Determination of deformability parameters on overcores in heterogeneous non linear anisotropic rocks

This paper presents the preliminary validation of a new stress calculation model for the triaxial CSIR cell that allows to include the heterogeneous non linear anisotropic stress-strain relationships found in most rocks. This interpretation methodology is an extension of a stress calculation model developed for the doorstopper measuring technique ( Corthésy et al., 1993a ). It is based on the modelling of rock behaviour using first and second order volumetric and shear stress-strain relationships. The hypotheses required for the passage from a 2D to a 3D model are presented. The validation of the methodology was done in the laboratory on hollow cylinders recovered from stress measurements performed at the URL near Pinawa, Manitoba, using the AECL modified CSIR triaxial cells. The stresses calculated with the proposed methodology are compared to those calculated with more conventional stress calculation models.