east london line ReBoRn MaJoR PRoJeCt RePoRt -...

east london line ReBoRnMaJoR PRoJeCt RePoRt27|05|10

london’s new RailwayPLanning, design and construction of a new 10km raiL route for London overground

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EAST LONDON LINE: INTRODUCTION

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upgrade the East London Un-derground Line that ran from Shoreditch to New Cross Gate since 1997. London Underground had the idea to take a railway into Hackney on a disused viaduct that had once carried the North London Overground Line from Broad Street Station, which had disappeared under the Broadgate development in 1986.

It got Transport & Works Act (TWA) powers for the scheme, which was then expanded again when it was realised the railway could interconnect with the North London Line. Another Transport & Works Act was ac-quired, and as the project by that stage had effectively become part of Overground rather than Underground rail, it was passed to the newly formed Strategic Rail Authority (SRA) to manage.

ELL plans languished there without a champion. But over at Transport for London it did have its backers – Smith and his managing director Ian Brown at TfL’s developing London Rail division in particular. And when the SRA wound up and the route was bequeathed to TfL in 2004 they fought for, and won the funding.

“There was pressure to make a decision as the TWA powers

were about to run out, and then the Olympics came along, which finally tipped the balance and we could get on with building the project,” Smith says.

Peter Richards was brought in from the SRA to run the job as infrastructure director for the now dubbed London Over-ground, along with Mike Stubbs as engineering director, and they got stuck into design.

There had been a brief flirta-tion with funding the route through private finance. “But the ELL is a grey asset,” Smith says. “There is a lot of old in-frastructure it would have been difficult to box up for PFI, and a PFI takes time to put together.” With the 2012 Olympics fast ap-proaching, it was decided to go for a design and build option.

It was a good decision. The scheme, built by a Balfour Beatty Carillion joint venture (BBCJV), opened early on 23 May. BBCJV won the contract in October 2006, started design immedi-ately, and then started the major structures in 2007. It got onto the tunnel and south sections of the site when the old East London Underground was closed in December 2007 and handed over in late January 2008.

“From the start, we stressed to everyone that this job is about delivering an operational railway – infrastructure, rolling stock and operations,” says Richards. “We have managed the integra-tion between these aspects and given the responsibility for man-aging the interface between the

existing infrastructure and main works structures and rail sys-tems to Balfour Beatty Carillion as our main works contractor.

“That is why we went for a single NEC3 design and build main works contract.

“It has meant that BBCJV has managed the interfaces, and all the responsibility has rested with one party to get on and do the whole thing.”

When Richards set up the job he wanted to create momentum, so he formed an integrated client team to manage the job and drive its progress. This included himself, Parsons Brincker-hoff’s Ashok Kothari as head of programme management and designers from Mott MacDonald as technical adviser to the project.

Refurbishment work along the route on some of the older structures like the Kingsland Viaduct was let as enabling works contracts to Murphy and Taylor Woodrow (now Vinci Construction).

“Refurbishment is risky and it was prudent to do some of that first before we let the bigger contract,” Richards says.

“And then, as a client team, we worked very hard towards letting the main works contract to programme.

“We didn’t let ourselves slip. By doing that we created float for the rest of the project and that has helped us come in early. We are delighted to have opened on 23 May, ahead of a pro-gramme set back in 2004.”

One day after the opening of the core route of the London Overground East

London Line last month, pas-sengers were wandering around wide-eyed, taking in the wonder of the capital’s newest rail route.

Londoners who know the detail of the Underground better than their bank pin numbers were cooing contentedly to themselves while looking at a map of the route which revealed a whole new circuit board of travel possibilities. As the first section of ELL opened they could go from Dalston in Hack-ney in the north, south to the Docklands at Canada Water and then on to New Cross. From this week, since the full line opened on 23 May, the route will take them as far into the south Lon-don suburbs as West Croydon and Crystal Palace.

By early next year when phase 1a of the East London Line opens, Croydon will have a direct connection to Highbury and Islington, and at Dalston travel-lers will be able to switch onto a newly upgraded North London Line to go east to Stratford and the Olympics or west to Willes-den Junction and Richmond. And by 2012, construction of a link from the East London Line

at Surrey Quays to railway at Old Kent Road will allow a western trip to Clapham Junction via Peckham Rye and Wandsworth Road and link to the Overground Clapham Junction to Willesden Junction Line.

The capital will have an outer orbital metro railway under the banner of London Overground, interconnecting along the way with its Underground lines and serving 20 of its 33 boroughs; and commuters will have oppor-tunities aplenty to avoid central bottlenecks when they are trying to cross the city.

The key to creating this will have been a £1bn Transport for London investment in infra-structure and new rolling stock. This has reinvigorated and expanded the old East London Line Tube line, reusing Victorian infrastructure and introducing some new modern landmarks along the way.

There are going to be huge benefits in terms of regeneration and new jobs for some of the less developed parts of the City, rail-deprived Hackney will at last have a metro, and east and southeast London will acquire some life changing infrastruc-ture.

Around 33M passengers are expected to be using the route every year by 2011, rising to a projected 39M by 2016.

“The really good part of this job,” says London Rail chief executive Howard Smith, under who’s remit the East London Line falls, “is that we are chang-ing the face of London and the way we think of and use London in a permanent way. It is really dramatic.”

There has been a plan to

east endefficiencyThis week the London Overground East London Line opened a full service from West Croydon in south London to Dalston in the north. In a remarkable achievement, the project has been delivered early. Jackie Whitelaw reports.

“As a client team, we worked very hard towards letting the main works contract to programme” Peter Richards, infrastructure director London Overground

“We are changing the face of London and the way we think of and use London in a permanent way. It is really dramatic” Howard Smith, London Rail

Client London Overground for Transport for LondonOther parties London Underground, Network RailContractor Balfour Beatty Carillion joint venture (BBCJV)Contractor’s designers Scott Wilson, Tony Gee & PartnersProgramme manager Parsons BrinckerhoffClient’s technical adviser Mott MacDonaldRolling stock BombardierOperator LOROL

Signalling,communications and power systems, 3.5km of new or refurbished viaduct from Whitechapel to Dalston Junction; 3.2km of track in tunnel south of Whitechapel to Surrey Quay

New stations at Dalston Junction, Haggerston, Hoxton and Shoreditch High Street; refurbishments at Whitechapel, Shadwell, Wapping, Rotherhithe and Surrey Quays; an operational control centre; depot; and 44 four car Electrostar 378 trains – 20 for the East London Line and 24 for the North London Line.

