Faults and fractures in the Gallery 04 of the Mont Terri rock laboratory: Characterization, simulation and application

This paper deals with the reconstruction of a fracture network observed in an underground gallery of a tunnel buried in clay stones in Switzerland, below Mont Terri. The trace maps of the Gallery 04 and of the EZ-G niche of this site have first been digitized and used in various ways to characterize the data. The traces have been divided into two groups, i.e., the pre-existing faults in the gallery and the fractures of the excavated damaged zone (EDZ) in the niche. Each group has been analyzed individually. The number of data for the faults has turned out to be statistically significant, while it was very limited for the EDZ fractures. For both cases, the major statistical characteristics of the traces have been extracted and a reconstruction procedure developed and tested. A full example has been worked out; a gallery immersed in a reconstructed fractured porous medium has been meshed, and the electrical field created by a dipole at the wall calculated by solving the three dimensional Laplace equations in the fractures and in the porous medium.

Research Highlights
► Fracture trace maps on gallery walls at the Mont Terri Rock Laboratory are digitized.
► The major statistical characteristics of the pre-existing faulting are determined.
► The fracturation in the Excavation Damaged Zone (EDZ) is characterized.
► A reconstruction procedure including faults and EDZ fracturation is developed.
► A full example is worked out and an electrical monitoring experiment is simulated.