Largest TBM to bore in Italy

The largest TBM ever built will start boring next year in Italy. The 15.55m diameter, 120m long, Herrenknecht Earth Pressure Balance Shield will be used on the extension to the A1 motorway between Bologna and Florence.

The 4,300t machine with its 12,000kW cutterhead power will be used to bore the Sparvo Tunnel, consisting of two parallel-running 2.5km tubes, both of which will accommodate a three-lane road. The profile of the tunnel will set a new record in mechanised tunnelling as far as the drilling diameter is concerned.

Italian contracting company Toto Construzioni Generali will carry out the tunnelling works in loose soils with a presence of gas using EPB technology. The project was awarded to the Vianini Lavori/Toto Construzioni Generali/Profacta joint venture by the client Autostrada per l’Italia.

Construction of the tunnel is considered to be the most challenging part of the overall project, due to the size and geological conditions. The Italian contracting company Toto Construzioni Generali decided to use mechanised tunnelling technology to improve work safety and to accelerate the works.

Preparations for the assembly of the record-breaking TBM have already started in Schwanau. A tight time schedule has been set for the construction of the Sparvo Tunnel. In line with the current planning, the machine is expected to start tunnelling near Florence towards the north as early as the first half of 2011. The 6-7 lot is the last section of the Variante di Valico project, which will considerably reduce the travelling time between Bologna and Florence for up to 90,000 vehicles per day after the alternate route is opened according to schedule at the end of 2013.