WHO’S WHO

EAST LONDON LINE IN BRIEF

StratfordDalston JunctionHaggerston

Hoxton

Shoreditch High Street

Highbury &Islington

Blackhorse Road

Whitechapel

GospelOak

Shadwell

Canada WaterSurrey Quays

Queens RoadPeckham

Denmark Hill

West Brompton

Kensington (Olympia)

Shepherd’s Bush

EustonKensal GreenQueen’s Park

CENTRAL LONDON

WillesdenJunction

West Hampstead

Harlesden

Stonebridge Park

ClaphamHigh Street

KewGardens

Gunnersbury

ClaphamJunction

New Cross

Brockley

Honor Oak Park

Forest Hill

Sydenham

Penge WestAnerley

Norwood Junction

Crystal Palace

West Croydon

NewCrossGate

PeckhamRye

North West to WatfordJunction

East toBarking

To Richmond

KEYPhase 1 opened 23 May 2010

Phase 1a completed by 2011

Phase 2 completed by 2012

OVERGROUND

East London Line is vital for creatingan outer orbital railway around thecapital. Phase 1 opened on 23 May.

City slicker: The East London Line is a vital new link to London’s financial heart

EAST LONDON LINE REBORNMAJOR PROJECT REPORT

LONDON OVERGROUND: THE FUTURE

venture finally got onto the line three months early at the end of January 2008.

That is when the scope of the job began to develop. There was the depot to add in. And two bulk supply points for power. “Those two 132kV bulk supply points came on top of three 33kV traction substations already in the contract, and those three had to change from pre-assembly to larger built insitu on site versions,” says Balfour Beatty Carillion construction director Adam Stuart.

An enabling works contract had beefed up the Victorian Kingsland brick arch viaduct between Shoreditch High Street and Dalston. “But that still left BBCJV a lot of work in further assessment and strengthening,” says Stuart.

The six “tunnel” stations between Whitechapel and Surrey Quays also needed much more work than originally thought and London Over-ground decided to properly refurbish them, he adds.

“A grade separated junction was also introduced to make the link with phase 2 to Clapham Junction so as not to disrupt

East London Line running when that project goes ahead.

“One of the things I am most proud of here is that the scope has increased very significantly yet our design, construction and commissioning period increased by only five months,” says Stuart.

BBCJV drove itself along, and for added momentum it had a set of about one hundred non-contractual milestones to hit, worked out with Parsons Brinckerhoff.

“In December 2008 we said that we’d have all the structures, track, and operational systems complete to start test train running 10 months later on 5 October 09, and we did,” says Stuart. “And from that date we ran up to six of the new trains every day for four months during which we finished the new station buildings behind the platforms; our track gives a very smooth ride and the Invensys signalling system proved fault-less.”

“Also in December 2008 we gave a date of 17 January 2010 to hand over to trial operations and on that very date we started the week long process of handover to Transport for London for trial operations,” adds Casebourne. “In parallel the refurbishment of the tunnel stations was completed and the customer information systems were finished. Now customers are on board and everything is working reliably.”

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EAST LONDON LINE: MaNaGEMENt

What is remark-able about the management of the London

Overground East London Line construction work is that the job has so successfully beaten its deadlines; particularly when the scope of the scheme was some-what fluid when the job was tendered.

Balfour Beatty Carillion Joint Venture (BBCJV) bid for and won the basic project against strong competition and with the addition of many changes. The final job is coming in at £700M or thereabouts after new elements were added in and the amount of work required became clearer as the construction teams got stuck in on site.

“We knew there would be additional work in the central section but we couldn’t find out how much until we took posses-sion of the railway from London Underground (LUL),” says London Overground Infrastruc-ture director Peter Richards. “We also knew the depot, for instance, had to be added in but the contractor could not price that in the original tender because the designs from [rolling stock supplier] Bombar-dier were still being developed.

“That is why we went for a target cost design and build contract rather than fixed price.”

But Richards points out that there was always a total budget and as the work grew, “we adjusted the scope to suit the budget.”

“Is it safety critical?” was the mantra. If it was, then the money was found, if not, then as much cash was saved on each opera-tion as possible so there was some to spare when needed.

That approach required close collaboration between the client team, BBCJV and its supply chain throughout the works.

“The closely cooperative culture of the job has been vital,” says Balfour Beatty Carillion project director Mike Case-bourne. “It is one of complete openness; no secrets, shared decisions and facing and solving problems together.”

Richards agrees: “We have some very dedicated people on this project. There is a collabora-tive, positive culture which has all helped towards getting the job out the door on time and on budget.”

Actually the railway is two months ahead of schedule. The original opening date set at the start of the job in 2004 was 30 June 2010. The full line opened on 23 May to coincide with the seasonal timetable change; and passengers were using the central section of the route from 27 April. Not bad for a complex, modern railway squeezed into a packed capital city.

“We are particularly pleased about getting the route into service early as it will have a huge benefit to the travelling

public,” Richards says. “Right from the start,

when we signed the contract on 20 October 2006 we had to remember that we had committed to design, construct, test, commission and deliver an operational railway, not just its separate structures and rail

systems,” says Casebourne. “It was a requirement driven

contract – for example to design for three minute headways between trains.”

“There were 6,000 require-ments and about two thirds of them were changed or modified as we all got on with the job,” says Balfour Beatty Carillion engineering director Andy Nettleton. “Without strong management of a resilient, responsive design organisation we would never have achieved so much in such a short time.”

The key to pinning down the scope was gaining access to the old Underground section of the route between Shoreditch and New Cross Gate.

“We pushed to get London Underground to agree to get the route closed as early as possible,” says Parsons Brinckerhoff head of programme management Ashok Kothari . LU agreed to shut down the line in December 2007 although it had originally wanted to keep it open until the following April.

There was a slight delay while Underground upgrade contractor Metronet stripped out all of its assets but the joint

Working TogeTheras a Team

SAFETY

The London Overground East London Line scheme has had an excellent safety record over the duration of the project.

The site has twice recorded 1M accident free hours under the Reporting of Injuries, Diseases and Dangerous Occurrences Regulations (Riddor) 1995.

This was achieved in December 2008 and again in November 2009.

The job hit over 1.5M continuous Riddor-free hours, and the current accident frequency ratio of reportable accidents to 100,000 man hours worked is an excellent 0.12, a performance which recently landed a coveted Rospa Gold Award.

“We have had a really big push on the safety culture on this project,” says health and safety manager Mike Davies.

“We have focused on the supervisors and gangers and put in some fun incentives like group of the month winning a fleece each,” he adds.

Collaboration between client, contractor and supply chain was crucial as the construction project developed in scope, writes Jackie Whitelaw.

