Bentonite mechanical evolution – experimental work for the support of model development and validation

The objectives of the Beacon experimental studies are to provide input data and parameters for development and validation of models and to reduce uncertainties about conditions and phenomena influencing bentonite homogenisation. Both the homogenisation of an initially inhomogeneous bentonite system and the persistence or development of inhomogeneities in the bentonite system under various mechanical and hydraulic conditions are investigated. Eight experiment teams perform tests involving different bentonite materials and different hydraulic and mechanical boundary conditions. The experiments performed within Beacon address the hydro-mechanical behaviour of macroscopically homogeneous bentonite materials, (the influence of initial granulometry and of hydro-mechanical paths on the final properties of bentonite, constant load and constant volume tests on the Czech Cerny vrch bentonite), the issue of swelling into a limited void (experiments performed in constant volume cells partially filled with bentonite, at different scales and with different emphases), binary mixtures or artificial inhomogeneities (experiments using bentonite block/pellet or pellet/powder mixtures, and the influence of the degree of saturation on the shearing behaviour at a bentonite – steel interface. This report is the first Beacon WP4 deliverable on experimental work and presents the status at Beacon mid-term.