BTS | HARDING PRIZE COMPETITION 2023
LAUNCH SYSTEM AT SILVERTOWN
PRESSURE RING
The Harding Prize Competition is named after the founder of the British Tunnelling Society, Sir Harold Harding, and is for entrants under the age of 33. Shortlisted papers were presented to the BTS evening meeting on 13 April, at the Institution of Civil Engineers, in London.
Ricardo Manias García, senior mechanical engineer with Riverlinx CJV, was a runner-up in this year’s Competition with a paper entitled ‘The Pressure Ring Launch System at the Silvertown Tunnel Project’. It is published here with the author’s permission
The Silvertown Tunnel Project will be a 1.4km-long road link under the River Thames linking Silvertown with the Greenwich Peninsula in East London. The twin-tube’s tunnels are 10.8m i.d. and are under construction. The scheme’s purpose is to relieve the traffic congestion near the Blackwall Tunnel and allow better public transport links, including more cross river bus journeys. Transport for London (TfL) contracted with the
Riverlinx Construction Joint Venture (CJV) – a joint venture of Ferrovial Construction UK, BAM Nuttall and SK Ecoplant – to build the tunnels and approaches to the existing roads. The Riverlinx CJV instructed to tunnel boring
machine (TBM) manufacturer Herrenknecht to design and fabricate the largest TBM built for the UK, with an excavation diameter of 11.91m, to perform the tunnel construction. The single TBM is of earth pressure balance machine (EPB) type and is driving both of the link’s parallel tunnels. In September 2022, the machine was launched from
the Silvertown site, on the north side of the river, to excavate the Southbound drive towards the Greenwich peninsula. Upon arrival at Greenwich, the TBM would be rotated using nitrogen cushions, sliding it around inside the shaft into re-launch position. The machine would then excavate the northbound tunnel back to Silvertown, where it will be dismantled.
WHY USE THE PRESSURE RING FOR TBM LAUNCH? The Pressure Ring System of launching allows the large TBM to be launched, twice, in compact shafts on either side of the river. The shafts were sized to the minimum because of neighbouring land use and the proximity of a disused lock entrance in Silvertown. A more common rectangular shaft was dismissed at
Above figure 1: Aerial view of the ‘peanut’ shaft, the TBM, launching structures and conveyor belt
20 | June 2023
Silvertown site because of the complexity of design and execution. An alternative layout of a four intersecting shaft cells that would create the shape of a ‘peanut’ was chosen.
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