MANAGING THE TEAMS

COMMUNITY RELATIONS

As BBCJV project director, Mike Casebourne has had to manage 640 professional staff, and 600 designers off site in the offices of Scott Wilson and Tony Gee and other designers.

He is aslo responsible for 2,500 operatives on site at peak and up to 1,000 people engaged in the offsite manufacture of all the elements for the job all over the UK. At peak, the project was spending £30M every four weeks

or £1.5M a day. The job was divided into four

construction sections under the control of four BBCJV senior project managers; northern civils under Andy Swift; southern and central civils under Paul Rasmussen; rail systems under Elliott Young and the depot under Howard Williams. These were supported by design, commercial and administrative managers within their teams and reporting also to their department directors.

“We had to design, construct, test, commission and deliver an operational railway” Mike Casebourne, BBCJV

“The scope increased, yet our design, construction and commissioning period increased by only five months” Adam Stuart, BBCJV

Team work: The close cooperation culture of the job has been vital to successful construction of complex projects like Dalston Junction station

Community relations were a vital part of successful delivery of the East London Line with full time community relations managers working for London Overground and BBCJV.

The usual issues of working hours, noise and dust had to be addressed but it was either end of the project – at Dalston and New Cross Gate where there were most sensitivities. “There was some resistance to the idea of Dalston being gentrified,”

says head of communications for London Rail Julie Dixon. “But we always stress that the East London Line is a regenerating railway with the priority being to give people access to jobs which has helped allay concern.“At New Cross Gate people were unhappy at the idea of a 24 hour train depot. The solution was to get the residents involved, listen to them and respond to their concerns. For instance, the depot will have low level lighting so as not to create a nuisance.”


EAST LONDON LINE: DALSTON & NORTHERN STRUCTURES

Dalston Junction station is a massive, complex structure that has been designed to support multi-storey buildings and to accommodate the potential Crossrail 2 line, as Margo Cole discovers. And Adrian Greeman focuses on the array of civil engineering work in the northern section linking the Victorian Kingsland Viaduct to the old East London Line at Whitechapel.

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In theory, building a new four-track four-platform station at Dalston Junction could have been fairly

straightforward. Admittedly, space was very

tight, but the new line runs through an existing cutting, so surely it wouldn’t have been too much of a challenge to build a roof slab over a section of the tracks and put a station building on top – would it?

The reality is not quite so simple. The area taken up by the railway line as it runs through the heart of Dalston is prime development land and an important area within Hackney’s regeneration plans. As a result, a slab had to be built over the tracks not only to support the station building but also the loads from a series of apartment

blocks of up to 17 storeys that are set to be constructed on top.

Within weeks of work starting, what had once appeared to be a generously-proportioned, open cutting had become a highly congested construction site, with over 30 pieces of major plant involved in excavation and pile installation, as the London Over-ground East London Line team set about building a 250m long by 40m wide podium slab and its supports.

The loads from the proposed apartment blocks will go into downstand beams built into the 500mm thick podium slab, and from there into a series of walls and columns supported by deep piled foundations. The new plat-forms will sit under the podium slab, just above pile cap level.

For the most part, the down-stand beams are 1m deep, and were cast in situ along with the deck slab. Some of the beams were very heavily reinforced, as BBCJV section manager

for Dalston Kingsland Guy Anstiss recalls. “In some places there’s an awesome amount of reinforcing steel. One section of beam has over 100 H40 bars at the top and bottom of the downstand beam, and multiple

links,” he says.This gives a total of 1,250kg of reinforcement per linear metre in some locations.

However, in 19 beams, even this heavily reinforced concrete was unable to support the anticipated point loads from the

apartment building which are expected to be up to 7,000t. Here, steel I-beams have been used as part of the permanent reinforce-ment, with pairs of I-beams joined top and bottom with diaphragm plates.

These pairs of beams weigh up to 90t each, and span up to 33m. They sit on specially designed bearings supplied by Freyssinet that weigh up to 3t and are capable of handling the uplift and the rotation that could

be caused by such heavy point loads. Once the beams were in place, the diaphragm plates were welded insitu, the voids between the plates were filled with grout and then reinforcement cages placed in and around the beams to tie them into the podium slab before the concrete was poured. In all, there is 1,000t of structural steelwork in the new station, most of it in these massive beams.

The downstand beams span between walls and columns that sit on pile caps up to 2m deep, the largest of which takes up an area of 3,600m2. Beneath the pile caps are heavily reinforced bored concrete bearing piles, most of which are 650mm or 750mm in diameter, and sunk to a depth of 26m. However, at one end of the site, provision has been made for the possibility of the second Crossrail line passing diagonally beneath the East London Line.

In the original design, a raft foundation would have

River ThamesWAPPING

View along the Thames Tunnel, c. 1835

ROTHERHITHE

HIGH WATERLOW WATER

Section

Masonryconstruction

River ThamesWAPPING


ROTHERHITHE

HIGH WATERLOW WATER

Section

Masonryconstruction

WhitechapelStation

ShoreditchHigh Street

Station

GE19BRIDGE

Precast concretebox enclosure

Air rights - Precast concretebox enclosureprotects the linefrom future developmentworks

GreatEasternmain line

NorthLondonline

SHOREDITCHHIGH STREETBRIDGE

BISHOPSGATEVIADUCT

Bishopsgate Goods Yard

THAMES TUNNEL

DalstonJunction

Jubilee line

DLR

HammersmithCity line

District line

HaggerstonStation

HoxtonStation

of steel

SHOREDITCH HIGHSTREET BRIDGEBow arch bridge

HOLYWELL VIADUCTlinks up with the refurbishedKingsland viaduct

DALSTON STATION PODIUMA massive and complexstructure designed to support multi-storey development andaccommodate Cross-rail tunnels

SHOREDITCH HIGHSTREET STATION

SHOREDITCHSTATION BOXENCLOSURE- DETAIL

SLAB TRACK

BISHOPSGATEVIADUCT

GE19 BRIDGESteel, Warren truss bridge

BISHOPSGATEGOODS YARDPrime develop-ment area300t

above ground10m

foundation piles1,366

viaduct length span400m

platform length100m 84m

ShadwellStation

WappingStation

RIVERTHAMES

SHADWELLBASIN

CANADAWATER

GREENLANDDOCK

RotherhitheStation

Surrey QuaysStation

New CrossStation

New Cross GateStation

Canada WaterStation

REGENTS CANAL

Central section Southern extensioncentral sectionNorthern extension

HOLYWELLVIADUCT

Kingsland Viaduct,refurbished masonryarches and additionof underbridges

On embankment

1/4 mile

Victorian road bridge replacement


Concretetrough takesslab track

Concrete sleeper

Mass concrete slab

Boot(absorbentmembrane)

Rail mountedon sleeper

Mass concrete slab

Rails mounted onconcrete blocksleepers

Track sections- lengths tosuit project

Network Railmain lines

Steel, Warrentruss bridge

Concrete ramp

Concreteramp

75m32m

10m

Surrey CanalRoad bridge

NEW CROSS GATEFLYOVER

THAMES TUNNEL REFURBISHMENTThe East London line has its roots in the Brunel’s construction beneath the Thames (c. 1825 and 1843). The tunnel was refurbished for waterproofing and to take slab track.


