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STROEFUN: Improving the Contact Zone of Geotechnical Barriers

BGE TEC develops a method to test the permeability of the contact zone along the entire contour of a sealing cross section

To guarantee the safe containment of radioactive waste in a containment providing rock zone (CRZ), drift seals – in addition to the geologic barrier – play a fundamental role as they are to seal the access routes into the emplacement areas. Drift seals consist of a seal/abutment body made of magnesia- based concrete, the excavation damaged zone (EDZ) close to the drift contour, and the contact zone between the seal’s body and the drift contour. Regarding the functionality of the drift seal, these three components act in parallel. Thus, the component with the lowest hydraulic resistance is decisive for the drift seal´s effectiveness.

The functionality of the sealing body can be demonstrated by testing. The contact zone is influenced by constraint stresses that arise from the thermomechanical impact during concreting as well as from the different stress-strain relations of the rock salt and the sealing body. If the rock salt and the sealing body undergo equal deformation in the contact zone, constraint stresses arise and may lead to micro-cracks. Consequently, the permeability increases, which can be detected by permeability measurements. Typically, pointwise measuring results are available from permeability tests in boreholes. Within the joint R&D project STROEFUN, a method to test the permeability of the contact zone along the entire contour of a sealing cross section has been developed. Furthermore, the hydraulic conductivity of the contact zone will be reduced by injection measures. To test this method, a pilot test will be carried out in