Retour sur l'analyse de la stabilité d'une galerie construite dans une argile faiblement induré à 225 m de profondeur dans le laboratoire souterrain HADES à Mol, Belgique: Feedback on the stability analysis of a gallery built in a poorly indurated clay at 225 m in the HADES Underground Research Laboratory in Mol, Belgium.

The feasibility of constructing tunnels in deep clay formation is an important step in the demonstration programme for the radioactive waste geological disposal. As part of this programme, the Connecting gallery, an 83 m long gallery, was successfully built in 2002 with industrial technique in the underground research laboratory (URL) HADES at a depth of 225 m in Mol. This gallery was instrumented with multiple instruments such as embedded strain gauges and prisms to monitor the variation in diameter. This monitoring set-up allows us to monitor its deformation and its behaviour in contact with the clay. The mechanical evolution determined with the embedded strain gauges gives important information on the stability of this structure, as the stability of the gallery has to be ensured to guarantee the continuity of the performed research. In addition, it brings valuable information concerning its interaction with the clay host formation that can be used to improve the future design of repository galleries. This work presents and analyses the measurements that have been done for almost 20 years at HADES, the strain evolution, the deformation mode of the lining obtained by the geodetic survey and, the stresses calculated from the strain gauges