Architecture and management of a geological repository - Andra

5 – Repository Modules• The access driftFor the access drift, we have opted for a ground support using arches and shotcrete, with a subsequentlining with poured concrete. This technique avoids having to use rock bolts and thus preserves theground opposite the sealing zone as much as possible.5.1.5.3 Construction sequenceThis description mainly concerns the construction of the actual cell proper. It gives a possiblesequence of the operations to be carried out.Construction can thus be broken down into several phases; each phase consists of a series of workingcycles carried out over the entire length of the cell, before moving onto the next phase.• 1 st phase: excavation and support of the upper part of the driftDuring the first phase, illustrated in Figure 5.1.23, the work is organised into excavation - supportcycles. Each cycle corresponds to an advance of about 1.50 m depending on the rock supportrequirements. The roadheader excavates to a depth of 1.50 m (see top of figure) and immediatelyafterwards, a row of anchor bolts is installed. If necessary, horizontal bolts made from glass fibre areput in place to ensure the stability of the face.The shotcrete (bottom of the figure) is installed about ten metres behind the cutting face, in passes ofabout 3 m. If necessary, a thin layer of concrete can be sprayed right up to the face.• 2 nd phase: excavation and support of the lower part of the driftOnce the upper part of the cell has been excavated and its entire length supported, the next phase is toexcavate and support the lower part of the cell. This phase, illustrated in Figure 5.1.23 is comparableto the first phase.• 3 rd and 4 th phases: pouring the concrete slab and then the cell and abutmentsOnce the cell has been excavated and supported over its entire length, we move onto the finalconcreting phase, first of all the slab, then the vault and the sidewalls.The slab is poured in sections about 12 m long. The sections can be separated by dry seals to reduceconcrete cracking.Once the slab has been poured over the entire length of the cell, the vault and the sidewalls are poured.To do this, we use a mobile formwork (Figure 5.1.24) with the dimensions of the disposal chamber.Pouring is in sections of about 6 m. As with the slab, these sections can be separated by a dry joint.• 5 th phase: equipping the cellAfter finishing lining of the cell, it then has to be equipped: construction of a perforated wall at the endof the cell to regulate the airflow, installation of the finishing slab with handling grooves and rails,construction of the access chamber and installation of mechanical elements (door and handlingequipment).DOSSIER 2005 ARGILE -ARCHITECTURE AND MANAGEMENT OF A GEOLOGICAL DISPOSAL SYSTEM185/495