?Robbins has signed a contract to refurbish and increase the diameter of a Main Beam TBM that is to excavate a 2.4km long adit for the Ceneri Base Tunnel, in Switzerland, from late 2008.

The contract was signed with customer Consorzio Monte Ceneri (CMC) JV, which consists of CSC, Lugano, Frutiger, Thun, Rothpletz, Lienhard + Cie, and Aarau. Financial terms of the contract were not disclosed.

Excavation of the adit, eastward from Sigirino, is scheduled to start in the third quarter of 2008 and take about two years.

The 9.7m diameter TBM is to be fitted with 19” cutters to bore through schist, molasses and orthogneiss with UCS ranging over 30MPa-130MPa to take the adit to the middle of the future north-south running main tunnels.

Robbins said that no squeezing ground or significant water inflows are anticipated. The company added that it was designing new probe drills for the TBM and added that temporary support in the drive would include rock bolts, ring beams and shotcrete. The spoil from the drive is to be stored for later use in concreting works.

The TBM is to be refurbished near Milan, which will involve increasing the diameter of the cutterhead from 7.6m. The TBM was previously used to bore part of the headrace tunnel on the Kárahnjúkar hydro scheme in Iceland (T&TI, July, p6).

From nearby in Sigirino the exploratory tunnel for the project was bored, ending in an excavated chamber adjacent to where the Robbins TBM is to terminate the access adit by 2010.

The Ceneri Base Tunnel between Camorino and Vezia, near Lugano, will be formed of twin 15.4km long rail tunnels and is to be operational by 2019. Tender documents for the main tunnels are under preparation by Swiss client AlpTransit, which is also responsible for building the 57km long Gotthard Base Tunnel.

In terms of excavation method, from the Sigirino access adit northwards the main running tunnels are to be driven by drill and blast; to the south, there are to be two sections of drill and blast plus a pair of 4km long stretches driven by TBM.


Installation caverns for the Ceneri TBMs