Geomembrane: A Synthetic Liner for Containing Liquids and Preventing Contamination
Geosynthetics are synthetic membrane liners made of polymeric materials that function as barriers. When placed between environmental media such as soil, rock, and water, geosynthetics are able to contain liquids and prevent contamination from passing between the separated materials. Typical uses of geosynthetics include applications in infrastructure projects like landfills, mining operations, and hydraulic structures.
Composition and Manufacturing
The most common geosynthetics are made from polyethylene (PE). There are two main types - high-density polyethylene (HDPE) which is rigid and low-density polyethylene (LDPE) which is flexible. Other polymers used include polyvinyl chloride (PVC), polypropylene (PP), and ethylene propylene diene monomer (EPDM) rubber.
Sheets of these materials are manufactured through techniques like extrusion, calendaring, and spinning. Extrusion is the most widely used method where the molten polymer is continuously squeezed through a die to form a thin, wide sheet. Quality control measures ensure geosynthetics meet specifications for thickness, density, tear resistance, puncture resistance and hydrostatic resistance.
Seaming and Installation
At installation sites, Geomembrane sections are seamed together through thermal or chemical bonding techniques. Hot air or infrared welds are commonly used to thermally bond HDPE and PP while solvent or adhesive welding joins PVC. Mechanical connection devices like steel strips can also seam geosynthetics.
Proper subgrade preparation, anchor trench construction and non-woven geotextile cushion layers are required before rolling out the geosynthetic. Its sides and edges need to be securely fixed to retain the contained materials. Care is taken to avoid damage from site equipment, rocks or other sharp elements during and after installation.
Applications in Infrastructure Projects
Landfill Liners
The primary use of geosynthetics is in landfill lining applications. As the bottom and side liner, they isolate deposited waste from surrounding soil and groundwater. This prevents leachate (contaminated liquid) from seeping out of landfills into the environment.
Mining Liners
In both surface and underground mining operations, geosynthetics are used to contain process water, residue slurries from mills, and runoff/seepage from waste rock piles or tailings dams. This protects soil and water near mines from toxic contamination by heavy metals and acidic mine drainage.
Canals and Reservoirs
When constructing new water storage reservoirs or canal lining projects, geosynthetics function as waterproof membranes. They maintain water levels and quality by preventing leakage. Geosynthetics allow existing earthen canals to be rehabilitated without more costly concrete relining.
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