Manufacturing
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 byProperties
The majority of generic geomembrane test methods that are referenced worldwide are by the ASTM International, American Society of Testing and Materials (Physical properties
The main physical properties of geomembranes in the as-manufactured state are: * Thickness (smooth sheet, textured, asperity height) * Density * Melt flow index * Mass per unit area (weight) * Vapor transmission (water and solvent).Mechanical properties
There are a number of mechanical tests that have been developed to determine the strength of polymeric sheet materials. Many have been adopted for use in evaluating geomembranes. They represent both quality control and design, i.e., index versus performance tests. * tensile strength and elongation (index, wide width, axisymmetric, and seams) * tear resistance * impact resistance *Endurance
Any phenomenon that causes polymeric chain scission, bond breaking, additive depletion, or extraction within the geomembrane must be considered as compromising to its long-term performance. There are a number of potential concerns in this regard. While each is material-specific, the general behavior trend is to cause the geomembrane to becomeLifetime
Geomembranes degrade slowly enough that their lifetime behavior is as yet uncharted. Thus, accelerated testing, either by high stress, elevated temperatures and/or aggressive liquids, is the only way to determine how the material will behave long-term. Lifetime prediction methods use the following means of interpreting the data: * ''Stress limit testing:'' A method by the HDPE pipe industry in the United States for determining the value of hydrostatic design basis stress. * ''Rate process method:'' Used in Europe for pipes and geomembranes, the method yields similar results as stress limit testing. * ''Hoechst multiparameter approach:'' A method that utilizes biaxial stresses and stress relaxation for lifetime prediction and can include seams as well. * ''Arrhenius modeling:'' A method for testing geomembranes (and other geosynthetics) described in Koerner for both buried and exposed conditions.Seaming
The fundamental mechanism of seaming polymeric geomembrane sheets together is to temporarily reorganize the polymer structure (by melting or softening) of the two opposing surfaces to be joined in a controlled manner that, after the application of pressure, results in the two sheets being bonded together. This reorganization results from an input of energy that originates from either ''thermal'' or ''chemical'' processes. These processes may involve the addition of additional polymer in the area to be bonded. Ideally, seaming two geomembrane sheets should result in no net loss of tensile strength across the two sheets, and the joined sheets should perform as one single geomembrane sheet. However, due to stress concentrations resulting from the seam geometry, current seaming techniques may result in minor tensile strength and/or elongation loss relative to the parent sheet. The characteristics of the seamed area are a function of the type of geomembrane and the seaming technique used.Applications
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.See also
* Electrical liner integrity surveyReferences
Further reading
# ICOLD Bulletin 135, ''Geomembrane Sealing Systems for Dams'', 2010, Paris, France, 464 pgs. # August, H., Holzlöhne, U. and Meggys, T. (1997), ''Advanced Landfill Liner Systems'', Thomas Telford Publ., London, 389 pgs. # Kays, W. B. (1987), ''Construction of Linings for Reservoirs, Tanks and Pollution Control Foundation'', J. Wiley and Sons, New York, NY, 379 pgs. # Rollin, A. and Rigo, J. M. (1991), ''Geomembranes: Identification and Performance Testing'', Chapman and Hall Publ., London, 355 pgs. # Müller, W. (2007), ''HDPE Geomembranes in Geotechnics'', Springer-Verlag Publ., Berlin, 485 pgs. # Sharma, H. D. and Lewis, S. P. (1994), ''Waste Containment Systems, Waste Stabilization and Landfills'', J. Wiley and Sons, New York, NY, 586 pgs. {{Geotechnical engineering Geosynthetics Building materials Landfill