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Issue 101 – March 2013

Sorting out Shugborough

An unexpected inclusion in Network Rail’s work programme for Christmas 2012 was the relaying of both lines through Shugborough Tunnel.

The tunnel, 777 yards long and dating back to 1846, lies on the West Coast Main Line just north of Colwich Junction, south of Stafford. It is on the Shugborough estate of the Earls of

Lichfield, the site is of special scientific interest, and its portals are both Grade 2 listed.

The project’s late inclusion in the Christmas programme stemmed from the imposition of a temporary speed restriction (TSR) through the tunnel in 2011. This was caused by the restricted clearances in the tunnel resulting from years of track maintenance works lifting the tracks. The speed restriction on this critical section of the West Coast route could not be tolerated for any length of time. In consequence it was decided that the renewal and lowering of the tracks through the tunnel should be added to the work programme for Christmas 2012, even though this challenged the normal planning timescales.

Once the project was added to their workload as a ‘reactive renewal’ in March 2012, Network Rail’s project manager Patrick Vallely and his colleagues were compelled to enter into negotiations with the train operators concerned, particularly Virgin Trains, in order to agree the necessary possessions. This was quite a task in itself as normally Patrick and his colleagues work on a rolling three year work bank. This project was to be planned and delivered in roughly half that time.IMG-20121227-00044 [online]

After discussions with all concerned, Adrian (Ade) Brookes concluded an agreement which granted Network Rail a possession of both lines for a period of eight and a half days between 21:00 on 24 December 2012 and 07:00 on 2 January 2013.

Planning for success

What was eventually to become a £2.5 million project required very careful advanced planning by Patrick and his Network Rail colleagues, including Paul Eamonson (scheme project manager) and Ian Marks (construction manager). They worked in alliance with other company people and colleagues from suppliers. A critical issue, recognised early on, was the importance of having the necessary engineering trains, and the haulage for them, during the Christmas period. It became clear that this haulage would not be available unless some special arrangements were made, and in the end Network Rail had to cancel some less critical works elsewhere to free up the resources required.

At first, few details of the structure of the tunnel or of the existing track construction were available to the project team, and without this information it was difficult to develop a plan or specification for the works. Detailed desktop structural investigations were undertaken along with surveys to confirm the arrangements of track and drainage within the tunnel.

Many historic drawings were located but, as with many projects of this era, these were largely aspirational rather than as-built.

One mystery surrounded the tunnel ventilation shafts. It was known that the tunnel had been constructed with nine of these but, at some past time, they had been sealed and their locations were no longer known. The details of other relevant infrastructure, particularly cable routes and overhead line equipment, were also needed and were obtained similarly by desk study and/or site survey.

It was established that the OLE was on the limits of its adjustment and that the drainage was not functioning correctly. Moreover, it was clear that the cable routes, one in each cess, were going to be in the way of the track and drainage works and additionally there were hard materials below ground which were sometimes too high for the necessary depth of excavation for the new track and drainage.

With excavation depths of around one metre there was the possibility that the stability of the tunnel structure could be put at risk by the work – but the depth could not be reduced because of the need to lower the tracks to restore the clearances to normal standards, one of the key project objectives. As a result, Network Rail’s structures team, along with consulting engineers Donaldson Associates, assessed the safety of the tunnel structure in relation to the proposed works and advised on what should be done.

All of these issues had to be accounted for in the plans for the works. It was decided that during the main possession the OLE should be released from its supports sufficiently to permit tying it back out of the way of the track relaying machines (TRMs) to be used for the track works. The cable routes also needed to be moved clear, and it was agreed that this would be done by diverting the cables to new routes hung on the tunnel walls. If all this was not enough, the drain in the six foot required complete renewal and the drainage outfall some way outside was found to be obstructed and in poor condition.

shug4 [online]Attention to detail

It was quickly established that significant enabling works would be needed prior to the main possession, and so a number of smaller track occupations were used in the preceding six months. The drainage outfall was cleared and repaired, the cable route diversions were completed and a number of other preparatory tasks were got out of the way.

The advice of the structures experts was that the excavations could not be carried out all at once, and that there should be a real time monitoring system in place to watch for any movements in the structure throughout the works. The track and drainage excavations were therefore planned to be staged accordingly.

Datum Monitoring, specialists in the monitoring of structural movements, were engaged to design, install and implement the tunnel monitoring system which they installed using a high accuracy laser distometer and targets fixed on the walls at 10-metre intervals throughout the tunnel.

This system was manned and monitored throughout the excavation works, but thankfully no movements of the structure were observed.

OLE contractor for the main possession was Bourne Rail, who undertook the work of tying the overhead wires out of the way of the track renewal and reinstated it to the new design afterwards.

Main contractor for the works was Amey Colas, who used contingent labour from various suppliers including SkyBlue. Network Rail encouraged an ‘alliance’ approach to the project, so Amey Colas’ permanent way engineer Tom Dwyer and construction manager Tim D’Arcy were heavily involved in planning the successful outcome of the job. It was critical to ensure that the morale and motivation of staff on the site was maintained at all times during the possession. People working in a tunnel far from their families and friends through Christmas might well be demotivated. A good deal of thought and effort was therefore given to ways in which this problem might be alleviated. The phasing of the work shifts was planned with special care, for example.

