Excavation of the adit for the Ceneri Base Tunnel by a 9.7m diameter Robbins TBM started last month at Sigirino, Switzerland.
The 2.4km long adit is being driven to reach the mid launch points for the later twin bore excavations for the main running tunnels, the contracts for which have yet to be awarded.
Geology along the adit alignment comprises schist, molasses and orthogneiss of UCS 30MPa-130MPa. Contractor Consorzio Monte Ceneri (CMC) JV was to have commenced excavation of the adit in the third quarter of this year but, along with construction of the installation caverns, the work is still to last two years.
The main beam TBM was previously used, as ‘TBM1’, to excavate a 14.65km stretch of the 39.6km long headrace tunnel on the Karahnjukar hydropower project in Iceland. It was refurbished near Milan, increased in diameter from 7.6m and fitted with 19” cutters. Robbins designed new probe drills for the machine and said previously that no squeezing ground or significant inflows were expected (T&TI, September 2007).
The adit bore will terminate where it meets an existing exploratory tunnel. At the junction the installation caverns have been built, from where the main running tunnels will be driven and which will house concrete batching plant.
CMC JV consists of CSC, Lugano, Frutiger, Thun, Rothpletz, Lienhard+Cie, and Aarau.
The 15.4km long, twin main running tunnels are to be driven by drill and blast and TBM. The north end tunnels will be excavated as twin 8km long drill and blast drives, and the method will also be used for a pair of 1.8km long bores in the south section. The remaining, parallel 4km long tunnels in the south sections will be driven by TBM.
Client AlpTransit expects the Ceneri rail route to be operational by 2019. AlpTransit is also building the Gotthard Base Tunnel (T&TI, February).
Robbins TBM ready to excavate adit for the Ceneri Base Tunnel, in Switzerland
