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Crossrail Project: Machine-Driven Tunnels on the Elizabeth Line, London

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Crossrail Project: Machine-Driven Tunnels on the Elizabeth Line, London Civil Engineering Proceedings of the Institution of Civil Engineers Volume 170 Issue CE5 Civil Engineering 170 May 2017 Issue CE5 Pages 31–38 http://dx.doi.org/10.1680/jcien.16.00028 Crossrail project: machine-driven Paper 1600028 tunnels on the Elizabeth line, London Received 11/07/2016 Accepted 16/12/2016 Keywords: concrete structures/excavation/tunnels & King, Thomas and Stenning tunnelling ICE Publishing: All rights reserved Crossrail project: machine-driven tunnels on the Elizabeth line, London 1 Mike King BSc, CEng, MICE 3 Andy Stenning BSc, PhD, CPEng, MIEAust, MHKIE, MASCE Technical and Compliance Director - Tunnels, CH2M, London, UK Technical Director, Atkins Ltd, London, UK 2 Ivor Thomas BEng, LLB, CEng, FICE Tunnel Manager, BAM Nuttall, London, UK 1 2 3 The 42 km of tunnels constructed using soft-ground pressure-balance tunnel-boring machines for London’s new Elizabeth line were completed over a 3 year period. A single lining design solution was developed for all tunnels using a fully gasketed, steel-fibre-reinforced, concrete segmental lining suitable for use in all potential ground conditions anticipated along the alignment. The £14·8 billion Crossrail project faced many challenges, including dealing with significant quantities of different excavated material while minimising the environmental impact from transportation and disposal, minimising settlement effects and dealing with multiple tunnel-boring machine launches and receptions. This paper addresses how the issues were tackled and comments on the tunnel-boring machine design and the approach taken for survey control. Outline figures are also provided for the tunnelling rates. Finally, some conclusions and recommendations are made based on the observations and lessons learnt during the project. 1. Introduction and to control ground movements under sensitive structures and close to underground assets, including existing operational metro The £14·8 billion Crossrail project to deliver the 118 km lines and old utilities sensitive to disturbance. Elizabeth line across London, UK, required 21 km of twin running Of the eight TBMs, six were earth-pressure-balance machines tunnels in the central part of the route (Tucker, 2017). They were (EPBMs) and two were slurry shield machines, which were for constructed using a total of eight tunnel-boring machines (TBMs) use in the water-bearing Chalk aquifer. The drives were let in three working in five sets of parallel tunnel drives, as shown in Figure 1. main tunnel contracts, with details as shown in Table 1. Pressure-balance TBMs were adopted across the whole project Tunnel construction extended over a 3 year period, with the final to deal with the ground and groundwater conditions anticipated, TBM on drive Y arriving at Farringdon station in May 2015. To Shenfield N Straford Pudding Mill Lane Paddington Bond StreetTottenham Court RoadFarringdon Liverpool Street Whitechapel To Reading Completed Completed Stepney GreenJESSICA (D1) and Heathrow 27/01/14 10/05/15 caverns ELLIE Completed 13/02/14 Canary Wharf Limmo PeninsulaVictoriaCustom Docktunnelling House site North Woolwich ADA Completed Completed ELLIE Connaught tunnel 07/10/13 Completed (D2) 26/05/15 13/06/14 ELIZABETH PHYLLIS Royal Oak JESSICA Completed 22/05/14 Drive Y Completed (D2) Drive X VICTORIA 05/08/14 Drive Z Completed Completed 18/10/14 Woolwich To Abbey 29/01/14 MARY Wood Drive G River Thames SOPHIA Drive H 0 km 2 Plumstead Figure 1. Plan of central tunnelled section showing TBM drives 31 Civil Engineering Crossrail project: machine-driven tunnels Volume 170 Issue CE5 on the Elizabeth line, London King, Thomas and Stenning Table 1. TBM contract details Contract Drive Location TBM type Length: km C300 X Royal Oak to Farringdon Earth pressure balance 6·8 C305 Y Limmo to Farringdon Earth pressure balance 7·9 Z Pudding Mill Lane to Stepney Green Earth pressure balance 2·7 G Limmo to Victoria Dock Earth pressure balance 0·9 C310 H Plumstead to North Woolwich Slurry 2·8 2. Ground conditions Lambeth Group with the face mainly in the clay. The alignment dropped the tunnels into the Lambeth Group before rising again The typical geological sequence under London, and the general into the London Clay, where they remained until the tunnels description of the strata encountered along the route, are shown in completed their drive at Stepney Green. Table 2 (Black, 2017). The main strata encountered by the TBMs Drive G was launched from Limmo shaft in London Clay. along each drive length are summarised below, with descriptions The TBMs remained in the clay with only occasional Lambeth given in the direction of TBM drive, and shown in Figure 2. Group strata in the invert until arriving at Victoria Dock portal In drive X, from the Royal Oak portal, the tunnels were launched where the crown of the tunnels intersected treated layers of River in River Terrace Deposits before moving into the London Clay, Terrace