During the main possession the drainage renewal was undertaken in a rather unusual fashion. As the hard spots limiting easy excavation could not be removed in the time available, conventional catchpits could not be used in all the locations where they would normally have been. Instead, rodding eyes were used at locations where the level of the hard material obstructed the excavation for catchpits.

Track relaying machines (TRMs) were used to lift out the old track in panels, loading these onto an engineering train for removal from site. Though no longer good enough for further use in the WCML, the old panels are perfectly serviceable for use on lower category lines or sidings and will be reused accordingly. After excavation and removal of the old ballast, new ballast and new track were installed.

Once the first line was completed and ‘fettled’ to a suitable standard, everything was swapped over to allow the other line to be renewed in the same fashion. The track was tamped in preparation for the reopening of the line.

Keeping things fresh

The tunnel was regarded as a confined space and so forced ventilation was needed. This was provided by specialist contractor Factair which provided six of their modular 1220mm diameter fans to force air to flow through the tunnel and ensure 17 changes of air per hour inside the structure. The air current reached speeds up to 2.7m/s. This may sound like overkill, but the specialist contractor points out that the tunnel has an air volume of almost 33,000 cubic metres, and that this volume of air weighs in the region of 39 tonnes at normal pressure and temperature. The fans were placed in the cess adjacent to a tunnel portal, clear of the line, permitting unrestricted use of both tracks. Factair staff attended to the equipment throughout the possession.

Factair also supplied air-fed respiratory protection for staff involved in particularly dusty operations such as ballast tipping. The kits supplied for this are sophisticated incorporating hard hats and both eye and ear protection in the one system.

Finally, Factair provided an air quality monitoring service during the works. Staff were on duty throughout, monitoring oxygen levels and checking for toxic and pollutant gases including carbon monoxide. They also recorded temperatures, air speeds, dust concentration and more, taking over 3,000 readings in all. Their reports provided their client with evidence that the appropriate duty of care had been exercised in respect of their staff, sub-contractors and others who might be affected.

Some 7,200 tonnes of new ballast, 2,300 new sleepers and 3,304 metres of new rail were used in the project, together with 840 tonnes of pea gravel and 660 tonnes of sand and the renewal of 1000 metres of drainage. A total of 1,800 yards of track were relaid, 850 on one line and 950 on the other.

The project’s critical path was closely monitored by the project team throughout the possession and corrective action was taken immediately when necessary to keep the works on time. Network Rail had an operations delivery manager (ODM) on site throughout to assist when there were any railway operational issues, and this proved to be a valuable contributor to the successful achievement of the work and the handback of the possession nearly two hours early on Wednesday 2 January.

An additional challenge for Patrick and his colleagues was a planned visit by the Secretary of State for Transport, the Right Honourable Patrick McLoughlin, accompanied by Network Rail’s CEO Sir David Higgins and track programme director Steve Featherstone. This too went well and the visitors were apparently suitably impressed.

The TSR has now been removed as the clearances have been restored to the norms required for the route. The new track and drainage will ensure better track quality, now and for the foreseeable future, with a reduced maintenance requirement and greater reliability.

Shugborough is well and truly sorted.

A tale of two platform extensions

On the face of it the two platform extensions should have been very similar – the same busy rail line out of Paddington Station with the same 125mph line speed, approximately the same length and width of extension, the platforms being extended at the same side of the station, the sites just a few miles apart and so the same trains passing through the worksite.

Even the same access point was used for some of the work. However, the solutions required from Tata Steel Projects to be able to deliver the platform extensions at West Drayton and Langley Stations required very different solutions.

The two projects formed part of the enabling works package for Crossrail West Outer Stations and followed on from the successful completion of a platform extension at Hayes & Harlington Station. Acting as principal contractor, Tata Steel Projects used its niche Modular Platform systems to be able to deliver both projects in different but equally challenging environments.

West Drayton

The extension at West Drayton was located on the top of a Victorian earth embankment with a raised ground profile due to a previous platform structure and with numerous buried services. Furthermore, there were residential properties immediately on the toe of the heavily vegetated embankment and so access was limited via the station access or a temporary scaffold.

It therefore became clear that a solution requiring minimal depth of construction, minimal excavation and removal of spoil and also minimal wet works was required. Fortunately, Tata Steel Projects can supply lightweight modular platform systems (previously known as the Corus Rail Modular Platform Systems) that can be constructed without the need for High Wycombe _11-03-31 012 [online]mechanical lifting and only requires a gang of installers.

This patented system, which is a Network Rail standard design and which has been used on over 80 new platforms and platform extension projects on the UK and European Rail networks, is unrivalled in its constructability in difficult access conditions and has enabled the delivery of projects to some extremely challenging timescales.

However, the frequent leg centres of the standard system still require a foundation and though this is typically easy to build, as the dead loads can be 60% less than equivalent concrete systems and the location of the footings can be behind the blue fencing and out of the track support zone, it still requires a simple strip footing or raft.

“At West Drayton we calculated the cubic metres of spoil removal, the amount of concrete that would have needed importing and when we also considered the narrow space between existing structures and services that was available to place the foundations we came to the conclusion that this solution was not ideal,” commented Tata Steel Projects’ Business Manager, John Wood.

Long Span

Several years previously, Tata Steel Projects had developed the ‘Long Span’ platform system which had been used in parts of other schemes, and it was decided that this variant was the best option.

