What are Geomembranes?
Geomembranes are synthetic, low-permeability liners or barriers, designed to control or prevent the migration of fluids and gases into the soil. They are typically formed into sheets and widely used in various applications such as landfills, pond liners, dams, erosion control, sediment control, and in the mining industry. Their primary function is to act as a barrier between the environment and potential contaminants.
Belonging to the broader category of Geosynthetics, geomembranes derive their name from “geo” meaning earth or soil, and “synthetic” referring to man-made materials. Geosynthetics are defined as planar, polymeric (either synthetic or natural) materials that interact with soil, rock, or other geotechnical substances for purposes such as filtration, drainage, separation, reinforcement, protection, sealing, and packing. Geosynthetics can be categorized into permeable membranes, like geotextiles, geogrids, and geocells, and impermeable membranes, such as geomembranes and geosynthetic clay liners (GCLs).
Difference Between Reinforced and Unreinforced Geomembranes
Reinforced
Geomembranes can be either reinforced with fabrics or unreinforced films. They typically range in thickness from 20 to 60 mils and possess properties like low permeability, low gas and water vapor transmission rates, chemical resistance, puncture resistance, and good weatherability. Unreinforced geomembranes are cost-effective, easy to install, and provide excellent chemical and UV resistance, making them suitable for less demanding applications like secondary containment liners, covers for wastewater treatment facilities, and decorative water features. They are also used in lining systems for temporary or short-term projects, such as storage ponds or construction sites.
Unreinforced
Reinforced geomembranes, on the other hand, offer durable performance and are cost-effective for a variety of civil and environmental engineering applications. The reinforcement layer, typically made of geotextile fabric, helps distribute and resist loading on the liner surface, enhancing the liner’s compressive and tensile strength. This makes reinforced geomembranes ideal for use in environments with uneven or settlement-prone substrates.
What are Geomembranes Made From?
Geomembranes are commonly made from polymers such as PVC, EIA, HDPE, and LLDPE. They are manufactured using methods like extrusion, calendaring, or spread coating. The properties of the polymers used significantly impact the design and specifications of the geomembrane for various project requirements. For example, the flexibility of the polymers can affect the installation process, while additives like antioxidants, carbon black, and UV packages can greatly extend the service life of the geomembrane. Geomembranes designed for exposed applications typically have a service life of around 30 years, though some can last much longer with minimal loss of physical properties.
For buried applications, geomembranes are often designed to protect against UV degradation, freezing, wind uplift, and damage from animals or humans, extending their service life well beyond 100 years. Thicker materials also contribute to a longer anticipated service life.
Types of Geomembranes and Their Properties:
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Type
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Abbreviation
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Polymer Type
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Typical Properties
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High-Density Polyethylene
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HDPE
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Thermoplastic
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High UV resistance, high chemical resistance, susceptible to stress cracking, difficult to install, unsupported only
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Linear Low-Density Polyethylene
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LLDPE
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Thermoplastic
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Good UV resistance, good chemical resistance, more flexible than HDPE, excellent elongation properties, reinforced and unsupported
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Polyvinyl Chloride
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PVC
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Thermoplastic
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Good flexibility at all temperatures, good chemical resistance, tear, puncture, and abrasion-resistant, can be prefabricated, susceptible to plasticizer loss, can be made UV stable, reinforced and unsupported
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Ethylene Interpolymer Alloy
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EIA
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Thermoplastic
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Good flexibility at all temperatures, high chemical resistance, tear, puncture, and abrasion-resistant, can be prefabricated, not susceptible to plasticizer loss, can be made UV stable, reinforced and unsupported
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