The boom clay formation has been selected as a potential host rock formation for the geological disposal of radioactive waste in Belgium. The aim of the Clipex project was to further characterise the hydro-mechanical behaviour of this formation and the excavation-disturbed zone, during the excavation phase of the extension of the HADES underground research facility at Mol (Belgium). Comprehensive instrumentation was installed in situ in order to monitor the hydro-mechanical parameters ahead of the excavation front, which was realised with a tunnel-boring machine. This enabled comparison of the in situ measurements with the blind prediction exercise performed earlier. The results demonstrate that it is possible to construct galleries by an industrial technique at great depth in boom clay keeping the disturbance of the host-rock at an acceptable level for the long-term safety of the repository. The instantaneous hydro-mechanical response around a gallery during its excavation was fully characterised with a high level of confidence concerning the results. The numerical simulations gave reliable blind predictions in terms of displacement and pressure on the lining allowing an optimum design of the tunnel machine. One important finding of the project is the unpredicted observation of hydraulic perturbation deep inside the formation. Future model developments are therefore necessary to explain the variation of pore water pressure in the far-field considering a fracturing process and the delayed effects through the viscosity of the clay skeleton. The Clipex project is a great success and constitutes an important step in the development and design of an underground nuclear waste repository.
|Publisher||Publications Office of the European Commission|
|Number of pages||150|
|State||Published - 2003|