Characterisation of induced discontinuities in the Boom Clay around the underground excavations (URF, Mol, Belgium)

Excavation works were carried out in Boom Clay to extend the underground research facility in Mol (Belgium) located at a depth of 223 m below the surface. The attempt to characterise the extent of the Excavation Damaged Zone, or EDZ, around the second shaft, using seismic measurements and cored borings, was successful, as proven by observations during further excavation works in the investigated area. No evidence for the occurrence of natural discontinuities was found. Using an industrial technique, an 84-m-long gallery was excavated in the Boom Clay. These excavation works induced a symmetrical pattern of discontinuities and clearly limited the EDZ extent.