Trude, the world’s largest shielded tunnelling machine, at 14.2m diameter, has broken through on the 2.6km long 4th Elbe highway link tunnel in Hamburg, Germany. The event occurred on March 2 2000 and was witnessed by numerous prominent politicians, including Hamburg’s mayor, Ortwin Runde.

Contractor Arge 4 Röhre Elbetunnel (ARGE 4) started tunnelling on the $421.1m project using the giant Herrenknecht machine in October 1997 from the south bank of the Elbe River. The JV achieved construction rates of up to 14m/24h day. After two years and five months, the slurry mode TBM emerged precisely on target in the end shaft in Hamburg Othmarschen.

The large diameter tunnel is lined by 2m wide x 700mm thick segments and a total of 11 448 were used along the full 2.6km length.

Speaking of the event, Martin Herrenknecht, managing director of Herrenknecht AG, says, "With Trude’s breakthrough, a new milestone in modern tunnel construction has been reached. The enormous diameter of the tunnel; the complex ground conditions; passages with little overburden; and retaining pressures of up to 5 bar – all placed large demands on the machine and the ARGE 4 project management."

The 4th Elbe tunnel is said to be the biggest tunnel in the world constructed underwater with a shielded tunnelling machine and is due to open to traffic in 2002. It is the first of the four tunnels under the Elbe to be bored, the other three being immersed tubes. Boring was deemed the only feasible method of construction as disruption to the shipping traffic on the river was unacceptable.

As predicted in T&T International in January, the TBM will now be disassembled and transported back to the Herrenknecht factory in Schwanau. It will undergo maintenance before delivery to Moscow for work on the 3.2km long city motorway tunnel.