The ‘Long Span’ system uses the same basic premise of the standard modular platform system, as it shares many components and so has the same flexibility and future adjustability inherently designed into it, but replaces the frequent legs with a spanning ladder beam that bridges the 7.32 metre gap between pairs of piles, although other spans can be developed.

At West Drayton the construction depth available above existing critical services was constrained to such an extent that the Ladder Beam had to re-engineered.

The proximity of residents and the difficulty with spoil removal meant that Tata Steel Projects used low displacement piling for the foundations on this scheme. However; unseen obstructions in the ground caused some difficulty with this operation.

The nearest access point was also found to be unsuitable as the hardstanding was insufficient to crane ‘Long Span’ platform units onto road rail trailers. However, all twelve units of the ‘Long Span’ platform system were able to be delivered to an access point five miles from West Drayton, taken to the worksite by road rail vehicle, and the main bulk of the platform structure installed during a single shift of a weekend blockade.

Hayes and Harlington IMG_0686 [online]Tata Steel Projects’ installers were then able to follow behind and adjust the platform system to the theoretical gauge, install rear fencing, platform lighting, signage, cess stairs and surfacing (using a thin GRP overlay system which was easy to transport to site) during traffic hours and non-disruptive possessions.

Langley

In theory, the extension at Langley Station was much simpler to construct with the possibility of creating a temporary access point adjacent to the footprint of the platform extension.

Therefore the method chosen was more typical of the Tata Steel Projects platform system. This uses a series of components that can be installed without the need for mechanical lifting. The bulk of the installation can take place behind blue safety fencing so the result is an equally rapid construction, just with a different method of working.

The foundations were also much simpler, though piling was used around the existing track drainage system. Also it was possible to deliver materials for a traditional asphalt, precast concrete coper and tactile paving surfacing.

Tata Steel Projects were also able to deliver a temporary lift to the opposite platform which was out of gauge.

Similar, yet different

So the two stations, while outwardly similar, required modular and offsite construction techniques from both ends of the spectrum, one lightweight with a high degree of repetition able to be installed manually and the other using much fewer but larger units transported and lifted into position with heavy equipment.

However, they did both have several aspects in common. The modular system allowed construction to be carried out safely by minimising hours worked on-site and to a high standard of quality by using factory quality assurance techniques for the components. The design is future-proofed by the inherent adjustability in the systems while the components are durable and meet the requirements set-out by Network Rail standards for steel platforms.

Also, the installations incorporate techniques that are inherently sustainable such as using offsite construction which minimises waste and transportation and also using steel which consists of a high degree of recycled material.

Importantly, by establishing the correct solution for the construction of each of these projects, and by working in collaboration with the client and key delivery partners, Tata Steel Projects was able to deliver both these schemes simultaneously.

There was actually one further similarity between the two projects. Both received a STAR Award from Crossrail in recognition of an excellent Health & Safety record and good site management. Teams of auditors visited both sites to conduct in depth assessments of the quality of both projects before presenting those awards. So they really were two jobs well done!

Keeping water out

Elsewhere in this issue, the consequences of having too much water on track or within embankments are discussed. However, water is also a problem for structures engineers. Water getting into bridge decks, or leaking down into tunnels, can cause major difficulties. Waterproofing therefore becomes an important consideration.

With over 30 years experience in the rail industry, Stirling Lloyd’s high performance waterproofing systems continue to play an important role in the protection of challenging rail projects in the UK and around the world. As some of its most recent projects confirm, tunnel and bridge deck waterproofing remains a critical consideration on any rail engineering programme.

Buenos Aires Metro

The growing popularity of sprayed waterproofing membranes for use in tunnels has again been highlighted on the Buenos Aires Metro, the mass transit system that serves the Argentinean capital.

The Buenos Aires metro, known locally as ‘el subte’, is an extensive underground system consisting of six lines. One of them, Line B has recently been extended to include additional stations and at the end of the line is a cavernous, four track wide parking garage for the metro trains. Excavated using the New Austrian Tunnelling Method (NATM), this huge space is 18 metres in diameter and 11 metres high and its tunnel lining comprises a cast in-situ invert section and an arch and crown upper half lined with sprayed concrete for both the primary and secondary linings. The tunnel sits 10-15 metres below the water table.

A second new structure, the workshop, which utilised a similar construction method, is approximately 12 metres wide and 6.4 metres high and lies around 20 metres below the water Blackfriars Bridge - View 2 IMG_0189 [online]table. With both spaces therefore significantly below the water table and the ground conditions in Buenos Aires very permeable, the requirement from the client, Sbase, was for a higher level of watertightness than had been achieved in previous projects.

The design of both structures incorporated lattice girders and temporary sprayed concrete as the ground support primary lining. Due to a short construction programme requiring a fast build speed, the design was for permanent unreinforced sprayed concrete as the secondary (final) lining from axis to crown and cast in place concrete in the invert. To facilitate the use of sprayed concrete as the secondary lining, Integritank HF seamless sprayed waterproofing was specified as this forms a strong bond to both the primary and secondary linings. Successfully spraying on to a sheet system is very difficult and so they are not commonly used where sprayed concrete secondary linings are used.

In common with all NATM constructed tunnels, the waterproofing membrane would not be accessible after the secondary lining was installed. In addition, due to the permeable ground and the location of the structures below the water table, the ground was to be de-watered locally. This meant that if a system was installed that contained defects they would not become apparent until after the secondary lining had been installed and the de-watering pumps switched off.

