Factors Influencing Material Selection
There are various factors that determine the suitable material for a particular application. Some key factors are lifetime requirements, site conditions, waste type, mechanical stresses etc. HDPE and LLDPE geomembranes can last over 50 years and are resistant to punctures. They are suitable for landfill capping and lining. PVC has good heat resistance but may degrade due to UV exposure over time. EPDM is flexible even at sub-zero temperatures but expensive. The material should maintain its physical and chemical integrity for the intended design life of the project.
Key Properties
They should have certain key properties to function effectively as barriers. They should be impermeable to fluids and gasses. The permeability rate should be less than 1x10-12 cm/s. They should have high tensile strength (15-30 MPa) to withstand stresses from waste settlement, machinery movement etc. Puncture and tear resistance is also important as punctures can lead to leakage. Flexibility allows them to deform and adapt to ground movements without cracking. Resistance to weathering, chemical attacks, biological reactions etc ensures long service life. Today high performance Geomembrane meet demanding specifications through advanced manufacturing processes.
Installation
Proper installation and testing methods are vital for them to deliver the expected performance. The subgrade requires leveling and compaction to provide a stable base. The rolls are overlapped and heat welded together. Non-destructive tests like air pressure tests are done to locate any defects. Ancillary materials like protective layers, leak detection systems and drainage layers provide further protection. Prefabricated components like sumps integrate for added reinforcement. Modern techniques using GPS and digital mapping ensure them are installed accurately as per the design. Quality assurance during installation and testing enables robust barrier systems.
Applications in Waste Management
They play a crucial role in waste containment facilities preventing contamination. In a landfill, a compacted soil liner is covered with a flexible membrane liner or composite liner system. This forms the primary barrier restricting leakage from landfilled waste. Similarly, they are used to line leachate collection ponds and landfill gas collection systems. For hazardous waste sites, double or triple liner systems with leak detection layers provide enhanced protection. They effectively isolate stored wastes when combined with leachate collection/removal systems. This facilitates safe waste disposal practices according to environmental regulations.
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