London's power consumption rises by around three percent every year. Most of the power lines were installed in the 1950s at low depths which means that today they hardly offer any possibility to extend the grid in line with a sustainable energy policy.
"Cleopatra" started her journey at Eade Road in the north of London in December 2011: her mission is to build 12.4 kilometers of tunnel at depths of 20 to 60 meters. Cleopatra is an EPB Shield from Herrenknecht which is excavating one section of the 32-kilometer-long London Power Tunnels Phase One large scale-project. The segment moulds for the production of segments were supplied to London by Herrenknecht Formwork.
The larger interior diameters - four meters on Cleopatra's section - provide better access to the grid operators for maintenance and service work. On the other hand, they ensure that sufficient capacities will be available in future to extent the grid with new lines.
With the expertise from past tunnel drives in London’s typical clayey and sandy ground, the Herrenknecht engineers delivered the EPB Shield with three options for discharging the excavated material: the conventional discharge by screw conveyor from the invert as well as the possibility to discharge by screw conveyor or by belt conveyor from the center. The jobsite team celebrated Cleopatra‘s first project success with the breakthrough after the first section (around 7.8 kilometers) on April 30, 2013. The Herrenknecht EPB Shield drove up to 55.9 meters (43 rings) and up to 283.4 meters (218 rings) per week on this first leg.
From August 2013, the EPB Shield excavated the second leg, approx. 4.2 kilometers long, and arrived at the target shaft with the final breakthrough on May 21, 2014. The power cabels that will be installed in the new tunnel are expected to deliver energy to London’s inhabitants and businesses in 2018.