Subsurface structures

Structures at the experiment sites

Large span caverns are required at the experiment points PA and PG to accommodate the detectors. The dimensions for these underground volumes are shown in the table below. They will be constructed at different depths, depending on the absolute altitude of the tunnel alignment, its inclination and the topography at the locations. The tunnel and caverns will be located at a depth that is sufficiently distant from water bearing layers and as far as possible in stable ground conditions. Indicative values are presented in the tables below. Definitive depths indications will be known after the tunnel alignment can be optimised based on the subsurface geological and geotechnical investigation results are available. The construction sequence will be developed during the detailed design stage, after a decision to construct is taken. It will include benched excavations using rockbreakers and roadheaders with the primary support being provided by rock bolts, cable bolts and layers of steel fibre concrete. During the widening of the crown area of the experiment cavern, additional girder lattices and layers of steel fibre reinforced shotcrete will be installed. The lattice girders for the various excavation steps can be bolted together to ensure continuous rock support along the excavated area. The final lining will be in-situ cast concrete.

Each experiment site will also feature a service cavern at machine tunnel level near the experiment caverns with dimensions as indicated in the tables below. These caverns will be constructed in a similar manner to those for the experiments. At the experiment points, the spacing between the two caverns is between 60 m and 90 m (measured from the centre of the experiment cavern to the centre of the service cavern) as this allows the structures to be independent, to minimise the structural support needs and to reduce the risk and complexity during construction. Depending on soil and rock conditions the distance between experiment cavern and service cavern may be shortened slightly. The design depends eventually on the results of the subsurface investigations and the detailed technical designs to be carried out at a later stage.

PA (Experiment, Ferney-Voltaire)

PG (Experiment, Charvonnex)

Drawings and images

The following drawings and images aim giving an impression of the foreseen underground structures. These are generic conceptual drawings that do not represent designs. Specific designs for caverns and shafts will be developed during a specific design phase in which the equipment to be placed in the structures and its dimensions are known to a greater detail.

Structures at the technical sites

Each technical site will feature a service cavern at machine level with dimensions as indicated in the tables below near the experiment caverns. These caverns will be constructed in a similar manner to those for the experiments. The spacing between the tunnel and the cavern is about 50 m (measured from the centre of the accelerator tunnel to the centre of the cavern) to allow the structures to be independent, to minimise the structural support needs and to reduce the risk and complexity during construction. Depending on soil and rock conditions the distance between tunnel and service cavern may be shortened slightly. Such analysis is depends on the results of the subsurface investigations and the detailed technical designs to be carried out at a later stage.

PB, PD, PF, PH, PJ, PL (Technical)

Drawings and images

The following drawings and images aim giving an impression of the foreseen underground structures. These are generic conceptual drawings that do not represent designs. Specific designs for caverns and shafts will be developed during a specific design phase in which the equipment to be placed in the structures and its dimensions are known to a greater detail.