow unimpeded flow of water
    • If not, hydrostatic pressure will build up and the planting media will not drain

    What are Geocomposite Drains?

    • A manufactured material that combines geotextiles and a polymeric core
    • The core composition varies in design and material
    • Geotextiles may be applied to one or both sides using heat bonding or adhesives
    • Geotextiles can filter, protect or hold water
    • Geotextiles are available in sheets or rolls that are overlapped or joined during construction

    Source: “How to Design Green Roofs & Landscapes” presented at the 2009 IFAI Expo, Sept. 22, 2009, in San Diego, hosted by the Geosynthetic Materials Association (GMA)