Deformation behavior of clay cap barriers of hazardous waste containment systems: Full-scale and centrifuge tests

Abstract : The objective of this paper is to study the deformation behavior of a clay cap barrier of waste containment system for storing hazardous waste. The risk of bending of a clay barrier in case of differential settlements within underlying waste is focused in the present study. Field bending “bursting tests” were performed in France on clay barriers of 0.7 m thickness at different water contents. An attempt has been made to determine limiting distortion level at which cracks are initiated. The cap clay barrier configuration tested through field bursting tests was simulated at 12.5 g in a geo-centrifuge on model cap clay barriers of 56 mm thickness subjected to bursting mode of failure. Digital image analysis technique was used to ascertain initiation and propagation of cracking at the onset of differential settlements. Further influence of discrete and randomly distributed polypropylene tape fibers in restraining cracking tendency of the clay barrier was evaluated through a centrifuge model test. With an increase in the molding water content and the presence of randomly distributed fibers, an increase in limiting distortion level was observed. Use of 0.5% of fiber dosage and 90 mm long discrete fibers was found to restrain propagation of cracking of a clay barrier subjected to differential movements. Analysis and interpretation of field bursting tests was found to be in good agreement with physically observed centrifuge model test results.