Self-Sealing of Localised Cracks in Boom and Opalinus Clay Hollow Cylinders

The SELFRAC project aimed to study the fractures within the Excavation Damaged Zone (EDZ) around galleries in the Boom clay and Opalinus clay formations and their possible sealing/healing with time. Tests carried out at LMR-EPFL aimed at quantifying on the same sample the increase in permeability induced by a localised crack, and subsequently the potential self-sealing process of this localised crack. The tests were performed in triaxial cells on hollow cylindrical samples and consisted in radial permeability measurements before and after the tensile fracturing of the clayey samples. In both clays, sealing processes are observed. However, the reduction in hydraulic conductivity after fracturing is much slower in Opalinus clay than the one in Boom clay (extremely fast recovering of the virgin clay permeability).