Determining Crack Aperture Distribution in Rocks Using the 14C‐PMMA Autoradiographic Method: Experiments and Simulations.

Because cracks control the global mechanical and transport properties of crystalline rocks, it is of a crucial importance to suitably determine their aperture distribution, which evolves through alteration processes and rock weathering. Due to the high variability of crack networks in rocks, a multiscale approach is needed. The 14C‐PMMA (polymethylmethacrylate) method was developed to determine crack apertures using a set of artificial crack samples with different controlled apertures and tilt angles and also using Monte Carlo simulations. The experiments and simulations show the same result: the estimation of apparent aperture wA was successful regardless of tilt angle, even if the estimates are less accurate for low tilt angles (<30°). The uncertainties on the estimation of the real crack aperture wR arise from the unknown tilt angle. The ability of the 14C‐PMMA autoradiography method to estimate crack aperture distributions in rock samples was successfully confirmed on a sample of Grimsel granodiorite. Key Points: A new method for determining multiscale crack apertures in rocks is proposedThe method is based on impregnation of connected porosity with a radioactive resin: 14C‐PMMA (Plexiglas)Crack apertures are obtained from the analysis of the resulting autoradiography [ABSTRACT FROM AUTHOR]