Temperature and Damage Impact on the Permeability of Opalinus Clay

The effects of temperature on the water transport properties of intact and damaged Opalinus (OPA) clay are investigated by using a recently developed hollow cylinder triaxial cell [Monfared (Int J Rock Mech Min Sci 48:637-649, 2011b)] that allows full saturation and drainage conditions in low-permeability clays and shales. The volumetric response of saturated OPA clay sample during a drained heating test shows an irreversible contraction after a temperature threshold. The permeability tests which are performed before and after the heating test show that the induced irreversible sample contraction by thermal loading reduces the permeability of OPA clay sample. In order to study the effect of temperature on the permeability of a damaged sample of OPA clay, the permeability tests are performed on a saturated sample previously sheared by a standard drained triaxial loading. The test results show no significant effect of shear-type damage on the permeability of the sample at 25 A degrees C and 80 A degrees C. The experimental results presented in this paper show the crucial role of the thermally induced strains on sample permeability. Thermo-elastic dilation leads to a slight increase of the permeability, whereas thermoplastic contraction leads to a reduction.