NEW CROSS GATEDEPOT

To avoid the need for points a much larger grade crossing was required over the existing, near capacity, Network Rail main lines. A 1200t Warren truss bridge with a 75m span was employed

WAPPINGSTATIONVENTTo create a second means of escape for the station, shafts were sunk either side of a Victorian, brick lined, smoke ventpile depth

30m

span75m

of steel1200t

shaft depth16m

21 -23mspans,34m atstationentrance

Pile cap

10m

Precastpanels

Precastdeck

Portal framesections

To Croydon

Extension forcompletion 2012

To ClaphamJunction

graphic: © www.paulweston.infographic: © www.paulweston.info

Cast ironstruts

Masonry Vent

Escape shafts

Made ground

Drift

London clay/thin layerLambeth group

Thanet sandsMass concrete

New openingNew opening

Used on the new viaducts and in tunnel sections, track slab improves stability, noise suppression and maintenance intervals

BOOTED SLEEPER - SECTIONFor areas requiring the most noise suppression sleepers are mounted in an absorbent membrane

21 - 23mspans

22m

6m

AIR RIGHTS DEVELOPMENT

Station

Crossrailtunnels

Podium slab

HOXTON SQ N1HOXTON SQ N1HOXTON SQ N1

BRUNEL RD SE16BRUNEL RD SE16

WHITECHAPEL RD E1WHITECHAPEL RD E1

MILE END ROAD E1MILE END ROAD E1

WAPPING HIGH STREET E1WWAPPING HIGH STREET E1W

ROTHERHITHE NEW RD SE16ROTHERHITHE NEW RD SE16

DALSTON LANE E8DALSTON LANE E8

NEW CROSS ROAD SE14NEW CROSS ROAD SE14

OLD KENT ROAD SE1OLD KENT ROAD SE1

LOWER RD SE16LOWER RD SE16

COPE ST SE16COPE ST SE16

KINGSLAND ROAD E2KINGSLAND ROAD E2

Skyway to the north

DaLStonJUnCtIon

“One section of beam has over 100 H40 bars at the top and bottom of the downstand beam and multiple links” Guy Anstiss, BBCJV

Complete: A new train zips into Shoreditch High Street Station

EAST LONDON LINE ExTENSIONMAJOR PROJECT REPORT

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heaD

The northern section of the London Overground East London Line, running mostly on once

abandoned Victorian viaduct, has to make a swing eastwards as it reaches the edge of the City of London. This enables it to link up with the old London Underground East London Line route to south London. Two major bridges, substantial new viaducts, reshaped cuttings and a new, relocated station at Shoreditch High Street, are just some of the works needed to make the link.

The new section takes the line through and across Shoreditch High Street, and on into the historic Bishopsgate Goods Yard area, once one of the industrial wonders of Victorian London. After three decades

of near dereliction, what was once a huge, two-level railway unloading depot with a half kilometre length of vaulted brick arches supporting its rail tracks has become the largest potential development zone in London and is ripe for major office and residential schemes.

Early work for the BBCJV meant clearing thousands of tonnes of brick rubble from the northern half of the nearly 5ha site. This was the residue of pre-contract demolition works which took away many of the old arches. Some remain, including the famous and now listed Braithwaite brick arches, built by Victorian civil engineer John Braithwaite in the 1830s.

“We established a truck route out of the yard using a tempo-rary Bailey bridge,” says Andy Swift, BBCJV project manager for the northern section civils works. The temporary bridge took construction traffic over famous Brick Lane, known for

its curry restaurants. The trucks then passed over a still intact Network Rail bridge, known as GE19, whose later demolition by Murphy and replacement by BBCJV was one of the largest jobs in this section. It crosses a six track wide cutting for the main lines between Liverpool Street Station for the East Coast.

Just beyond this bridge the line dips into cutting and then underground at the Valence Road portal. The brick rubble the trucks carried was used

otherStrUCtUreS

spanned the line of the tunnel, carrying the building loads into the ground. But there was concern about differential settlement between this section of foundation and the rest of the site, which was piled, so an alternative, piled, solution was developed.

Two rows of bored piles have been sunk on each side of the tunnel line, topped with pile caps that support walls carrying the podium slab, the station concourse and the multi-storey development above.

“This acts as a ground level bridge, one of the biggest on the job, so they can put the Crossrail tunnel in much later without too much settlement,” says Anstiss.

It sounds straightforward, but each of the 40 piles in these four rows measures between 1.8m and 2.1m in diameter, and has been bored to a depth of 40m – only just above the chalk layer that underlies the London clay. The reinforcement cages alone

weighed up to 13t, and required two splices to enable them to be lowered into the pile bore.

An inventive piling solution was also needed as part of the remedial work to the Forest Road bridge, which spans the rail cutting at the southern edge of the podium slab.

In the original design, all of this post-tensioned concrete structure was due to be demol-ished and replaced by a new bridge with no parapet on one side, to allow buses to come off the Kingsland Road and into a new bus station being built on the podium slab. However, the BBCJV felt that full demolition would be a complex process, as the structure is full of services that would have had to be diverted at great cost. It was also very close to neighbouring properties that would be affected by noise and vibration during the demolition.

Instead BBCJV proposed that the structure be retained, and

turned into a “hybrid”, with the post-tensioning remaining in place on the eastern half, while the parapet on the western side was demolished to allow the buses to turn off, with this half of the bridge supported by one of the walls designed to take the podium slab loads. The new pier wall is topped by an I-beam that is tied into the existing bridge reinforcement.

Beneath the wall is a large pile cap and a total of 66 piles, each

300mm in diameter. “We wanted 750mm diameter piles, but when we decided to keep the bridge, the question was: ‘how do we get the rigs in?’” says Anstiss.

Rigs large enough to sink 750mm diameter piles to the depth required would not have fitted under the bridge structure, so the design was changed to 450mm diameter piles instead. “That would have worked, but we had a problem with ground conditions,” says Anstiss. “It looked OK from the boreholes, but when we started piling, water started boiling up from the base. It meant that 450mm diameter wouldn’t really work because there wasn’t a rig available to allow us to manage the boiling sand.”

