MODELLING APPROACHES OF THE EXCAVATION DAMAGED ZONE (EDZ) AROUND THE OLD TUNNEL AT THE ARGILLACEOUS TOURNEMIRE SITE

摘要

Since 1988, the French Institute of Radioprotection and Nuclear Safety (IRSN) has studied fluid transport processes, confining properties and EDZ effects in argillaceous media at the selected site of Tournemire. In the framework of the DECOVALEX-THMC international project, Task C, related to the Tournemire site, was proposed by IRSN in order to evaluate and improve the capability of the codes to model the EDZ. This paper provides details of the work already performed in this task by the IRSN-CEA-EMP research team. The studies have concentrated on predicting the EDZ of the one-hundred years old tunnel. In order to evaluate the extent of this EDZ, both instantaneous and time-dependent rock mass responses to excavation are considered. To study instantaneous behaviour, elastic calculations followed by post-processing according to a Mohr-Coulomb anisotropic failure criterion were performed. After that, nonlinear damage calculations were tried in order to improve the previous calculations. To investigate the possible EDZ development over time, creep behaviour of argillite was taken into account and a hydro-mechanical analysis was performed in saturated conditions. In all the calculations, a vertical cross-section of the tunnel under plane strain conditions was considered. None of the linear or non-linear models used in this study correctly predicts the form or extent of the EDZ as observed around the tunnel at the Tournemire site.