TERNA, the Electric Power Transmission Company, has awarded SELI the contract for the construction of the underground works for a new cable line that will transport clean energy from Sicily to Calabria on the Italian mainland. The contract, worth US$54.8M, with US$24.5M for TBM works alone, includes excavation of a 2,842m tunnel using a 4.09m diameter Double Shield TBM, and a 353m deep vertical shaft. The tunnel will bring two sets of cables from Sicily’s Favazzina harbor to the Scilla power station on the mainland, some 630m above sea level.
The TBM cutterhead will have 27 x 17” tools. Tools 1 to 14 are frontal while 15 to 26 are peripheral. The twenty-seventh tool allows extra excavation of a 5cm diameter radius beyond the 4.09m diameter. The cutterhead will be powered by 5 x 200kW electric motors with a total output of 1,000kW. Optimum speed of the bi-directional cutterhead will be between 10 and 11 rpm, with a maximum speed of 14rpm.
The TBM system will allow for grippers with a maximum force of 2,155kN, and a total of 4,310kN for the two hydraulic cylinders.
Muck evacuation will be via a 500mm wide conveyor at speeds of 2.5 m/s and a maximum capacity of 250t/h.
Excavation is scheduled to begin in May, 2012 and to be completed in March 2014.