Instead, the design had to be changed again for 300mm diameter piles, with construction carried out in a sequence that saw a series of casings driven, with the piles augered out inside them. “We had to introduce

“We wanted 750mm diameter piles, but when we decided to keep the bridge, the question was ‘how do we get the rigs in?’” Guy Anstiss, BBCJV

“We established a truck route out of the Bishopsgate Goods Yard using a Bailey bridge” Andy Swift, BBCJV

The new station at Hoxton is built inside an existing set of rail arches, with the concourse constructed by punching through the brick piers.

To create this space, ground engineering specialist Bachy first installed low headroom mini-piles either side of each existing pier, and a ground beam was cast on top. Holes were then drilled through the brickwork, and needle beams threaded through the top of the pier, and jacked off the ground beam to support the arch roof while the material below was removed to form the required space.

New columns and a lintel beam were then grouted in place to form a portal frame within the pier,

and the jacks removed to allow the brickwork to sit back down on top of the frame. The BBCJV’s engineer Scott Wilson had to carry out considerable finite element analysis to ensure the new design could carry loads from the tracks above. For Haggerstone Station, the old viaduct was demolished and a new station built.

HOXTON AND HAGGERSTON STATIONS

bentonite before we hit the sand, and then keep excavating through the bentonite,” says Anstiss. “Then we had to grout under pressure to replace the bentonite, and at the same time install the 18m long reinforce-ment cages.”

Now that Dalston Junction station is complete, much of the massive civil engineering work will go unnoticed by passengers, but during construction it was one of the most complex parts of the entire scheme.

At maximum there were 306 operatives working on this part of the site, and the major plant used to construct it included a 64m concrete pump – the biggest available in the UK at the time.

With construction starting on the apartments that will sit on top of the podium slab and passengers starting to use the bright, airy, stainless steel lined concourse, this ultra modern station will soon be a centre point of modern Dalston.

Crossrail crossing: Piling at Dalston included working around the Crossrail route

Tight spot: Hoxton station was snugly fitted under Kingsland viaduct

Catalyst: The station at Dalston Junction is expected to trigger regeneration

Transfer beam: Massive steel beams will carry properry developments above Dalston Station




to infill part of that cutting, reshaping the gradient and approach to the new GE19 bridge. It also helped fill another part of the cutting which continued on the Bishopsgate side, swinging around towards Liverpool Street station. This was where the original Shoreditch Station was sited.

The new Shoreditch station is set in the length of the old goods yard, along much of a new viaduct which carries the track through the yard space and out across Brick Lane. This Bishopsgate viaduct carries the line on 400m of a new concrete elevated way, some 10m or so above ground.

The viaduct comprises pairs of mainly 6m high columns which are mainly circular or elliptical in cross section. They carry a large 3.5m deep edge beam on either side. “In fact the depth varies at centre span giving them a slightly arched shape” says Swift.

The beams form the platforms

and are connected by a concrete slab which forms the deep trackwork trough between them. Spans between are 21m to 23m long apart from an extra long 34m span across the street at the station entrance.

Concreting for these beams was reasonably complicated since they required a mass of heavy T40 bar reinforcement, up to five layers thick, which meant care was needed in placing the

concrete. “We used limpet vibra-tors on the formwork which gave us issues of noise and vibration to manage, since this is a busy area with a lot of residential property around,” says Swift.

Clusters of five bored piles support each end of a series of single pile caps as wide as the viaduct on which sit each pair of the columns that support the viaduct above. One cluster was bored very close to London Underground Central Line tunnels and monitoring equip-ment was set up to give early warning of possible distress.Fortunately there was none.

Piles are as much as 30m deep under the station section and around 22m deep elsewhere. They were driven into London clay on which much of the site rests.

“The clay rises from the Brick Lane end somewhat as you approach Shoreditch,” says Swift. There is terraced gravel beneath and for the longer piles that meant using a “wet

pile” system to bore them, with polymer support, into water saturated gravel.

Piles were “substantial” says Swift, between 1,200mm and 1,500mm diameter.

The larger diameter was used to achieve a shorter pile in a few places, allowing the pile end to remain in clay and avoiding the need for the polymer. Bachey Soletanche was subcontractor for the piling.

The longer piles carry the heavier loads in the central part of the viaduct where the 200m length of the new Shoreditch station is located. The entire station at rail level is enclosed in a precast concrete box, creating a kind of “tunnel in the air”. The box tube comes in two widths, a central portion enclosing the 100m long platforms and two smaller parts extending the station enclosure at either end; there is an option for future expansion of the platform lengths into these.

The point of the enclosure is

primarily to safeguard the line from future construction and development planned for the entire Bishopsgate area, with over-site “air rights” construc-tion around the station, possibly including a 40 storey high rise office development. Work is imminent, although delayed temporarily by the economic situation.

“The station enclosure is really an expensive, perma-nent crash deck to keep trains running while work is done later by the developer,” says Swift.

It is built from precast portal frame sections attached to the viaduct at 7.5m intervals. Three 2m high panels are bolted to each side of these before an insitu top deck is formed and poured.

There were challenges on the longer GE19 bridge to the east of the station site. This was fabricated and assembled by Fairfield Mabey. The assembly of the Warren truss bridge which carries the new railway on a

85m span over the six Liverpool Street main lines, went well. It was fully assembled on tempo-rary falsework on the track alignment in the space which became the approach ramp, and push launched into place.

“It was powered over using a multi-axle transporter provided by Abnormal Load Equip-ment” says Swift. A 30m long nose section was added for the launching at the front end and the ALE transporter sat at the rear end. “It was a balancing exercise to keep the nose up” says Swift “so we concreted the back end deck and added more weight, leaving the front deck to be done later. The launching was done with the strand jacks between the permanent concrete abutments being used as the launch fulcrum, and the ALE transporter at the rear end.”

West of Shoreditch Station, the line crosses Shoreditch High Street on a 35M span bowstring arch bridge fabricated by Fairfield Mabey partly within

the Bishopsgate Goodsyard site. There, the firm welded the curving steel beams to form the bow and set the vertical hangers.

A critical part of the job was a major crane lift for the completed 330t bowstring arch bridge, using the 1,200t Sarens crane on a May weekend in 2008. “The lift only took a couple of hours but 12 months of prepara-tion were needed beforehand” says Swift, not least because the busy crane is much sought after.

