Rome B1 b’thru, extension for Seli

Seli has holed through with the first TBM at Gondar station on the B1 metro line in Rome, and the subcontractor has secured an additional job to help extend the route still further, north to Jonio.

Two TBMs have been outside the box structure’s bulkhead for a few months as the delayed station was readied, and last month the first EPBM broke through and it is to be followed this month by the second.

The 6.77m diameter Herrenknecht shields (S-387, S-388) were launched at Conca D’Oro station in the middle of 2008 and reached the edge of Gondar station in the third quarter of last year.

Geology along the alignments was poor, comprising compressible clays and silty sands. EPB pressures were up to 3-4bar, and ground water head approx. 2.5 bar on the drives which also pass below the river Aniene. The tunnels are lined with (6+1) rings of 350mm thick Universal segments.

Seli is driving approx. 3km twin tubes to terminate at Bologna station by October. There is another intermediate station – Annibaliano – on the way. At Bologna, Line B1 will interchange with Line B.

The main contractor on the project is a JV of Salini Costruttori and Maire Engineering.

Separately on line B1, Seli has been awarded a subcontract by the JV of Salini and Tecnimont, to build the twin tubes in the opposite direction, north from Conca D’Oro to Jonio station.

Work involves excavation of a 950m long tube and a 150m long crossing of Jonio station. Similar geology is anticipated along the route to the other current stretch of B1 under construction, and the groundwater level is approx 17m above the tunnel crown.

The section is to be bored by a 9.79m diameter Herrenknecht EPBM, which is due to be launched in the second quarter. The 8.65m i.d. lining will consist of (7+1) rings with 400mm thick segments.