Deposits. continuing in this stratum as far as the Fisher Street crossover, The drive H TBMs launched in Plumstead at the interface where the Soho anticline brings Palaeocene strata closer to the between the Thanet Sand and the Chalk, dropping down into the surface. Here the tunnel alignment dropped into the Lambeth Group Chalk for the majority of the route, only rising into the Thanet clays and sands. The tunnels just entered the lower Lambeth Group Sands either side of Woolwich station. As the tunnels ascended to sands, gravels and silts as they progressed into Farringdon station. the reception point at North Woolwich portal, the face was again On drive Y, at Limmo shaft the tunnels started in London Clay moving partially into the River Terrace Deposits. but quickly passed through the Lambeth Group upper and lower units before partially entering the Thanet Sands. The tunnels followed the lower Lambeth Group/Thanet Sand boundary until 3. Health, safety and welfare the Stepney Green area, where the tunnels moved back into the London Clay, and in which they remained until part way between Analysis of all incidents, near misses and accidents during the Whitechapel and Liverpool Street stations. At this point the Crossrail tunnelling drives provides a breakdown of risk type as tunnel alignment descended and they continued with mixed face shown in Figure 3. conditions of London Clay and Lambeth Group up to the east end Occupational health nurses were provided by the contractors at of Farringdon station where the drive terminated and the machines all tunnelling sites and proved their worth time and time again. were dismantled. Shift patterns varied, with most of the contractors working two Drive Z started at the Pudding Mill Lane portal. The TBMs 12 h shifts a day in a seven day week, the exception being in the launched at the interface between the London Clay and the west where the contractor chose to work three 8 h shifts a day. Table 2. Ground conditions on route alignment Strata Typical description Typical thickness : m Made ground Variable 2 to 5 Alluvium Soft to firm, sandy, slightly gravelly, organic silty clay 1·5 River Terrace Deposits Medium-dense fine to coarse sand and gravel with rare cobbles and flints. Perched water table above 1 to 2 London Clay London Clay Firm to very stiff fissured clay with silt partings and laminations. Considered an aquitard not 5 to 23 containing significant quantities of groundwater Lambeth Group Variable sub-strata varying from stiff to hard (possibly friable), closely fissured, sandy to very sandy 11 to 20 clay, to stiff to very stiff silty to very silty clay. The Upnor Formation at the base of the Group varies from very stiff sandy silty clay to very dense clayey silty fine to coarse sand. Lower clay content layers are associated with higher permeability and connectivity with lower water-bearing layers Thanet Sand Very dense, silty, fine and medium sand. Highly permeable and in hydraulic connectivity with 3 to 15 underlying chalk Chalk Medium density, weak to moderately weak, fractured chalk with flint bands. Contains large – quantities of water 32 Civil Engineering Crossrail project: machine-driven tunnels Volume 170 Issue CE5 on the Elizabeth line, London King, Thomas and Stenning Zone of faulting Drive X Drive Y Drive Z Paddington station Bond Street station Tottenham Court Road station Fisher Street shaft/cross-over Farringdon station Liverpool Street station Whitechapel station Stepney Green junction Grand Union canal Mile End Park shaft Eleanor Street shaft River Lea Pudding Mill Lane portal Royal Oak portal 120 110 100 90 80 70 60 50 Height above tunnel datum: m 40 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10 000 11 000 12 000 13 000 14 000 14 500 Distance along tunnel drive: m Zone of faulting Zone of faulting Greenwich fault zone Drive Y Drive G Drive G Superficial deposits River Terrace Deposits London Clay (including Harwich Formation) Lambeth Group Mid-Lambeth Hiatus Thanet Sand Canary Wharf station Stepney Green junction Poplar Dock River Lea Limmo Peninsula shaft Victoria Dock portal Custom House station North Woolwich portal Woolwich station Plumstead shaft Plumstead portal Chalk River Thames 120 West India Dock Connaught tunnel Deep aquifer piezometric 110 100 90 level (August 2008) 80 70 Eastbound tunnel 60 50 Westbound tunnel Height above tunnel datum: m 40 11 000 12 000 13 000 14 000 15 000 16 000 17 000 18 000 19 000 20 000 21 000 22 000 23 000 Distance along tunnel drive: m Figure 2. Geological long-sections of tunnel drives for the railway, track form, evacuation and emergency walkways liptripfall 1 Struck by moving machinery 24% and to accommodate the necessary in-tunnel systems and services Lifting operation 17% (Figure 4). Manual handling 9% The excavated diameter of the tunnels was approximately 7·1 m, Pressure systems/ allowing a 6·2 m internal diameter (6·8 m external diameter) precast sprayed concrete lining 7% Tunnel-boring machine 6% concrete segmental lining to be erected, with the annulus between Contact with buried service 2% lining and ground filled with grout injected through the TBM skin.
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