Induced fracturing in the Opalinus Clay: an integrated field experiment

The Opalinus Clay is under consideration as a potential host rock for a nuclear waste repository in Switzerland. The performance of the repository may be affected by an Excavation Disturbed Zone (EDZ), which is inevitably created when an underground opening is constructed. A test niche was sequentially excavated and monitored in the Mont Terri Rock Laboratory, Switzerland, to obtain a description of the induced fracturing in the EDZ during and after the excavation and to identify the mechanisms that dominate their formation. The field investigation provides essential data for an integrated development of an experimental EDZ model that describes the in situ geological conditions, induced fracturing pattern, and rock mass response. The approach used in the field investigation is presented along with preliminary results.