“We also had to coordinate

all the emergency services, local authorities, and others for a road closure,” Swift adds. The site needed proper preparation for the crane which arrived on some forty trucks and took several days to assemble. Ground had to be properly cleared, and an area piled to support the crane.

The viaduct continues west of Shoreditch High Street with the Holywell viaduct, curving sharply to take the line back across the street as it links north to the existing Victorian brick viaduct further on. Five 20m spans were needed, built close alongside a listed and untouch-able building on Shoreditch High Street, running within 330mm of it at one point.

This part of the work was preceded by significant archaeo-logical digging within the old Holywell Yard. The Museum of London was delighted by the discovery of the remains of an old monastery, including foot-ings and columns, various burial sites, plates and knives.

“The station enclosure is really a permanent crash deck to keep trains running while work is done later by the developer” Andy Swift, BBCJV

“The GE19 bridge was powered over using a multi-axle transporter. It was a balancing exercise to keep the nose up” Andy Swift, BBCJV

Shoreditch High Street: A 35m span bow arch bridge is lifted into place

GE19: The bridge was launched over six mainline railway tracks

New link: The line runs on a mixture of new and refurbished viaduct from Dalston to Shoreditch


EAST LONDON LINE: SOUTHERN SECTION


River ThamesWAPPING


ROTHERHITHE

HIGH WATERLOW WATER

Section

Masonryconstruction

River ThamesWAPPING


ROTHERHITHE

HIGH WATERLOW WATER

Section

Masonryconstruction

WhitechapelStation

ShoreditchHigh Street

Station

GE19BRIDGE

Precast concretebox enclosure

Air rights - Precast concretebox enclosureprotects the linefrom future developmentworks

GreatEasternmain line

NorthLondonline

SHOREDITCHHIGH STREETBRIDGE

BISHOPSGATEVIADUCT

Bishopsgate Goods Yard

THAMES TUNNEL

DalstonJunction

Jubilee line

DLR

HammersmithCity line

District line

HaggerstonStation

HoxtonStation

of steel

SHOREDITCH HIGHSTREET BRIDGEBow arch bridge

HOLYWELL VIADUCTlinks up with the refurbishedKingsland viaduct

DALSTON STATION PODIUMA massive and complexstructure designed to support multi-storey development andaccommodate Cross-rail tunnels

SHOREDITCH HIGHSTREET STATION

SHOREDITCHSTATION BOXENCLOSURE- DETAIL

SLAB TRACK

BISHOPSGATEVIADUCT

GE19 BRIDGESteel, Warren truss bridge

BISHOPSGATEGOODS YARDPrime develop-ment area300t

above ground10m

foundation piles1,366

viaduct length span400m

platform length100m 84m

ShadwellStation

WappingStation

RIVERTHAMES

SHADWELLBASIN

CANADAWATER

GREENLANDDOCK

RotherhitheStation

Surrey QuaysStation

New CrossStation

New Cross GateStation

Canada WaterStation

REGENTS CANAL

Central section Southern extensioncentral sectionNorthern extension

HOLYWELLVIADUCT

Kingsland Viaduct,refurbished masonryarches and additionof underbridges

On embankment

1/4 mile



Concretetrough takesslab track

Concrete sleeper

Mass concrete slab

Boot(absorbentmembrane)

Rail mountedon sleeper

Mass concrete slab

Rails mounted onconcrete blocksleepers

Track sections- lengths tosuit project

Network Railmain lines

Steel, Warrentruss bridge

Concrete ramp

Concreteramp

75m32m

10m

Surrey CanalRoad bridge


THAMES TUNNEL REFURBISHMENTThe East London line has its roots in the Brunel’s construction beneath the Thames (c. 1825 and 1843). The tunnel was refurbished for waterproofing and to take slab track.


NEW CROSS GATEDEPOT

To avoid the need for points a much larger grade crossing was required over the existing, near capacity, Network Rail main lines. A 1200t Warren truss bridge with a 75m span was employed

WAPPINGSTATIONVENTTo create a second means of escape for the station, shafts were sunk either side of a Victorian, brick lined, smoke ventpile depth

30m

span75m

of steel1200t

shaft depth16m

21 -23mspans,34m atstationentrance

Pile cap

10m

Precastpanels

Precastdeck

Portal framesections

To Croydon

Extension forcompletion 2012

To ClaphamJunction

graphic: © www.paulweston.infographic: © www.paulweston.info

Cast ironstruts

Masonry Vent

Escape shafts

Made ground

Drift

London clay/thin layerLambeth group

Thanet sandsMass concrete

New openingNew opening

Used on the new viaducts and in tunnel sections, track slab improves stability, noise suppression and maintenance intervals

BOOTED SLEEPER - SECTIONFor areas requiring the most noise suppression sleepers are mounted in an absorbent membrane

21 - 23mspans

22m

6m

AIR RIGHTS DEVELOPMENT

Station

Crossrailtunnels

Podium slab

HOXTON SQ N1HOXTON SQ N1HOXTON SQ N1

BRUNEL RD SE16BRUNEL RD SE16

WHITECHAPEL RD E1WHITECHAPEL RD E1

MILE END ROAD E1MILE END ROAD E1

WAPPING HIGH STREET E1WWAPPING HIGH STREET E1W

ROTHERHITHE NEW RD SE16ROTHERHITHE NEW RD SE16

DALSTON LANE E8DALSTON LANE E8

NEW CROSS ROAD SE14NEW CROSS ROAD SE14

OLD KENT ROAD SE1OLD KENT ROAD SE1

LOWER RD SE16LOWER RD SE16

COPE ST SE16COPE ST SE16

KINGSLAND ROAD E2KINGSLAND ROAD E2

The biggest civil engi-neering challenges were at Whitechapel and Wapping as part of the

need to provide all the under-ground stations with secondary means of escape (SMEs)

WhitechapelAt Whitechapel, a relatively simple steel truss bridge sufficed for the SME, with lattice towers on the platforms and steel stair-cases to link to an emergency street level exit.

But on either side of Whitechapel Station two large excavations will be required for the planned Crossrail station which will sit above the Crossrail tunnels but below the ELL. The two subterranean Crossrail concourses will be linked by a pedestrian underpass beneath the ELL tracks, and it made sense

to build the under rail structural elements during the ELL works. The ELL team also found itself involved in some other advance works for the Crossrail team.

Crossrail has almost no space in the streets above Whitechapel for work platforms from which to construct its excavations. To find space it has prepared for a major bridging structure to be built over a 70m length of the Whitechapel cutting.

