Architecture and management of a geological repository - Andra

6 – Overall underground architectureThe mechanical properties of the median part are weaker than those of other parts of the Callovo-Oxfordian formation. This ensures the study takes a conservative approach as regards the geotechnicalfeasibility of the repository.As the maximum dip of the layer is 3%, the direction of this dip is not a determining factor in theoverall architectural design.6.2.4.2 Repository component topologyThe topology taken into account favours the long-term hydraulic functioning of the repository. Therepository has a dead end type tree architecture from the cells to the shafts. On all levels of the treestructure, access to each element of the repository is via a small number of clustered access ways.At this stage in the studies, the incorporation of this architectural topology shows its feasibility despitethe inherent constraints from the point of view of ventilation in particular.6.2.4.3 Drift arrangementThe drifts and cells are arranged over a rectangular grid. Thus, all the drifts and cells to be sealed canbe oriented parallel to the main horizontal stress to limit damage to the argillite in the vicinity of theseals.6.2.5 Description of the B waste repository zoneFigure 6.2.2Layout of B repository zoneB packages whose physical and chemical properties differ are disposed in different modules (seeChapter 5). In Figure 6.2.2, packages containing no organic matter have been grouped together in subzone1.The space between the cells is defined by geotechnical dimensioning. The centre-to-centre distancebetween the cells used here is 72 meters which leaves a pillar of at least 5 times the diameter of thecells between two cells whose excavated diameter is 12 meters in order to ensure good stability.DOSSIER 2005 ARGILE -ARCHITECTURE AND MANAGEMENT OF A GEOLOGICAL DISPOSAL SYSTEM261/495