Consequently Benito Roggio, the main contractor, required a sprayed waterproofing membrane that could be tested in-situ after it had been installed but before the secondary lining was applied, to prove that a continuous, defect free waterproofing installation had been achieved.

The Integritank HF system has been specifically designed for incorporation between the primary and secondary concrete linings in NATM tunnels, as well as SEM (Sequential Excavation Method) and SCL (Spray Concrete Lined) types. To meet the challenge of the rapid build programme for both Metro caverns, the waterproofing was scheduled to be installed in phases. Traditional sheet waterproofing usually requires installation in one continuous process which can be restrictive to other works, particularly in a linear tunnel application as they wait for sections to cure.

Here, however, application could be discontinuous with the untreated areas between the coated areas being sprayed at a time more convenient to other trades.

In total 20,000m² of Integritank HF was successfully installed in the two caverns of Buenos Aires Metro Line B. Both the contractor’s requirement for rapid installation to meet a short programme and the client’s for a high degree of water tightness were met.

Blackfriars Bridge

Back in the UK, Stirling Lloyd’s bridge deck waterproofing systems have been used by VolkerLaser on the second phase of a £3 million refurbishment contract now nearing completion at London’s Blackfriars Bridge. The 125 year old landmark wrought iron bridge was refurbished as part of the Thameslink programme to give greater rail capacity through the centre of London.

The works, carried out in two phases, consisted of applying some 10,000m² of Eliminator spray waterproofing to the largely steel, with concrete elements, substrate and 1,000m² of Hytec sheet waterproofing to the end abutments.

VolkerLaser overlayed 4,000m² of the waterproofing with 900 tonnes of Laserphalt high modulus mastic asphalt, with the remaining area being covered in ballast. The company also installed 50 metres of bespoke expansion joints and applied 25,000 metres of Stirling Lloyd’s Metaset Flex Sealant to joint gaps in the deck plate.

Due to adverse weather conditions, VolkerLaser designed and erected bespoke tenting to cover the works and operated around the clock to ensure that each stage of the programme was completed on schedule and achieved the client’s key performance indicators. The scheme also provided another excellent rail bridge showcase for Stirling Lloyds’s waterproofing capability and, as Andrew Welsh, VolkerLaser’s associate director said: “Blackfriars Bridge is one of London’s most congested sites where rigid timescales and health, safety and Photo 3 - Spraying Membrane [online]environmental standards are of paramount importance.”

Londonderry to Coleraine rail track

In Northern Ireland, Londonderry’s status as the UK’s 2013 City of Culture has led to improvements in transport infrastructure to accommodate increased visitor numbers. This has included major engineering works on the main line between Londonderry and Coleraine with the track closed until April this year.

The work is the first phase of a £75 million upgrade to the track and represents a significant investment by Northern Ireland Railways. It includes a full relay of the track system between Coleraine and Castlerock and between Eglinton and Londonderry and it is on a number of bridges close to the Coleraine section that Stirling Lloyd’s approved bridge deck waterproofing systems have been used.

Four bridge structures have been treated in total. Two road-over-rail structures have seen the installation of Stirling Lloyd’s spray applied ‘tightly-bonded’ Eliminator system, with captive blasting of the concrete substrate used to prepare the deck ahead of the application of a coat of PAR1 Primer, membrane and Tack Coat No.2, the latter being used to enhance the strong bond between the membrane and the subsequent 120mm of surfacing. Two separate rail bridges have been waterproofed using Stirling Lloyd’s ‘loose-laid’ Hytec system, a flexible polypropylene sheet membrane offering exceptional mechanical properties. Hytec, designed especially for fast track rail possession where deck and climate conditions are uncertain, was the ideal choice for these Coleraine rail bridges.

These three examples show the variation of waterproofing challenges faced by structures engineers, and the lengths that they have to go to to keep water where it belongs – not on the railway.

Running free

There are good opportunities for those seeking virtue at Christmas-time. Donate to charity; attend midnight mass; force down a third Brussels sprout without grimacing. Or, if you are responsible for a 53 hour possession starting just when Santa should be doing the rounds, show your face on Christmas morning to see how your site team is getting on.

A high-level visit to the worksite at Horton Bridge on the Great Western main line in Hillingdon therefore felt cheated upon arrival at 9am to find no work in progress. However, the surprise was a pleasurable one, since the team were actually packing up having completed installation of a new footbridge in just 8 hours.

There was plenty of other work going on too. The visit continued to view the demolition of three other bridges, all in the same possession within five miles of each other. These bridge works were carried out by Network Rail on behalf of the Crossrail project, to enable installation of overhead line electrification on the Crossrail West Surface Works section between Paddington and Maidenhead.

Curtain-raiser

The Christmas works were just the first stage. At Easter, the works will reverse at the same sites with three installationsstockley_02 [online] and one demolition. And these bridge modifications, contracted to Hochtief, include parapet alterations at a further 12 bridges between Maidenhead and the junction to Heathrow Airport at Stockley flyover.

The project to electrify this section is being delivered by Network Rail. In addition to being enabling works for Crossrail, it will also form part of the Great Western main line electrification scheme. As technical coherency between the Great Western and Crossrail projects is necessary, this section uses the same overhead line equipment as the rest of the Great Western route.

These four bridges were reconstructed because they were all three-span bridges with curved arches which clashed with the required clearances for the new overhead lines.

