Full text loading...
-
Geomechanical Characterization and Numerical Parametrization of Opalinus Clay with Application to Underground Structures
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, Fourth EAGE Shale Workshop, Apr 2014, Volume 2014, p.1 - 5
Abstract
Summary
Results of a new geomechanical testing program of Opalinus Clay core samples from a deep geothermal well in northeast Switzerland are presented. The experimental findings are in qualitative agreement with previously reported characteristics of the mechanical behaviour of Opalinus Clay. These characteristics comprise of a distinct strain softening irrespective of the degree of overconsolidation, anisotropy in elastic and strength properties, complex non-saturated and moderate swelling behaviour. Based on the relatively strong localization of deformation and pronounced brittleness, a bi-linear Mohr-Coulomb model with a tension cut-off was chosen to represent failure behaviour. Undrained triaxial deformation tests were then reproduced numerically using FLAC 3D software and a bilinear, strain softening ubiquitous joint constitutive model, capable of accounting for anisotropic strength but neither anisotropic nor stressdependent elastic properties. Comparison between laboratory and numerical results highlights that adequate reproduction of strength evolution can be achieved either parallel or perpendicular to the plane of anisotropy assuming isotropic elasticity, but not in both directions. Given this limitation the appropriate choice of modelling input parameters is discussed for application to cavern stability assessment for potential repositories in Opalinus Clay at a depth of 600m.
© EAGE Publications BV