AMP - BLG-5 : Mont Terri Rock Laboratory - Geophysical investigation of the Excavation Damaged Zone during a mine-by experiment
This report presents the results of a multidisciplinary mine-by experiment conducted in the Mont Terri Rock Laboratory to investigate the Excavation Damaged Zone (EDZ) in Opalinus Clay.
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Abstract
This report presents the results of a multidisciplinary mine-by experiment conducted in the Mont Terri Rock Laboratory to investigate the Excavation Damaged Zone (EDZ) in Opalinus Clay. The study aimed to understand the spatial and temporal evolution of excavation-induced damage using geophysical methods including seismic surveys, geo-electrical measurements, noble gas profiling, and self-potential monitoring. The experiment involved the excavation of an 8-meter segment (EZ-G08) between two galleries, instrumented with 37 boreholes.
Results reveal strong anisotropy in elastic properties, fracture network evolution, dynamic gas diffusion, and evidence of micro-seismicity linked to excavation stress changes. The EDZ was found to affect hydraulic and transport properties significantly, with variations in response depending on lithological facies. The findings contribute to safety assessments of deep geological repositories and enhance understanding of claystone behavior under excavation-induced stress.