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Fig. 12 | Swiss Journal of Geosciences

Fig. 12

From: Analysis of tectonic structures and excavation induced fractures in the Opalinus Clay, Mont Terri underground rock laboratory (Switzerland)

Fig. 12

a Schematic borehole mouth configuration at the tunnel wall in Gallery 98, gallery metre GM 84.5. The length of each of the 16 boreholes is around 1 m. The numbers between two boreholes indicate the distance between the corresponding test intervals in cm. b Log-plot of calculated transmissivity (m2/s) versus time, derived after each of the nine hydraulic tests. The negative trend shows that the transmissivity in the EDZ fracture network decreases by about two orders of magnitude over a period of 2 years. This reduction in transmissivity is due to swelling processes with subsequent reduction of the fracture widths, which is termed self-sealing of EDZ fractures

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