This “crash deck” work plat-form will need to support major equipment and heavy plant and demands correspondingly hefty foundations, explains BBCJV engineering manager for central and southern sections Andy Bradshaw. During its work, the ELL team installed for Crossrail two rows of 600mm diameter piles on each side of the ELL tracks, with some careful design required to give pile lengths which stopped short of the Crossrail track tunnels. “The pile depths were limited to 10m,” Bradshaw says.

In order for the Crossrail crash deck piles to be installed BBCJV had to remove the old ELL service platforms at the base of the 10m high Victorian brick buttress-and-coffer retaining walls that make up the ELL Whitechapel cutting. This was a tricky job because the toes of the retaining walls had to be braced off each other throughout the works.

To prevent movement of the walls, work had to be done in two phases. In each phase, the existing platform was broken out in bays 4m to 9m long, new precast struts were laid across the trackbed and then a pilecap was constructed at each side of the cutting.

“We used hefty 406mm diam-eter tubular steel struts as tempo-rary support until the piles were cast,” says Bradshaw. “The struts were later reused for excava-tion support elsewhere on the project.” Circular voids had to be left in the pilecaps for later sinking of the piles needed to support the Crossrail work plat-form.

Two contiguous piled walls some 3.5m apart across the tracks were also cast to form the walls of the future Crossrail station connecting passage. A thick-ened section of the track bed makes a roof slab for this pedes-trian tunnel which will be exca-vated, when needed by Crossrail, without disrupting the ELL.

The cost of “several millions” has been met by the Crossrail project.

WappingAt Wapping station the main entrance uses the Brunel tunnel shaft to accommodate two lifts and a spiral staircase but at the other end there was no obvious second escape route.

“There was a brick lined smoke shaft however, about 11m across” says Bradshaw. It dates from the days when steam trains ran underground which they did until early in the 20th century. Either side of this 16m deep vent, it was decided to sink shafts in which steel staircases could be built, linked to the platforms by cross passages at the base that were created by breaking through the thinner infills between the retaining wall buttresses.

The original plan to form a rectangular box shaft with big 1100mm secant piles did not work within the overall construc-tion programme. A value engi-

“We used big 530mm diameter tubular steel struts as temporary support during the casting” Andy Bradshaw, BBCJV

Negotiating exisiting tunnels, contracts and Victorian structures was all in a day’s work for the East London Line team as it worked to construct and renovate the railway. This section of the project also involved work to ensure the new structures did not interfere with planned works for the Crossrail line which crosses the route. Adrian Greeman reports.

TUNNELS& TRACKS

HEAdiNg SoUTH

Wapping: Here, the line runs south into Brunel’s twin bore Thames Tunnel





Once the ELL emerges from its tunnels just past Surrey Quays onto conventional bal-

lasted track, it might be thought there was less to do.

But renewing bridges, providing for new connections to the mainline and future London Overground extensions and installing big flyover at New Cross were all significant chal-lenges.

And there was the building of a brand new carriage servicing depot to add into the mix.

Cope Street Bridge Two significant bridges carry busy South London road connections across the line just after Surrey Quays station, where it is still in cutting, rising out of the river tunnel section to surface running. Both of these were old Victorian bridges, 10m wide, comprising parallel cast iron I-beams and masonry jack arch infills. Both carried a single

carriageway road and pedestrian pavement and were supported in the middle by a central pier. Originally rail tracks ran either side of the pier but now they only run on the western side.

The cast iron piers did not meet modern derailment resist-ance standards and had to go. At the Cope Street bridge, an initial scheme for a single unsupported span was dropped because the deck beams would have been too deep. Instead new concrete piers were installed but set back from the live track, creating one long and one short span.

Simple replacement of the deck above was complicated by the high concentration of services carried within the decks, most critically a fibre optic cable. Diverting it to a temporary bridge during the work would have been very expensive – around £250,000. “And diverting it back afterwards would have doubled that,” says Andy Bradshaw, BBCJV construction engineering manager for the section.

Costs were contained after a value engineering study devised a scheme that left the narrow

strip of bridge deck with the fibre optic cable intact while the rest was rebuilt with new precast concrete beams. “And then we only had to move the cable once onto the new part and finish the construction,” says Bradshaw.

Rotherhithe New Road BridgeAt the second bridge, Rother-hithe New Road Bridge, an even more expensive utility diversion was needed to handle several high voltage cables which served most of South London. These were embedded in a concrete block which had replaced one of the original jack arches between two I-beams.

Rather than a double move for the cables at an overall cost of £1.4M, and some risk of blacking out a big part of the conurbation, BBCJV devised a system to leave the block intact and rebuild the rest of the bridge around it.

The bridge was tackled in two halves in order to leave a carriageway open for busy traffic.

Most of one side was demol-ished first, leaving the power line slab in place supported on its portion of the pier. Once the new steel beams were installed,

two transverse I-beams were then attached underneath the new deck, to support the power line slab, on either side of its support pier.

With the power cable slab load transferred to these temporary hanging beams, the pier could be demolished. A third steel I-beam was then installed between the temporary ones, to be a perma-nent support, while the outer two were removed.

The new Rotherhithe bridge has one single span. It is longer than before but does not run the full length of the old bridge’s two spans. Instead the far abut-ment was built outwards on the disused side of the cutting. Rebuilding the bridge in this way produced a net saving to the client of around £1M, says Bradshaw.

Further south in the Silwood depot, there is to be an eventual connection to the South London Line. Points suffice to make the transition on the up-line into London, but the down-line trains will have to dip under the up line to travel west to Clapham Junction.

Secant piled walls were used

to form a new cutting taking the connecting track down and around, with a slab placed across the top of this cutting to carry the up-line. The new grade separated junction has been built to avoid service disruption in the future when the project to connect the East London Line to Clapham Junction gets under way.

Further south, a third road bridge was replaced, this time with the straightforward demoli-tion and lifting in of a new deck with a 1,000t crane. Apart from finding space between buried services to put crane outriggers, the main problem was to avoid

traffic closures on weekends when Millwall Football Club had home games, says Bradshaw.

New Cross Gate FlyoverA much bigger grade separated crossing was needed near the end of the renewed East London Line section where it merges with and uses the existing Network Rail slow lines at New Cross Gate on the route south to Croydon and Crystal Palace at New Cross Gate. New Cross Gate flyover avoids the need for a four-track ladder of switches and crossings to carry the ELL trains across four near-capacity main line tracks onto its own line which runs past the new service depot.

The connection takes north-bound trains heading for the ELL off the main slow line and then up an inclined concrete ramp to a 75m steel bridge which spans the four tracks. A short 32m steel span continues the 10m wide bridge from a concrete pier onto another inclined concrete ramp that carried the trains through the new depot and onto the ELL’s dedicated line.

