Underground Research Laboratories play an important role in the development of radioactive waste repositories in deep geological formations, from both scientific and technological standpoints. In this context, the French national radioactive waste management agency (Andra) has developed the Meuse/Haute-Marne Underground Research Laboratory (MHM URL) at Bure, about 225 km East of Paris. The host formation consists of a Callovo-Oxfordian (COx) claystone found between 420 and 550 m depth, surrounded by poorly permeable carbonate formations. The excavation worksite in the COx claystone is a scientific experiment in itself to characterise damage induced by excavation and support. Drift intersections are always complex structures due to their difficult design and construction. A specific experiment has been performed in the URL to study the intersection between two perpendicular drifts. Geotechnical and geological measuring equipment/surveys have been set up to study the rock mass deformations, and to complete the characterisation of the excavation-induced fractures around this drift intersection. The extent of fractures potentially significant for radionuclide migration is known as the Excavation Damaged Zone (EDZ). A scientific study on EDZ characterisation has shown that the shape of the fracture network depends on the orientation of the drift in relation to the orientation of the in situ stress field. 3D modelling of the intersection of the GCR2 and GVA2 galleries was carried out using 2 constitutive models. Comparison of the computed plastic extensions for these two models provides better understanding of the complex geometry of excavation-induced fractures in intersection zones.
Mechanical Behaviour of Flexible Support Intersection Between Two Perpendicular Drifts Excavated in the Callovo-Oxfordian Claystone
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Djizanne, H., Armand, G., Renaud, V., and M. Souley. "Mechanical Behaviour of Flexible Support Intersection Between Two Perpendicular Drifts Excavated in the Callovo-Oxfordian Claystone." Paper presented at the ISRM International Symposium - EUROCK 2020, physical event not held, June 2020.
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