Piazzale Bologna Stretch of Rome B1 metro completed The contract for the new metro B1 line was awarded to the JV Salini Costruttori - Tecnimont by the client, Roma Metropolitane. The JV awarded SELI the subcontract excavation and lining of twin 2.684 km-long tunnels with 35 cm-thick precast concrete segments in a 6+1 configuration.On 20.09.2010 the TBM S-387 completed excavation of the first tunnel by breaking through the diaphragm at Piazza Bologna station. The second of the twin tunnels should be completed by mid-November, 2010. Two 6.78 m-diameter EPB DSU TBMs driving from two opposite portals are being used on the project.The tunnelling system was engineered and designed by SELI, who were also in charge of manufacturing auxiliary equipment, including the backup and rolling stock. The TBMs were manufactured to SELI specifications by Herrenknecht and the tunnel conveyor by Continental.The tunnels are 30 m below surface, where the TBMs maintained an impressive average output of 16.8 m/d (12 rings/d) while working at 3-5 bars of EPB pressure. Excavation proved challenging due to complex hydrogeology along the alignment and proximity of surface buildings. During next month, SELI will also complete excavation of the new extension line between Conca D'Oro and Jonio stations using a third 9.75 m-diameter TBM.For background and history of this project, click here, here and visit tunnelbuilder archive it/31. Visit www.romametropolitane.it. 39/10. Arrival of TBM in Piazzale Bologna station