The new ELL depot sits on old sidings which for some years had become a local authority site for impounded cars says Mark Walker of BBCJV who supervised the depot construction.

The depot is domnated by the four-track, four-crane, four train rolling stock maintenance facility and its three storeys of offices all housed in a huge 90m by 40m by 12m high rectangular steel-framed, steel-clad building. Inside the depot are three raised tracks enabling clear access below the trains. The fourth track is equipped with synchronized jacks capable of lifting a whole train in one minute for the purpose of bogie changing.

Another 90m building, split longitudinally into two, has one track dedicated to a twin-headed wheel lathe and a second in the other half committed to heavy cleaning and painting. It also has a blast and fire proofed top floor dedicated to an operational control and signaling centre which allows signallers 10 minutes to safey shut down all rail systems in the event of a fire.

NEW CROSS GATE DEPOT

neering rethink suggested sinking jacked caissons with mucking out by long reach exca-vator “which paid a health and safety dividend because you don’t need anyone in the shaft until you have reached forma-tion level and pumped out,” says Bradshaw.

This went well until the time came to make the first cross passage, excavating through what it had been thought would be firm London clay. Instead old rotten timbers, possibly some temporary works left in place by builders of the wall, were encoun-tered. These timbers posed a problem because, once disturbed, it was realised that they were providing a water flow route from the terrace gravels above. “And since the Thames is just next door the water was not going to stop,” says Bradshaw

Initial grouting was just washed out and a programme of minipiling between buttresses and shafts was devised to form a grout curtain to cut off the flow while the cross passage was completed. On the other shaft, forewarned, the grout curtain was created before any trapped ground water was disturbed.

Meanwhile inside the smoke vent a series of Victorian cast iron struts needed upgrading. Two levels of three rather elegantly shaped struts, with flared ends, had to be replaced. Architec-tural heritage considerations dictated that the replacement struts should resemble the origi-nals as far as possible. The upper struts were removed completely and new steel struts installed in their place, but the lower struts were more difficult because it was hard to see exactly how they connected at the wall.

Rather than risk displacing anything the lower struts were cut away in the centre and new steel sections were inserted. Around the remaining cast iron lengths a sleeve was devised in

SoUTH of THE THAmES

new steel to take the loads. Apart from the complexity of this work the job was a major exercise in logistics, with a crane at the top of the shaft juggling old and new pieces of steel around both the permanent struts and three sets of 250kN temporary props.

Marc and Isambard Brunel had accessed their Thames Tunnel works via a shaft on the south bank of the Thames.

To make a lasting contribu-tion to London’s engineering heritage, BBCJV cast a whole new floor in, sealing it off from the tunnel and trains, so leaving it available to the Brunel Museum to develop as additional exhibition space, including a chance for visitors to see the orig-inal shaft structure.

Other station work was also complex.

“After contract award the client decided to completely refur-bish the station buildings and platforms bringing them up to modern standards; this devel-oped into interior demolition back to bare walls and even some of those were reconstructed,” says BBCJV stations project manager Phil Wharton.

Renewing bridges, providing for connections to the mainline and future London Overground connections and a flyover at New Cross were big challenges

Excavation through what had been thought to be London Clay instead turned out to be rotten timbers, possibly from some long-forgotten wharf

Depot: The South London site is a huge 90m by 40m steel framed structure

Whitechapel: Vital interchange

Hot stuff: Thermal welders at work Junction: The depot is just to the east of the massive New Cross Gate flyover

Wapping station: Orange temporary struts brace the original 16m high buttress-and-coffer brick retaining walls while the original struts are replaced with new, stronger white lookalikes



The most complex part of the operation to build the four track crossing was placing the main 1,200t Warren truss for the 75m span. “Fortunately there was some unused Network Rail land alongside the mainline tracks where our subcontractor Fairfield Mabey could assemble the bridge,” says Bradshaw.

To get it into position needed a 56 hour possession, booked long in advance.

“We used multi-axle self-powered transporter units for the move. The truss was jacked at finished height onto trestles on the back of the transporter units and then moved south-wards some 60m. Then one end of the truss was slewed across in a 60m long arc while the south end took a shorter 20m long path” says Bradshaw.

The construction yard embankment area was previ-ously surfaced with a 300mm thick layer of recycled demoli-tion aggregate to improve its load bearing capacity for the move.

To prepare the four mainline tracks for the heavy loadings of the bridge and its transporter units, various bespoke level crossing options were consid-ered. But they would have been expensive, not only because a lot would have been needed but they would have had to be tailored to fit irregular track and sleeper spacings.

Instead, a simpler solution was found. By removing the third rails that provide traction power for trains in Network Rail’s Southern Region and protecting the running rails with steel channel sections, it was possible to build up a load bearing platform using conven-tional ballast. This meant it was unnecessary to keep the temporary fill and the existing line ballast separate. Any surplus would simply form part of the railway afterwards.

“To get the flyover into position needed a 56 hour possession. We used multi-axle self powered transporter units for the move” Andy Bradshaw, BBCJV

On the new viaducts and in the tunnel, the East London Line sees the first application of the Sonneville boot system of slab track.

For new viaducts and tunnels, slab track was installed, using the Sonneville system of concrete blocks to support either end of the sleeper, all embedded in a concrete slab. Each independent block sits on a neoprene pad inside a rubber “boot” which dampens vibrations; and the blocks can be extracted and the boot renewed easily when necessary. Noise suppression was the key factor on viaducts particulary as they run through crowded areas of the city, but reduced maintenance was the prime reason for the choice in the tunnels, where only night-time access is possible.

“We had two variants of slab, the basic one and in some places the mass spring system,” says BBCJV’s Steve Bradley who was

track construction manager for three years of the project. The difference lies in the concrete surround for the blocks. Mostly this is just mass concrete poured around the booted blocks that are carefully positioned by hanging them from the precisely positioned rails that have been placed inside a basic concrete trough. But for additional noise suppression on viaducts, the trough is lined with an additional absorbent membrane and the

concrete track slab poured around it has to be reinforced to handle the additional movement created by the addition of the membrane.

The boot system is complex to install, since each sleeper end is independent and must be accurate for rail inclination, gradient, gauge, alignment and more, before fixing in concrete. It is the first application in the UK. Drivers have already informally declared the line the smoothest they have experienced.

TRACK

Big move: Four multi-axle transporters move the 1,200t Warren truss for the New Cross Gate flyover into position

Covering up: Temporary fill cover the track during the flyover move

Sound solution: Rubber “boots” under the track damp down vibration

Truss: Last minute adjustments

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