Speaker
Description
Europe hosts thousands of decommissioned mines situated below inhabited zones with significant real estate prices. These inhabited sites, with histories of gallery collapse, are unsuitable for traditional active geophysical monitoring methods. A passive observation method with metre-scale precision is therefore required to support stakeholders' risk mitigation strategies. Muon absorption tomography is capable of passively imaging an endangered region at metre-scale precision, with no increased risk to site stability. Muodim and IRIS Instruments deployed two differing muon detector technologies with binocular vision, in a disused mine gallery, to image an unstable zone of characteristic size 50x50x30m. From 40+ days of data, both 2D results from each detector and combined 3D results show similar density distributions with mean rock densities of ~2.65g/cm3, coherent with geological observations. Crucially, 2D and 3D muography results also reveal strong evidence for a low density anomaly (-0.6g/cm3, ~7x7x9m in size) located between the surface and the closed gallery extremity. Evidence for a decompressed zone is consistent with the location of historical gallery roof collapse. To our knowledge, this is the first study to successfully combine both MicroMegas and Scintillator detectors in a 3D muography reconstruction. Muography results critically informed client decision-making to ensure safety of the area, protecting people and property. Such insights cannot be obtained using other existing technologies without endangering operators.