The new bridge at Horton, which was built alongside the old, was commissioned prior to removal of the old bridge so allowing the diversion of services. For the other bridges constructed on similar alignments, it was necessary to remove the old before the new could be built.

Invisible bridges

Three bridges at Horton, Trenches and Old Stockley Road were required to carry pedestrians and cycles only. Designers Hyder working for Hochtief developed a single design for installation at all three locations, with a single span of 33 metres.

Geoff Hancox, designated project engineer for Crossrail, explains that the 5.6 metre clearance from rail to soffit is a key feature of the new footbridges. Hancox said: “This allows free-running of the OLE and so, for the electrification, it is almost as if the bridge is not there.” This clearance also allows for the auto-transformer feeder cables and will provide for the largest high-cube container traffic.

Hancox notes an increasing interest in whole life costs for electrification, including an ongoing baselining exercise being carried out by Network Rail. “If we can attribute OLE maintenance costs against individual bridges, we can gain a better understanding of costs associated with reduced clearances. This could assist with future decisions on track lowering compared with reconstruction. It may be that increased costs of reconstruction can be balanced against longer term savings from providing greater clearances for the overhead line equipment.”

The single spans also give flexibility for the track layout. Hancox continued: “We took this design decision with an eye on the future. But, it is already giving unexpected benefits and we are taking advantage of this flexibility. A new crossover is planned at the site of Old Stockley Road bridge, to give operational mitigation during the works at Stockley flyover.”

These will add extra ramps and overbridges, removing conflicts for Heathrow Express trains accessing the Up Relief line.

Ramped off

A downside to increasing the clearances at the bridges is the access from the surroundings. Especially where steep gradients were formerly provided, fitting compliant steps or ramps into the available land became a challenge.

New ramps will be provided to all the footbridges. At Horton, an elevated ramp structure will be tucked into the tight space between the railway and the Grand Union canal. At Old Stockley Road, back-spans to the footbridge will be provided allowing the approach embankment to be graded back to the railway rather than needing an abutment.

At Trenches an 80 metre long approach ramp will be provided, although even this required agreement with the local authority for the continuous ramp gradient of 1 in 12 with a single landing. The ramp gains a maximum height of some 2.5 metres over the adjacent land using Keystone reinforced earth units. The project team are currently looking at using lightweight aggregate to reduce surcharge on the existing embankment.

The fourth bridge at Middlegreen Road is the sole bridge still carrying a road, albeit a single lane with traffic light controls. It would have been prohibitively costly to modify the road approaches to provide the same clearance as the other bridges hence a clearance of 5.2 metres will be provided.

Due to the heavier road traffic and limited construction depth dictated by the approaches, a single span was also not viable. When it is reconstructed at Easter, the bridge will reuse the existing piers and abutments using precast concrete portal units to form a three-span structure. A temporary footbridge provides continuity of access for pedestrians until the new bridge is installed.

Horton Bridge_V2 [online]Eight-hour footbridge

The footbridges were designed for efficiency of erection. Jason Hamilton, project manager for Network Rail, explained: “One installation was carried out over Christmas at Horton. It was an extremely smooth operation. We have also realised economies of scale by replicating the same design at the other locations.”

The decks are of steel-concrete composite construction. Weathering steel was used for the main girders to minimise future maintenance requirements. The twin girders and bracing were provided and assembled at ground level by Mabey.

They were lifted as a complete 29 tonne unit by a 500 tonne crane provided by Ainscough.

The concrete deck was formed of 11 precast units each 3 metres long provided by Banghers Precast Concrete. The deck system was designed to be stable in the temporary configuration with the precast units craned into place and supported by the main girders. However, this system requires careful coordination of the pockets within the precast units, the reinforcement projecting into these pockets and the shear studs projecting from the main beams.

Hamilton says, “Hochtief carried out a trial lift of a precast unit the week before the possession. They mapped the precast unit onto the main beams to ensure the shear studs and reinforcement lined up. During the possession, every unit sat right first time and this was a major factor in achieving the eight-hour installation time.”

In-situ concrete will be poured later to stitch the precast units to the main beams, giving the composite action necessary to carry live loads rather than just self-weight. Grout checks were installed prior to lifting the precast units so this work can be carried out in other, shorter possessions.

The precast units were lifted into place with parapet stanchions attached to provide edge protection from the outset. 1.8 metre high solid metal parapets are provided at all the footbridges. In addition, the team consulted the route crime records and attributed trespass incidents to each bridge. With 17 recorded incidents of objects thrown onto the line over the last 10 years, Horton Bridge will be fitted with an overcage to reduce vandalism. Since the same design is used for all the bridges, this could be added at the other bridges in future if required.

Bulldozing Brunel

Taking the metaphorical wrecking ball to Brunel’s original fabric is not something to be undertaken lightly. English Heritage carried out an extensive consultation on the whole Great Western route following the announcement of the electrification scheme. The consultation concluded in July 2012 with the listing of 35 further structures in addition to the 56 structures previously listed.

The four bridges removed by this project were identified for replacement in the Crossrail Act in 2008. This followed discussion and agreement with English Heritage about which structures could be reconstructed and which could have track lowering.

Typically for railway structures, various alterations had been carried out over the years. The first arch span was a semi-elliptical arch constructed in the late 1830s for Brunel’s broad gauge. The addition of the relief lines in the late 1870s led to a second span to standard gauge. A goods line was added in 1914, leading to the third span, built in a variety of forms including arches and flat metal spans.

