Drained triaxial testing of shales: insight from the Opalinus Clay

The investigation of the mechanical behaviour swelling claystones and shales is challenging because their very low permeability high sensitivity to changes in water content. former makes it difficult carry out triaxial tests with controlled homogeneous pore pressure fields, latter results some possible effects when unsaturated extracted specimens are re-saturated prior being tested. This work presents data from drained performed on Opalinus Clay, designated as host rock for radioactive waste disposal Switzerland, at shallow depth close city Lausen. compared those recently published undrained same place, also two sets recent independently obtained Clay sourced greater Mt Terri Underground Research Laboratory. By comparing our Lausen specific which has been prevented, quite a good comparability shear strength observed confining effective stresses larger than 5–6 MPa. related small magnitude occurring above this stress during specimen hydration tests. question linearity criterion discussed respect both other ones. It suggested that be carried investigate whether perturbations due occur area could result nonlinear shape criterion. change Young modulus Poisson coefficient discussed, Callovo–Oxfordian claystone France, evidencing interesting similarities terms properties Young’s moduli.