Tome Architecture and management of a geological repository - Andra

5 – B waste repository zone• Cutting out the sealing zoneThe section of the entrance drift right above the seal construction zone is over-reamed to cut out andextract the volume of rock damaged by the excavation works. Cutting out the granite may be carriedout using ornamental masonry work methods adapted to the underground situation (diamond-tippeddisk sawing and jack rock-splitting or boreholes and diamond-tipped cable sawing (Figure 5.6.11,[15]).Close-up of diamond-tipped cableCutting machineFigure 5.6.11Cutting ornamental granites with a diamond-tipped cable• Backfilling the cell headThe volume that corresponds to the cell head and the portion of the access drift upstream of the seal isbackfilled (cementitious backfill). The backfill is supported by a permanent masonry form constructedin front of the radiological protection.• Construction of the cell sealThe cell seal is made up of a swelling clay core confined by two concrete abutments. Cell sealconstruction is similar to that of a drift seal (cf. § 4.2.2.6). The clay core is about fifteen metres long.5.6.5.2 Closure of a disposal moduleThe closure of a disposal module comprises the following staged sequence:- the connecting drifts and access drifts downstream of the cell seals are entirely backfilled. It isplanned to use low permeability backfill made up of granite aggregates and swelling clay, and tocompact it mechanically into place (cf. § 4.2.2.6);- dismantling all the module operating installations (ventilation, drainage and energy);- constructing module seals in the connecting drifts downstream of the faults that delimit the hostblocks (cf. § 4.2.2.6).Dossier 2005 Granite - ARCHITECTURE AND MANAGEMENT OF A GEOLOGICAL REPOSITORY152/228