Jason Hamilton commented: “Demolitions can be difficult. These structures were in excess of 100 years old, some sections approaching 175 years. No matter how much investigation you do, coring, records, trial holes, you never quite know what you will find until you open up the structure.”

Hamilton added: “We were also conscious of the Beenham Lockside collapse”. This was an uncontrolled collapse of an arch of this three-span form during its demolition in April 2012. An investigation is currently in progress. Hamilton says, “We took care with the demolition sequence, removing the structures evenly in metre-wide strips to keep the structural integrity”.

Demolition was carried out by Gilpin, who used four 30 tonne excavators working simultaneously at each of the three demolition sites. The piers were removed at Trenches and Old Stockley Road bridges. It had been planned to remove the piers to 500mm below sleeper level. However, this proved a little easier than expected as the piers were founded on Terrace Gravels some 200-300mm below the sleepers.

Missing the Mass

All works were completed and the track handed back by 16:00 on 26 December, well within the planned times. So, lots for the project to feel justly virtuous about. But there’s plenty more to consider, with tidying off the Christmas works and preparations for the next phase at Easter. Then there are a couple more potential reconstructions under consideration for next Christmas. Maybe, after all, there are easier ways to achieve virtue.

Sprout anyone?

Tunnels, railways, and the future for young engineers!

The Permanent Way is a diverse concept. There is the traditional formation, cess and drainage; there are embankments and cuttings, bridges and viaducts and, when necessary, there is the option, albeit an expensive and always a challenging one, to create a pathway by constructing a tunnel.

Very few tunnels are straightforward, each one having its own unique challenges and character. The excellent book by Thomas A Walker on the construction of the Severn Tunnel helps readers to understand the challenges engineers faced when tunnelling in the nineteenth century. A walk through Standedge Tunnel that links the line across the Pennines between Manchester and Leeds with the older canal tunnel below, or even a study of the mesmerising 3D maps of London’s underground stations and services, cannot fail to impress.

Many urban transport systems are heavily dependent on tunnels to provide an adequate pathway through the myriad of culverts, sewers, cable routes and piled foundations. Crossrail, probably the biggest engineering project in Europe, must be one of the most complex and challenging tunnelling undertakings today.

The Channel Tunnel provides the only high speed route from the UK into Europe. Plans for HS2 are being developed which will extend this route from London to the north of the country. To ensure that it is less invasive on the landscape and more acceptable to local communities, a significant proportion of the proposed route will be provided through tunnels.

Tunnel conference

Significant proposals are being developed involving railway tunnels across Europe and tunnelling is now becoming ever more popular in the armoury of options for a railway engineer and that is why THE RAIL ENGINEER attended a recent Tunnelling Conference held at the Institution of Civil Engineers.

The scene was set by Matt Sykes, ARUP’s leader for tunnel design, who focussed on the huge potential that tunnelling offers the civil engineer not only in this country but throughout the world. In Shanghai alone, at this moment, there are 39 Tunnel Boring Machines (TBMs) in the ground with a further 20 or more, ready to be put into operation.

As well as the major UK rail projects, Crossrail, HS2, London Underground upgrades and Light Rail, there are many others; power station new builds, cable tunnels, Thames Tideway Tunnel, Lee Tunnel and, taking just one example from abroad, the fascinating immersed tunnel project linking Denmark with Germany.

Investing in the future

The opportunities are clearly there and that is why the new Tunnelling & Underground Construction Academy (TUCA), based in Ilford, London, has been created. It is a key initiative designed to promote excellence in underground construction which will help to address the need for an adequate skill supply of young, innovative engineers to ensure that every opportunity is taken to maximise this potential flow of tunnelling work.

To highlight the emerging opportunities for young engineers, it was mentioned that when Brunel was only 20 years old he designed and built the first tunnel under a navigable river, the Thames Tunnel. He then went on to design and construct the then longest tunnel in the world, Box Tunnel, when he was 30. Will this next tranche of tunnelling projects offer similar opportunities for innovation for our emerging young engineers?

New build railways

Many projects were discussed at the conference, several of which were railway related.

Leading off with HS2, Tony Walker, railway business director for Mott McDonald, outlined the progress that was being made with this scheme. The first phase is the development of a Hybrid Bill that will be put to Parliament so that a final route can be agreed by 2014. This Bill will include the route selected, land required, initial design and environmental impact for a high speed railway to the Midlands.

Maintenance-Exploitation-8 [online]Within this first phase will be significant lengths of twin bore tunnel designed to accommodate trains running up to speeds of 400km/hr. To address the pressure wave gradient changes that will emerge from trains entering a confined space at such speed, porous portals will be constructed along with tunnel shafts every 2km. Although details are a little vague at this time, tunnelling between Euston and Old Oak Common and other locations including Amersham and Northolt offer in the region of 36km of tunnelling for the first phase.

Opportunities for young engineers

The overall tunnel mileage for this project will be significant. Last September, work started on the second phase of the project, extending the route to Heathrow airport to Manchester and Leeds. The plan is to complete phase1 by 2026 and stage 2 by 2033 – a significant period of work to excite any budding young tunnelling engineer.

During the phase 1 process, engineers will have to reconsider the concept of whole life costing for a tunnel. Many tunnels built in the Brunel era are still providing great value for money whereas some younger tunnel structures have caused problems. Quite rightly, HS2 is demanding a far more rigorous review of maintenance costs so that a truer value can be attributed to the overall cost of tunnel construction when compared with other options. It is possible that tunnelling could come out of this exercise in quite a favourable light.

