The JV Coestra/Bonciani/ACMAR of Florence was awarded the contract for the 1.8 km-long Line 1 metro extension from Sesto FS to Monza, in Italy. The contract, value EUR61.04 million excluding VAT, includes four 8.90 m internal diameter, 84 sq m twin tunnels and two new stations at Sesto Restellone and Cinisello-Monza. Read the detailed report. 10/13.

On November 12th 2012 works started at GN2 portal (jet-grouting), from Cinisello-Monza station. In mid-February 2013 the progress was 50 m.

On January 17th 2013 works started at GN3 portal (jet-grouting), from Cinisello-Monza station. In mid-February 2013 the progress was 20 m.

 Other underground works:

• Access adit ring (km 13+442.763): used as Fire Brigade access and escape exit, open cut, reinforced concrete 100 cm-thick diaphragm walls, outer dimensions 7.60 x 14.00 m, height ~ 21.00 m, depth excavation approximately 13.00 m from surface.
• Ventilation chamber and escape exit (from km 13+731.554 to km 13+743.505): open cut, reinforced concrete 100 cm-thick diaphragm walls, outer dimensions 27.50+22.50+12.50+15.00 m, height ~ 28.50 m, depth excavation approximately 22.00 m from surface.
• Open cut station “Cinisello-Monza” (from km 14+066.758 to km 14+184.712) and open cut artifact for future M5 line (from km 14+184.712 to km 14+200.668): lateral platforms station on three levels (platform, intermediate and mezzanine), depending from rail running depth (at about -18.00 m from surface, to underpass the future Line 5 extension having rail elevation at -12.00 m).
• Ventilation chamber and escape exit (km 14+556.666):  open cut, reinforced concrete 100 cm-thick diaphragm walls, outer dimensions 15.00 x 20.00 m, height ~ 32.50 m, depth excavation approximately 26.50 m from surface.

Excavation methods

To dig the tunnels, in the traditional method, a CAT 320 BM equipped with hydraulic hammer, ripper, erector, rotary cutting head and bucket will be used.

The excavation is carried out in partial section in presence of water according to the following steps: consolidation at the face in partial section; excavation, steel arches laying and shotcrete in partial section; consolidation and realization of the bench depending from the level of interference with groundwater excavation; excavation of the remaining section to the invert; waterproofing and realization of invert; final lining casting using a 9 m formwork of free-standing blanket/self-reacting mould

Muck haulage

The mucking-out is handled differently depending on the site zones. From artifact 'A4' will be realized a freight elevator in the shaft and all connections to the face will have a horizontal and vertical movement possible, with four axis dump trucks (as Iveco, Mercedes, Volvo). Those trucks will be used for the mucking-out at Cinisello-Monza station too, being the face served by a ramp.

At “Northern Bypass” site for the mucking-out a 4 cu m dumper will be used from face to the shaft, while for vertical translation a portal crane supplied by Tunnelservice will be used, equipped with a hopper and a 4 cu m hydraulic bucket loading from the shaft and discharging into a 40 cu m hopper that then loads the trucks.

Support and lining techniques

Pre-support of the face is by means of jet-grouting, also reinforced, using Puntel 1200 BEB and Puntel JET 1 drill rigs and a F.lli Dieci 50/21 telescopic handler, and steel arches. First phase lining with fibre-reinforced shotcrete with polyester fibers, Sika concrete admixture, while a CIFA Spritz system CSS 2 concrete pump has been used for shotcreting.

Waterproofing

Waterproofing is accomplished with double layer coat composed of smooth PVC sheets, 2 mm-thick, clearing and protection layers composed of TNT and smooth PVC 1.5 mm thick, supplied respectively by Sika, Mapei and Pavitex.

Click here for site photos and it/16 for tunnelbuilder archive. Visit www.metropolitanamilanese.it, www.cifa.com, www.utt-mapei.com and www.tunnelservice.it. 10/13.