|CERN AC Note (2000-03)-General description of the CNGS Project|
|3. Underground structures|
|All civil engineering work for the CNGS project is underground. 1000 m of the tunnels and the access shaft are to be built in France, with the remainder in Switzerland (see Figure 10 on page 20 and Figure 11 on page 21):|
|Table 2: Underground structures|
|3.1 The temporary access shaft
This shaft is needed so that the civil engineering work does not interfere with works for the LHC. The shaft will have a diameter of 8 m and a depth of 57 m, and will be situated 130 m from the existing cavern ECA 4. It will be used only during the construction period. The excavation will be protected by shotcrete. Once the project is completed, the shaft will be covered by a concrete slab, and then topsoil so that the surroundings revert to their initial state.
3.2 The access tunnel
This tunnel will connect the existing cavern ECA4 to the target chamber. It will allow equipment and personnel access from Point BA4 of the SPS accelerator. Its length will be 769 m with an internal diameter of 3.10 m. The walls and ceiling will be shotcreted. The general slope of the structure will be 2.2%.
3.3 The proton beam tunnel
This tunnel will link the existing cavern TJ8 to the target chamber. It will be 590 m long and it will have an internal diameter of 3.10 m. The walls and ceiling will be of concrete poured "in-situ". The general slope will be 3.5%.