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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).

To explore connections between rock strength and rock falls, we undertook a comprehensive rock mechanics testing program for six granitic rock types in Yosemite Valley (California, USA) where rock falls are a common geomorphic and sometimes hazardous process. We collected samples from boulders located at the base of cliffs, with the inherent assumption that the intact boulders should provide reasonable estimates of full-strength values. Our testing program included unconfined compressive strength tests, triaxial compressive strength tests, Brazilian tensile strength tests, and Mode I fracture toughness strength testing using two different types of samples – chevron bend (CB) and cracked chevron notched Brazilian disk (CCNBD). Our results, consisting of 88 individual tests, provide the most detailed evaluation of rock strength in Yosemite Valley to date. These results provide the data needed to evaluate the various failure modes (e.g., shear failure of wedge instabilities, tensile failure of overhangs) that might be expected for rock falls from cliffs in Yosemite. We expect that these data will provide an important resource for the evaluation of rock falls and other geomorphological studies in Yosemite National Park.