VERA (tunnel boring machine)

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The tunnel boring machine VERA - V on the E lbe R ichtung A lster - was on 15 May 2008 in the starting shaft at the future station Überseequartier the Hamburger Hochbahn by using mining tradition baptized and the Holy Barbara (patroness of miners and tunnel borer) by Bishop Maria Jepsen consecrated . Since then, VERA has been digging the two 2.8 km long tunnels at a maximum depth of 42 m under the Hamburg city center to the existing Jungfernstieg underground station for the new, initially four-kilometer-long U4 underground line  using the shield driving method .

Working method

40 weeks were estimated for each “trip”. The completion of the first tube, planned for spring 2009, was postponed to October 2009. Work on the second tube began with the christening of the machine in early January 2010. In front of the jetty on Jungfernstieg in the Inner Alster , the drill head is then separated and lifted out - specially To do this, the underwater station, which was sealed against ingress of water, had to be opened through a sheet pile wall - and transported back to HafenCity , while the actual shield driving machine (the “back-up”) was withdrawn through the tunnel in order to tackle the second tube (reunited with the drill head) .

The cutting wheel of the drill alone - with an outer diameter of 6.57 meters larger than the finished inner diameter of the tunnel - weighs just under 62 tons including the axle, the complete shield driving machine is around 74 meters long and has a total weight of 650 tons. This device, which costs more than seven million euros - always a one-off production for the respective task and soil condition - was developed by the Herrenknecht company from Schwanau and achieves a tunneling of around 10 meters in 24 hours.

Powerful electric motors drive the heavy cutting wheel with roller chisels, paring knives and scrapers, which is under overpressure against water ingress, and press it against the earth, the so-called face . Large stones are automatically sorted out and smashed, only larger boulders (> 50 cm) also have to be broken up “by hand”. The whole with a bentonite - suspension (also serves as a support fluid against the pressure of the masses of earth and prevents by its specific gravity from penetrating groundwater) liquefied waste is then pumped out and disposed of in the starting shaft, so the choice of drilling direction from the port towards the city center: Convenient removal and supply without major traffic disruption from the construction site.

The bentonite suspension acts thixotropically : if it is shaken or swirled in a vessel, it reacts like a liquid and flows. If, on the other hand, it comes to rest for a moment, the vessel can be turned around and nothing will run out: it appears to remain stationary when it is at rest. In this way, rapid removal by pipeline through the continuously growing tunnel is achieved in a continuous cycle: the overburden is removed again by a centrifuge in the separation plant near the start shaft and removed separately, the cleaned suspension can now be used again and is returned to the Pumped face.

Simultaneously with the progress of clearing, the tunnel tube is lined with tubbings by the erector integrated in the driving machine . This huge mechanical arm lifts the reinforced concrete parts to the freshly dug tunnel wall in a precisely defined order. For replenishment, a small truck transports the reinforced concrete components to the machine, where a crane lifts them onto a conveyor belt that transports the segments to the erector. At VERA, seven of these rounded, approximately 1.50 m wide and 3.8 t heavy concrete elements form a circular tunnel ring. The tunnel boring machine's hydraulic presses then apply to this segment ring that has just been laid in order to push the entire machine further forward. The concrete segments are calculated and manufactured so precisely that the tunnel ring may only deviate from the specified dimension by a maximum of 10 mm so that the tube remains perfectly fitting.

Name search

By April 22, 2008, the Hamburger Hochbahn received over 1200 name suggestions for the tunnel boring machine. Over 60% of the votes fell on VERA. This was the second time that a tunnel boring machine used in or below Hamburg was given a name: From October 1997, TRUDE did a “good job” in the construction of the fourth Elbe tunnel tube . When a shield driving machine was used for the first time in Hamburg (the first tunnel in shield driving was the old Elbe tunnel in 1907 ) - crossing under the long-distance railway tracks in 1958/59 to the south of the main station on the U1 subway line  - no names were common.

Web links

Individual evidence

  1. ↑ Celebratory tunnel baptism in HafenCity ( Memento from January 20, 2010 in the Internet Archive )