Architecture and management of a geological repository - Andra

7 – The shafts and the driftsFigure 7.7.4Experimental seal made up of bentonite blocks - Tunnel Sealing Experiment inCanada (these blocks would be larger at industrial scale).For reference, before the core is constructed, the drift equipment such as rails, pipes, cables and theroadway will be removed to prevent them creating a favoured path for water.7.7.2.3 Retaining plugsThe retaining plugs planned to contain the core mechanically must resist the initial swelling pressureapplied (3 MPa). They assist therefore in controlling the core resaturation phase: simple geometry forthe core and support face encourage homogeneity of resaturation and predictability of the swellingpressure.These plugs are designed in high-performance, non-reinforced concrete, choices dictated basically bydurability. High-performance concrete is more compact, water percolates through it less and itsalteration is delayed accordingly. The lack of reinforcement prevents fissuring from corrosionproducts expanding. It does however create a design constraint: these plugs must work by compressiononly. This may be achieved by a conical shape.The low permeability of the bases is thus a guarantee of robustness: it contributes to restricting thewater flow reaching the clay core in the event of abrupt hydraulic head and thus protects it from therisk of mechanical erosion.DOSSIER 2005 ARGILE -ARCHITECTURE AND MANAGEMENT OF A GEOLOGICAL DISPOSAL SYSTEM313/495