Progressive Excavation Disturbance Zone Evolution during and Post Mine-by Tunnelling (PRECODE)
Funding: Bundesgesellschaft für Endlagerung (BGE)
Project duration: 2021-2024
Project Partners: York University (Canada), Dalhousie University (Canada), ETH Zurich (Switzerland), BGE Tech (Germany)
Fracture initiation and propagation in the surrounding of tunnel excavations in highly stressed rocks may initiate during the tunneling process and develop over time. These progressive brittle fracturing may lead to an interconnected fracture network typically associated with the radiation of micro-seismic signals. Within the excavation damage zone (EDZ), the permeability is often enhanced by two to three orders of magnitude and – in the framework of nuclear waste disposal – may provide preferential pathways for radionuclide migration. Within the PRECODE experiment, we investigate the development and time dependent changes around a tunnel at the Bedretto Underground Laboratory for Geosciences and Geoenergies (BULGG) in Ticino (Switzerland). The infrastructure and experimental design will be integrated with ongoing projects at LIH, such as the FEAR and SPINE experiments. Within PRECODE we will establish a new, 100 m long experimental tunnel as a branch from the existing Bedretto tunnel, which will be densely instrumented with strain, pore pressure and micros-seismic sensors prior to the excavation.
In main objectives of the PRECODE experiment are to understand: (1) Short-term rock mass behavior and EDZ formation during tunnelling; (2) Long-term fracture propagation within the EDZ associated with environmental conditions; (3) Permeability changes with time around an open excavation and (4) the impact of tunneling on dislocations across nearby fault zones.
Funding Agency and Project Partners: