A geomembrane is very low permeability synthetic membrane liner or barrier used with any geotechnical engineering related material so as to control fluid (or gas) migration in a human-made project, structure, or system. Geomembranes are made from relatively thin continuous polymeric sheets, but they can also be made from the impregnation of geotextiles with asphalt, elastomer or polymer sprays, or as multilayered bitumen geocomposites. Continuous polymer sheet geomembranes are, by far, the most common.
The manufacturing of geomembranes begins with the production of the raw materials, which include the polymer resin, and various additives such as antioxidants, plasticizers, fillers, carbon black, and lubricants (as a processing aid). These raw materials (i.e., the "formulation") are then processed into sheets of various widths and thickness by extrusion, calendering, and/or spread coating.
Three methods used to manufacture geomembranes.
Geomembranes dominate the sales of geosynthetic products, at 1.8 billion USD per year worldwide, which is 35% of the market.
The US market is currently divided between HDPE, LLDPE, fPP, PVC, CSPE-R, EPDM-R and others (such as EIA-R), and can be summarized as follows:(Note that M m2 refers to millions of square meters.)
The majority of generic geomembrane test methods that are referenced worldwide are by the ASTM International|American Society of Testing and Materials (ASTM) due to their long history in this activity. More recent are test method developed by the International Organization for Standardization (ISO). Lastly, the Geosynthetic Research Institute (GRI) has developed test methods that are only for test methods not addressed by ASTM or ISO. Of course, individual countries and manufacturers often have specific (and sometimes) proprietary test methods.
The main physical properties of geomembranes in the as-manufactured state are:
Thickness (smooth sheet, textured, asperity height)
Melt flow index
Mass per unit area (weight)
Vapor transmission (water and solvent).
Geomembrane installation as part of the construction of a base liner system of a landfill.
Geomembranes have been used in the following environmental, geotechnical, hydraulic, transportation, and private development applications:
As liners for potable water
As liners for reserve water (e.g., safe shutdown of nuclear facilities)
As liners for waste liquids (e.g., sewage sludge)
Liners for radioactive or hazardous waste liquid
As liners for secondary containment of underground storage tanks
As liners for solar ponds
As liners for brine solutions
As liners for the agriculture industry
As liners for the aquiculture industry, such as fish/shrimp pond
As liners for golf course water holes and sand bunkers
As liners for all types of decorative and architectural ponds
As liners for water conveyance canals
As liners for various waste conveyance canals
As liners for primary, secondary, and/or tertiary solid-waste landfills and waste piles
As liners for heap leach pads
As covers (caps) for solid-waste landfills
As covers for aerobic and anaerobic manure digesters in the agriculture industry
As covers for power plant coal ash
As liners for vertical walls: single or double with leak detection
As cutoffs within zoned earth dams for seepage control
As linings for emergency spillways
As waterproofing liners within tunnels and pipelines
As waterproof facing of earth and rockfill dams
As waterproof facing for roller compacted concrete dams
As waterproof facing for masonry and concrete dams
Within cofferdams for seepage control
As floating reservoirs for seepage control
As floating reservoir covers for preventing pollution
To contain and transport liquids in trucks
To contain and transport potable water and other liquids in the ocean
As a barrier to odors from landfills
As a barrier to vapors (radon, hydrocarbons, etc.) beneath buildings
To control expansive soils
To control frost-susceptible soils
To shield sinkhole-susceptible areas from flowing water
To prevent infiltration of water in sensitive areas
To form barrier tubes as dams
To face structural supports as temporary cofferdams
To conduct water flow into preferred paths
Beneath highways to prevent pollution from deicing salts
Beneath and adjacent to highways to capture hazardous liquid spills
As containment structures for temporary surcharges
To aid in establishing uniformity of subsurface compressibility and subsidence
Beneath asphalt overlays as a waterproofing layer
To contain seepage losses in existing above-ground tanks
As flexible forms where loss of material cannot be allowed.
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