SELI has broken through on the first of Rome Metro B1 Line’s 2.68km long twin-tubes at Piazza Bologna Station. Seli is acting as subcontractor to the JV Salini Costruttori – Tecnimont, and is constructing the twin tubes using two 6.78m diameter EPB DSU TBM. The second machine is due to breakthrough on the parallel tube in mid November.
The contract for the new Metro B1 line was awarded by the client, Roma Metropolitane to the JV, which awarded SELI the subcontract to excavate and line the two 2.68km long twin-tubes with 350mm-thick precast concrete segments in a 6+1 configuration.
The two 6.78m-diameter TBMs have been driving the tunnels from two opposite portals. The tunnelling system was engineered and designed by SELI, which also took charge of the manufacturing the auxiliary equipment including the back-up and rolling stock. The TBMs were manufactured by Herrenknecht, and the tunnel conveyor by Continental.
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The two machines advanced at depths of 30m and maintained an impressive average daily output of 16.8m/d (12 rings/d) while working at 3-5 bars of EPB pressure.
The geology along the alignment was made up of loose clay and silt soil and pressuring groundwater. At times excavation proved challenging due to the complex hydrogeology of the ground, and a host of sensitive buildings above the route. The new metro line runs beneath one of the most urbanised areas of the Italian capital, with numerous historical buildings and archaeological finds in abundance.
The tunnelling crews successfully prevented surface settlements and structural damage to the historical buildings, whilst also crossing the Aniene River.
Excavation was completed as scheduled, in approximately 2.5 years.
In the coming months, SELI will also complete excavation of the new extension line between Conca D’Oro and Jonio stations using a third 9.75m diameter TBM.