EPBM supplied for Rio's metro Line 4

10 October 2012

A TBM with a 11.46m diameter has been supplied for the construction of the new metro Line 4 in Rio de Janeiro, Brazil. Brazilian construction companies Construtora Norberto Odebrecht S.A/Construtora Queiroz Galvao S.A/Carioca Christiani Nielsen Engenharia has accepted the Herrenknecht AG machine, which will be used to bore a 4.6km long section of the 14km metro line.

The Herrenknecht EPBM will tunnel the stretch between the Gavea and General Osorio Stations, and will be the first TBM ever used in Rio, with all previous underground construction works built using conventional techniques or as cut-and-cover tunnels. It is hoped the project will contribute to relieving the traffic routes in the metropolitan area.

The construction team will bore through ground conditions consisting of sand and Gneiss while erecting a pre-cast concrete segmental lining. To ensure the machine can cope with the different ground conditions along the tunnel route, the Herrenknecht engineers designed it so it can be converted in the tunnel.

"It is planned that the machine will cover the first 300m in open mode, then be converted for about 3,000m in closed EPB mode," said Carlos Manzano Rey, Herrenknecht project manager. "Finally, around 1,300m will again be tunnelled in open mode." In open mode, the firm hard rock is transported away on a conveyor belt. In closed EPB mode removal is handled via a screw conveyor in the predominantly andy soil. Another feature of the TBM is the articulation in a diameter range of more than 11m, which will allow the tunnelling teams to cope with the tight bend radius of 250m in some cases.