Hydromechanical modelling of tunnel excavation in claystone

Country / Region: independent

Begin of project: January 1, 2009

End of project: December 31, 2023

Status of project: February 24, 2023

German Version

Fig.: Hydraulic and mechanical instrumentation around the MB-A tunnel, Mont Terri Rock Laboratory, Switzerland Source: BGR

As a result of tunnel excavation in claystone, the hydromechanical conditions change in the influenced area . To record such changes, so-called mine-by-experiments are carried out. Different measuring sensors are placed at different locations around the tunnel before excavation, and the mechanical and hydraulic changes in the rock will be recorded during the excavation procedure. To interpret the in-situ measurements, numerical simulation will be used.

The BGR has developed a model to describe the coupled hydromechanical processes in the claystone, taking into account an unsaturated state, that was validated using the measurement data from the mine-by-experiments in Tournemire (F). The further development of the OGS code in cooperation with Helmholtz Centre for Environmental Research (UFZ) Leipzig, with the extended functions (e.g., anisotropic plasticity), enables a realistic analysis, with increasing accuracy, of hydromechanically coupled processes in rock. Based on the knowledge and experience gained, the model and the extended program system are now being applied in the context of numerical calculations for tunnel excavations in the underground laboratories at Mont Terri (CH) and Bure (F). A current application is the modelling of the MB-A experiment conducted during the laboratory extension at Mont Terri in 2019. The objectives of these calculations are the interpretation of the measured mechanical and hydraulic changes (pore water pressure, deformation) in the rock mass, and the verification of the developed model.

Partner:

NAGRA: Nationale Genossenschaft für die Lagerung radioaktiver Abfälle (CH)

ANDRA: French national radioactive waste management agency