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Résumé :
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Defect-free geomembrane liners can be considered impermeable to most landfill leachates so the objective of installing a geomembrane liner without holes and one that will remain intact throughout its design life is usually of paramount importance. Various types of defects, including holes arising prior to, during and after installation, and the reasons for their occurrence are considered. Post-installation liner failure can occur from environmental stress cracking, downdrag stresses caused by settling waste, folds, scratches and cuts subjected to stress, and penetration by items of waste, among other causes. The frequency of holes, taken from published data and from previously unpublished records of over 100 sites in the UK, is considered. The relevance of early (1980s) published data on hole frequency to present practice is addressed. Properties of manufactured sheet and tests of particular relevance to defect avoidance including environmental stress crack resistance, frictional properties and effectiveness of protection materials are discussed, together with the importance of careful design by the landfill engineer. Discussion on means of avoiding defects during installation and placement of cover materials addresses the benefits of construction quality assurance, leak location surveys and the importance of post-installation protection.
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