Peter Kenyon, TunnelTalk
As the one millionth tonne of earth is removed from the ground for the £14.6 billion Crossrail project, and with the first TBM launched back in May 2012 just a few metres short of completing the first parallel tube of the 6.5km-long western tunnels, Peter Kenyon of Tunneltalk takes a closer look at progress on construction of the underground structures and 21km of twin-running tunnels that are currently being excavated under London.
- Preparations continue for relaunch of the two slurry TBMs from Woolwich that will drive under the River Thames and wrap up excavation work in the east as Crossrail prepares to celebrate reaching the landmark completion of half the 42km of running tunnels under London.
Completion of westbound crossover cavern at Stepney Green
- As of Tuesday (10 September 2013), Crossrail confirmed that the seven machines that are currently in the ground are just 2.15km short of notching up the landmark 21km figure.
- Meanwhile the western SCL crossover caverns at Stepney Green, where the main east-west alignment under the centre of the capital will branch northwards for the spur to the Pudding Mill portal and on to Shenfield, is complete (August 2013). The eastern cavern was finished in May (2013). Launch of the first of two TBMs (Jessica) from Pudding Mill that will break into the caverns at the end of their 2.7km southbound journeys has just taken place. The machine to bore the parallel tube (Ellie) will be the last of eight 7.1m diameter Herrenknecht TBMs to arrive from the factory in Germany, and preparations are currently under way for her delivery and assembly prior to a scheduled launch later this year (2013).
- Elsewhere on the project, refurbishment of the disused Victorian Connaught tunnel under the Royal Docks at the eastern end of the Crossrail slignment is at an advanced stage of completion following construction of the cofferdam to enable access to the tunnel from above for the first time since its original construction in 1878.
- "The EPBs are making very good progress and settlements have been below those designed for," said Professor Robert Mair, one of five experts on the five-man Crossrail advisory panel. "The crossover cavern at Stepney Green has just been completed and of course it is being very carefully monitored. I can honestly say that very little has come up on the project that was unexpected," Mair told TunnelTalk.
Fig 1. Map of Crossrail drives under London
- Eastern tunnels
1. Victoria Dock-Plumstead, Drive H
Breakthrough in late August (2013) into the Woolwich station box by TBM Mary marked completion of the first half of tunnelling on the 2.6km long section of Crossrail between Plumstead portal at the extreme eastern fringe of the alignment and the new station, north of the River Thames, at North Woolwich. Sister TBM Sophia, one of two slurry machines adapted for the wet ground of the eastern section, completed the same leg for the Hochtief/Murphy JV in May (2013), and is currently 200m (as at 10 September 2013) out of the station box following completion of a scheduled maintenance programme in preparation for the second half of the drive under the Thames.
2. Pudding Mill-Stepney Green, Drive Z
Eastern tunnels contract C305, held by the Dragados/ Sisk JV, covers excavation of the 2.7km northern spur from the Pudding Mill Lane portal back down towards the Stepney Green crossover caverns. Following completion of the giant caverns last month (August 2013) the first of two TBMs - TBM Jessica - was launched from Pudding Mill on her southern journey. As of 10 September (2013) she had completed 110m. Her sister machine, Ellie, is due to arrive on site from the Herrenknecht factory in Germany shortly and will be the last machine into the ground.
3. Limmo-Victoria Dock (Drive G)
This short section is just 0.9km long - but when breakthrough occurs in 2015 it will mark completion of all tunnelling and complete the vital link between the eastern and western tunnels. Excavation will be completed by TBM Jessica, as part of the C305 contract, after she has completed her drive into the Stepney Green cavern from Pudding Mill. From Stepney Green she will be pulled through to the Limmo tunnelling site, then pulled back to Limmo following first breakthrough for completion of the final parallel leg into Victoria Dock and completion of the 21km of twin running tunnels.
Timelapse video of Connaught Tunnel refurbishment
One of the innovative elements of Crossrail in the east involves the repair and refurbishment of the existing, but disused, Connaught Tunnel under the Royal Docks.
- Work on this contract by Vinci Construction was completed only this month (September 2013). The cofferdam constructed in July to hold back water and allow access to the disused tunnel for the first time since its construction in 1878 has just been reflooded with 13 million litres of water, and the dock reopened. Contractors had been working around the clock to ensure that they were able to meet a strict deadline for removal of the cofferdam in time to allow ships to pass through the dock ahead of a trade exhibition at ExCel in London during the first week of this month (September).
- The 1km-long Connaught Tunnel connects two short overground alignments that run back underground towards the east and under the Thames at the North Woolwich portal, and towards the west at the Victoria Dock portal and on into central London.
Draining 13 million litres of water from cofferdam (July 2013)
Widening and repair of Connaught Tunnel (August 2013)
- The Victorian tunnel formed part of the North London Line until it was closed in 2006, in need of urgent attention. In 1935, larger ships began scraping the bottom of the Royal Victoria Dock, below which the Connaught Tunnel sits. As part of work to deepen the dock at that time, the central section of the tunnel was narrowed, with brickwork removed and steel segments installed.
