Barrier Technologies for Environmental Management Summary of a Workshop (1997) / Chapter Skim
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Geomembranes in Surface Barriers
Geomembranes in Surface Barriers
Pages 89-96
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From page 89... ...
The major concentration is to cover solid waste sites, liquid waste ponds, and potable water reservoirs, but numerous other applications such as odor containment, potential sabotage reduction, methane gas collection, and temporary waste covers are evident. The largest growing segment of the geomembrane industry has to do with cover systems tor solid waste containment.
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From page 90... ...
From a low percentage of use in 1981 to over 25 percent in 1988 and over 50 percent in 1995, semi-crystalline/low-crystallinity thermoplastic materials are outperforming competitive products for the following reasons: · relatively Tow cost wide extruded sheets wide variety of thicknesses wide variety of surface textures excellent chemical resistance reliable field welding (thermoplastic) good mechanical properties less field seams durability GEOMEMBRANE MANUFACTURE Most geomembranes are made in a manufacturing plant using one of the following highly technical and controlled manufacturing processes: extrusion, spread coating, and calendaring.
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From page 91... ...
Calendaring is the most frequently used manufacturing process. Calendared non-reinforced geomembranes usually consist of a single sheet of compound made by passing a heated polymeric component through a series of heated rollers (calendar)
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From page 92... ...
The bonding of two polymeric geomembranes results from an input of energy that originated from either thermal or chemical processes. There are generally four categories of seaming methods: extrusion welding, thermal fission (melt bonding)
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From page 93... ...
_ = cobbles/soil -l top layer biotic bamer (cobbles) drainage layer low hydraulic conductivity geomembrane/soil layer gas vent layer waste o ~ 0 Or ~ ~o D o 60 cm 30 cm geosynthetic filter geosynthetic filter 30 cm ~ geomembrane 60 cm geosynthetic filter FIGURE 3 EPA Recommended Cover System With Optional Layers (USEPA, 19911.
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From page 94... ...
, there are six separate primary mechanisms that can be attributed to geomembrane degradation over time by causing polymeric chain scission or bond breaking within the polymer structure: ultraviolet degradation radioactive degradation biological degradation chemical degradation thermal degradation oxidation degradation Any combination of the above mechanisms can cause synergistic effects due to interaction. addition, elevated temperatures and stress will accelerate any of the degradation processes.
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From page 95... ...
Thus, Arrhenius Modeling can be used for lifetime prediction using elevated temperature aging (Koerner, 1994~. The pipe and cable industry have used Arrhenius Modeling methodology extensively In the determination of in-service lifetimes for buried plastic pipe and cable, and much of this documented information is being used to model geomembrane aging characteristics.
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From page 96... ...
1991. Design and Construction of RCRA/CERCLA Final Covers, EPA Technical Guidance Document, EPA/625/4-91/025.
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