A concise update of the Crossrail project was given by Paul Glass, technical director for the BAM Ferrovial Kier joint venture (JV). On the 118km route, 21km of the railway is within 7.1m dia. twin bored tunnels. There are three tunnelling contracts and the JV has the west end Royal Oak Portal to Farringdon Station section. Two tunnel boring machines (TBMs) are being used, one known as Phyllis and the other Ada, each about 150m long and weighing over 1000 tonnes.

A tight squeeze for Phyllis

Phyllis is now happily underground but it was a tight squeeze. The TBM had to be moved 400 metres into the portal at Westbourne Park. The journey started with Phyllis sitting on a transporter, passing under a footbridge which had to be jacked up in a possession. To progress further, the TBM was lowered onto skids to travel under gantries with a 12mm clearance, then once into the portal it was jacked down into the launch pit ready for boring. Subsequently, the machine has navigated bridge pile foundations, sewer culvert inverts, water mains, gas mains, the A40 flyover and the Hammersmith & City Line.

Once Phyllis had reached the Paddington Box, Ada followed and they are now both progressing under Hyde Park. Every movement and pressure change on both TBMs is monitored closely at all times. This includes face pressure, propulsion rate, cutter torque, belt weight and foam injection as well as grout volume pressure. Trends are being analysed continuously and checked against pre determined acceptable limits.

Monitoring movement

Precision instruments have been provided by specialist companies. One company, Soldata, is providing 75 Automatic Total Stations working in groups for up to 4 to 5 years within the areas that could be influenced by the TBMs. They are also providing water settlement cells, inclinometers, rod extensometers, tilt and crack meters. This is supported by a round the clock data management service.

Crossrail is using prisms to monitor rail movement and shape arrays for culverts. To date, ground movement has been contained to within 3 to 4mm and volume loss is 0.34%. They are both well within the specified tolerances and the 50mm per minute progress target for the TBMs is being achieved.

At Tottenham Court Road station and Bond Street, major changes are underway. Due to the congestion of tunnels in these station areas and the ever changing shape and incline of the tunnels over short distances, accommodating escalators, walkways, staircases, and service shafts has meant that sprayed concrete techniques are becoming very popular.

However, in some instances there is no option but to use old tried and tested mining techniques.

Keeping neighbours on side is a high priority and, unfortunately, some of the techniques used do have a tendency to create noise that can travel into adjacent properties. This calls on the skills of other suppliers such as Bruel & Kjaer which were keen to share their expertise in monitoring urban and industrial noise at the event.

Immersed tunnels

Moving further afield, an intriguing project shortly to go out to tender is the fixed link tunnel between the German offshore island of Fehmarm with the Danish island of Lolland in the Baltic Sea. The proposed tunnel link will be approximately twenty-one kilometres long and it will be made up of nine elements, each 217 metres long and consisting of two sections carrying a single railway line and two sections carrying a dual carriage roadway.

Each element will be constructed in a specially made harbour then floated out to sea, flooded and lowered into a dredged trench in the seabed. Water will then be pumped out of each element and they will be sealed together and covered. This will take place 35 metres below the sea level and will pose a significant engineering challenge.

The technique has been used before, but not to this scale. Invitations to tender for a design and construct contract will be issued early in 2013 and the project value is estimated at £4.6 billion. No doubt a strong consortium will be required to deliver such a complex undertaking.

For many experienced railway engineers, the thought of a railway tunnel conjures up an image of dark cold weekends, soot and grime, loose brickwork and falling stonework, bulging linings and sickly diesel fumes. That image will not disappear but there is now another world of tunnelling which involves new build, ingenuity, practical endeavour and prestige. It’s a real opportunity for any budding, young, engineer.

Luck by the Barrow load

If you’re going to have seven fully loaded aggregate wagons fall off the track just after Christmas, you really need a bit of good fortune to help you out. And luck can come from some surprising quarters. Perhaps it could be an obscure piece of railway kit that belongs to someone else that just happens to live a couple of miles down the track. Or perhaps it could even be a helpful local Scout troop.

Saturation point

It was wet around Christmas time. Not overwhelmingly wet, just winter wet. Trouble was that this Christmas soaking followed on from weeks of even worse weather and so just about everything that could be saturated was saturated. Most of our aging railway embankments have got used to being given a good soaking, but every so often it all becomes just too much to bear.

This is what happened just to the north of Barrow on Soar on the Midland main line. Originally a two track railway it was widened to accommodate four tracks – and the cheapest way to do it was to place (dump) large quantities of spent ash on either side. Ash was available in huge quantities in the nineteenth and early twentieth centuries and was used for all types of filling operations as well as for track ‘ballast’.SRDA 009 [online]

Cheap it may have been, but it can be a little fragile at times. Like many revellers after Christmas it too was a little fragile, but this time it was because of too much water.

Bank slip

When the railway system reopened for business after the Christmas break, the second train to travel south along the Up slow line was hauling a rake of twenty 100-tonne wagons containing mixed aggregate. The locomotive and the first ten wagons would have completed their journey successfully had they not been brought to an abrupt halt by the severance of the brake pipe. Behind the break lay the last seven vehicles, brought off the track when a 20 metre section of the ash bank slipped down by about half a metre.

