Architecture and management of a geological repository - Andra

5 – Repository Modules5.1.5 Construction of the B cellsThe construction process can be sub-divided into three basic processes:- excavation,- installation of the ground support to ensure that the site is safe,- installation of the lining ensuring the stability of the structure throughout the operation andmonitoring periods.Underground work has been carried out for each of these processes. At this stage in the studies, onlythe use of standard equipment has been taken into account and proven operating methods have beenfavoured.5.1.5.1 Excavation methodSeveral options can be envisaged for excavation of the cell: borehole drilling and blasting, roadheaderand full-face tunnelling machine.At this point in the studies, the roadheader machine (Figure 5.1.22) is the preferred option forexcavating the access drift and the cell. This technique is well suited to the characteristics of theargilite and the geometry of the cell. By comparison, the full-face tunnelling machine is cumbersomeand less suited to the configuration of the cell owing to its reduced length (about 250 m) and thedimensional restriction imposed by the cell entrance chamber. Given the mechanical properties of therock and the diameter of the cell, it may be necessary to excavate the cell in two passes, whereas theentrance drift could be excavated in a single pass. The development of a specific roadheader wouldmean the section of the cell could be excavated in a single pass.5.1.5.2 Installation of the support and lining• The cellInstallation of the ground support in the cell, consisting of short rock bolts, a welded mesh andshotcrete, as described in the previous sections, is done with a bolting jumbo (Figure 5.1.22) and anelevator platform. The shotcrete is installed with a projection jumbo.The choice of method for installing the lining is linked to the support method. It may consist ofconcrete poured in-situ or of prefabricated concrete segments. For a bolted support (or one usingarches), the first option should be preferred. It should be noted that if segments are used, the supportfunction will be provided by a shield integral with the excavation machine.Figure 5.1.22Examples of roadheader and bolting jumboDOSSIER 2005 ARGILE -ARCHITECTURE AND MANAGEMENT OF A GEOLOGICAL DISPOSAL SYSTEM184/495