Convergence analysis of an unsupported micro-tunnel at the Meuse/Haute-Marne Underground Research Laboratory
L.-M. Guayacán-Carrillo, J. Sulem, D. M. Seyedi, S. Ghabezloo, A. Noiret, G. Armand, 2017. "Convergence analysis of an unsupported micro-tunnel at the Meuse/Haute-Marne Underground Research Laboratory", Radioactive Waste Confinement: Clays in Natural and Engineered Barriers, S. Norris, J. Bruno, M. van Geet, E. Verhoef
Download citation file:
Convergence measurements recorded for one representative micro-tunnel (diameter c. 0.7 m) in Callovo-Oxfordian claystone were analysed. The micro-tunnel was excavated in the direction of the horizontal principal major stress. In situ observations showed anisotropic convergence with the maximum and minimum values in the horizontal and vertical directions, respectively. The horizontal closure of walls was fitted on the basis of a semi-empirical convergence law. This law is a predictive model reflecting the global response of the ground to excavation works. As the convergence measurements were performed after the end of excavation, their evolution in time can only be related to the time-dependent behaviour of the ground and the effect of the face advance cannot be captured. It is shown that some parameters of the semi-empirical law did not change along the micro-tunnel. An easy and efficient method is thus proposed for the long-term prediction of wall closure by the fitting of a single parameter on recorded data. Comparison with a drift (diameter c. 5 m) highlighted the influence of the support installation and the rate of excavation on the variation in the parameter values of the semi-empirical law. The vertical closure of the micro-tunnel walls, which showed a very weak evolution over time, was analysed based on the rate of convergence.
Figures & Tables
It is internationally accepted that the safest and most sustainable option for managing radioactive waste is geological disposal, utilizing both engineering and geology to isolate the waste and contain the radioactivity.
This Special Publication contains 25 scientific studies presented at the 6th conference on ‘Clays in natural and engineered barriers for radioactive waste confinement’ held in Brussels, Belgium in 2015. The conference and this resulting volume cover many of the aspects of clay characterization and behaviour considered at various temporal and spatial scales relevant to the confinement of radionuclides in clay, from basic phenomenological process descriptions to the global understanding of performance and safety at repository and geological scales.
The papers in this volume consider research into argillaceous media under the following topic areas: large-scale geological characterization; general strategy for clay-based disposal systems; geomechanics; mass transfer; bentonite evolution and gas transfer.
The collection of different topics presented in this Special Publication demonstrates the diversity of geological repository research.