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Hydro-mechanical behaviour of the Cobourg limestone

Abstract of the article published in:
International Journal of Rock Mechanics and Mining Sciences

X. Su, T.S. Nguyen, Z. Li
Canadian Nuclear Safety Commission
M.H.B. Nasseri, R.P. Young


The hydro-mechanical behaviour of the Cobourg limestone was investigated with laboratory triaxial tests with axial loading parallel and perpendicular to the bedding planes. The experimental results show that the direction of loading with respect to the bedding orientation seems to influence the mechanical response of Cobourg limestone. However, the measured permeability of the intact Cobourg limestone does not show significant variation for different loading orientations. The permeability measured post failure is two to three orders of magnitude higher than that of the intact rock. This means that the permeability of the highly damaged limestone due to excavation could be at least three orders of magnitude higher than that of the undamaged rock. The variation of k as a function of rock damage is confirmed by the evolution of wave velocity measurements and supported by the thin section image of micro- and macro-cracks observed post-failure. This suggests that the excavation damaged zone could be a preferential pathway for radionuclide transport and must be considered in the design and safety assessment of deep geological repositories for the management of radioactive wastes.

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