A geosynthetic clay liner (GCL) is a low permeability layer that is often used as part of a composite liner in various hydraulic barrier applications, such as landfills. The GCL consists of bentonite, a high swelling clay, that is bonded to other geosynthetic layers by needle punched fibres or epoxy. After placement of the liner on a foundation soil, the bentonite must hydrate by absorbing water from the subsoil in order to achieve a homogeneous structure and its low hydraulic conductivity. However, if these GCLs subsequently lose moisture, the internal bentonite layer is susceptible to cracking due to an increase in matric suction. As long as the swelling properties of bentonite remain intact, these cracks have the potential to heal upon rehydration and the GCL will regain its low hydraulic conductivity. To investigate this cracking process, a sample of GCL was slowly dried to known target moisture contents and the sample was interrogated non-invasively for cracks using digital x-ray imaging technology. This paper describes the image processing techniques developed to quantify cracks in GCLs and provides preliminary findings on the cracking patterns of an 'off the roll' liner.
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