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Injection tests and 3D lidar scans in the Tournemire underground laboratory

From October 21-24, 2024, employees of the GFZ sections “Seismic Hazards and Dynamic Risks”, “Geomechanics and Scientific Drilling” and “Geoenergy”, together with the operator of the Tournemire underground laboratory, IRSN, carried out injection tests separately in the core (fault core zone) and the loosening zone (fracture damage zone) of a fault zone in clay rocks (see Fig. 1). The acoustic events were recorded by a network of borehole sensors to enable subsequent localization of the rock zones through which the flow had passed. The 3D-US Lab simultaneously carried out 3D lidar scans throughout the underground laboratory (Fig. 2) to provide a high-resolution digital model of the cavities for evaluation. This involved the use of so-called reference spheres (see Fig. 3 and 4), which were placed as an attachment on the already geodetically measured receiver locations of the active seismics.

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Fig. 1: Performing the injection tests in Gallery 03 East
Fig. 2: 3D scan of the underground laboratory of Gallery 03 East using the GeoSLAM ZEB Horizon RT Mobile Scanner from FARO
Fig. 3: Reference spheres along Gallery 03 East for the 3D scans
Fig. 4: Intensity plot with reference spheres in red