- This 550m section of twin running tunnel needed to be widened if it was to be able to accommodate Crossrail trains, in addition to extensive refurbishment of the entire 1km alignment, and in 2012 Vinci began advance preliminary investigations of the site prior to starting work on a dry refurbishment programme that involved installing a cofferdam to hold back the water and enable access from the top of the tunnel for the first time since the original construction was completed 135 years ago.
- "It was a race against the clock to get the work completed and the dock reflooded, so it's great news that we've got it finished ahead of schedule. It's been a fantastic effort by the whole team to get the job done safely, quickly and effectively," said Linda Miller, Connaught Tunnel Project Manager.
- Central Tunnels (Limmo-Farringdon Station, Drive Y)
TBM Victoria breakthrough at Canary Wharf station box
- Crossrail's longest drives, the 8.3km-long central tunnels between Limmo Peninsula in the east to Farringdon Station via Liverpool Street, Whitechapel and Canary Wharf Stations, launched in December 2012, with both machines breaking through into the Canary Wharf station box by the end of June (2013). Both are now back in the ground after scheduled maintenance and transit through the box to the opposite station wall. The contractor for this section is the Dragados/Sisk JV, and it forms part of the same Eastern Tunnels contract (C305) that covers the Limmo-Victoria Dock and Pudding Mill-Stepney Green drives.
- A spokesman told TunnelTalk that progress as at 10 September was 2.69km for TBM Elizabeth, and 2.15km for her sister machine, TBM Victoria.
Installing segments in western tunnel
- Western Tunnels (Royal Oak-Farringdon, Drive X)
- Meanwhile, the attack from the west by the BAM Nuttall/Ferrovial Agroman/Kier (BFK) JV (C300) is almost complete. TBM Phyllis, the first machine to be launched on the Crossrail project back in May last year (2012), is due imminently to break through on the final leg of her 6.5km journey from the Royal Oak portal just west of Paddington Station and into the station box wall at Farringdon. A Crossrail spokesman told Tunneltalk that Phyllis is just a few metres short of breakthrough, while sister machine TBM Ada, which launched in August 2012, is now at the 4.6km mark and has just under 2km of her drive remaining.
- Station construction
- More than £1.5 billion of the total investment in Crossrail is in new station infrastructure, the same amount that has been spent on the tunnel excavation contracts. At Paddington, in the west, a new station is being constructed next to the mainline station. Works have been completed on the construction of the station walls and the central concrete columns. The top concrete slab of the station has been cast and excavations have commenced below the slab. The station will ultimately be 22.2m deep.
- At Bond Street work is well underway at the two new Bond Street station ticket halls on Davies Street and Hanover Square and the 1.2km of mined passenger and service tunnels, while at Tottenham Court Road building continues on the Crossrail section of the new integrated eastern ticket hall at Charing Cross Road and the new western ticket hall at the corner of Dean Street and Oxford Street. Excavation of the western ticket hall is complete. Work has started on the 1.1 km of mined passenger, platform and service tunnels.
Crossrail stations and interchanges with underground and main line services
- The new Whitechapel Station is among the most architecturally ambitious on the Crossrail project. Key design elements include preserving the existing heritage station entrance with a more spacious forecourt area; a new ticket hall and larger concourse built above the London overground tracks; a new pedestrian walkway; and a more integrated station layout allowing easy, step-free interchanges between Crossrail, London Underground and London Overground.
Canary Wharf station has been designed to look like a ship in North Dock
- At Faringdon, work is well under way on two new Crossrail ticket halls. One will be integrated into the new Thameslink ticket hall when Crossrail opens in 2018. Works have also commenced on a new Farringdon ticket hall near Barbican station. Works on the passenger, platform and service tunnels have started. Both ticket halls are preparing for the arrival of the first two tunnelling machine from the west this winter. Four tunnelling machines, two from the east and two from the west, will finish their tunnelling journey at Farringdon.
- The new station at Liverpool Street will be located between the existing Liverpool Street and Moorgate stations. Crossrail will build two new entrances and ticket halls, creating new interchanges with the Northern, Central, Metropolitan, Circle and Hammersmith & City underground lines, as well as connections to Stansted Airport and National Rail services. The construction of the new western ticket hall is well under way and works on the new eastern ticket hall will begin in early 2014. More than 160m of new platform tunnels have been built so far.
- Canary Wharf Group began work on the new Canary Wharf Station in May 2009, building a station box 28m below the water surface of North Dock to create the ticket hall and platform levels. Above the new station Canary Wharf Group is delivering a four-storey retail development, topped by a roof top garden, community facility and restaurant semi-covered by a striking Foster-designed timber lattice roof. The main structural works above the station are complete - work is now focusing on the fit out of the upper levels which are intended to open in 2015, three years before the first trains are due to run.
Dry approach to Connaught Tunnel repair - TunnelTalk, February 2012
Station awards on Crossrail - TunnelTalk, February 2013
Crossrail clean sweep for Herrenknecht - TunnelTalk, September 2011
Site visit: Herrenknecht begins Crossrail TBM rollout - TunnelTalk, December 2011
Site visit: Crossrail Stepney Green junction caverns - TunnelTalk, September 2012
Crossrail launches first TBM - TunnelTalk, May 2012
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