The Slow lines were blocked. The phones started to ring. Receiving their post-Christmas phone calls were Richard Walker and Rob Lunn of Network Rail’s infrastructure projects team in Derby. They weren’t the only ones of course. Framework contractor Amalgamated Construction (Amco) was on its way with staff switched straight from emergency works in Wales and the west of England. DB Schenker was also on site, working out how to recover its wagons.

No access road

Many of our articles that cover track reinstatement mention temporary access roads and the involvement of neighbouring land owners. This time though there was to be no access road and little contact with the neighbours. It just wasn’t that sort of site. It was certainly difficult to get at, but Richard and Rob came to the conclusion early on that everything could be achieved using the existing rail access and by using trains. This certainly bucks the recent trend. Mind you it was pretty obvious right from the start that rail access was practical whereas road access certainly wasn’t. The team from DB Schenker came to the same conclusion for their wagon recovery. They too opted to work on their tricky operation from track level.

But before any earth could be moved or any track could be reinstated, it was necessary to find out what was going on in the embankment. The bank was given a good shave to get the dense vegetation out of the way and access steps were installed. The extent of the slip appeared to be defined, but piezometers needed to be sunk to check on the embankment structure and on its composition. Specialists from Pell Frishman interpreted the findings, defined the limits of the problem and drafted out a design for repairs to the bank.

Long-reach excavator

Barrow 032 [online]All the equipment made its way to site either as road rail machines or – in the case of Stobart Rail’s 360° long-reach tracked excavator – by loco-hauled low loader wagon.

Working its way carefully down the bank side, the excavator established a working area at the bank foot. Luckily it wasn’t necessary to acquire land as there was enough within the boundary line. This was a little ‘indistinct’ to start with and needed to be confirmed by the geomapping team in Manchester.

With the toe drainage repaired, the work of taking away the ash began. Fortunately it was possible for the arising spoil to be taken further down the line and placed as bank strengthening. This did away with the need to haul muck away from site.

No big yellow machine

Fetching in fresh fill to reinstate the bank appeared to be less straightforward. Dumpers, road-railers – it would have taken ages to complete. As luck would have it though, the Infrastructure Projects team has a wide spread of railway engineering knowledge – not just pure civils, but also track civils.

This side of the operation spends most of its life fetching and taking away prodigious quantities of stone and has a shrewd idea of what plant is the most appropriate. After all, the high output track relaying machine does not rely on dumpers otherwise it would be a laughably low output track relaying machine. The relayers feed stone to the site from a long rake of wagons and this was just the sort of kit that was needed. But there wasn’t a big yellow machine on the horizon.

Cooperation

This again is where luck helps out. Just down the track is the Lafarge Gypsum plant and tucked away in their sidings – which were also handy as the road rail access bridge head – was a stone discharge train (SDT). It may not have been yellow, but it was big and could handle respectable and continuous quantities of stone. Above all, it was available.

Thus an arrangement was made between Network Rail and Lafarge for the use of this bit of kit. Cooperation between all the parties involved ensured that the sometimes fraught process of running ballast trains at short notice went ahead without a hitch. Over two nights, with a steady discharge from two train loads of stone, the 1600 tonnes of new fill was carefully placed and compacted in layers.

Once up to level, track staff were programmed to reinstate the Up slow – initially with a temporary speed restriction of 20mph. By mid January and after final tamping and lining, the temporary speed restriction was lifted, the Up slow has returned to normal and the station at Barrow on Soar was able to reopen.

And the helpful local Scout troop? What was all that about? Well, they just happened to own a hut that became the messing facilities for the construction gangs and, being helpful, they have been suitably rewarded. So everyone had a bit of luck in the end.

Christmas at Milverton

Leamington Spa in Warwickshire is a cosmopolitan town famed for its café culture and its medicinal waters. This popular destination draws in plenty of visitors, many of whom arrive along the Leamington Spa and Coventry Line that crosses Milverton Viaduct. This 220 metre long structure was built in 1844 and is situated on the edge of Victoria Park, which was opened in 1899 in celebration of Queen Victoria’s Diamond Jubilee.

Today, the viaduct spans the River Leam, several public footpaths leading to the park and a roundabout. The masonry structure of the viaduct had been suffering from long term water ingress which was causing significant damage that would shorten its operational life if intervention did not happen.

Usually on schemes like this, the waterproofing is taken care of first and then any other planned remedial works can follow. However, such was the weakened state of Milverton Viaduct that structural repairs were needed just to get the viaduct in a fit state to withstand the impact of the core works that would need to take place.

Preparatory work

Work began late in 2012, just as the dark nights were taking hold. Principal contractor Story Contracting’s first task was to remove the thick undergrowth that had built up in most of the viaduct’s sixteen spans. Once that was gone, repairs to the masonry could commence. These included the usual mix of stitching, repointing and recasing, along with some highly skilled work rebuilding damaged feature stonework. The extent of deterioration in the structure meant that almost every square metre of each span required some sort of attention.

A variety of access methods was used along the viaduct’s length. Cherry pickers were the preferred option and, where ground conditions weren’t suitable for them, scaffolding was used. For the spans above the public highways temporary traffic management was needed to access the works which were carried out at night to minimise any disruption. Rope access techniques were adopted for the three spans that crossed the river.

Earlier works to strengthen the structure had included the installation of more than sixty tie rods through the spandrel walls and through some of the piers. On this scheme each of these tie rods was ultrasonically tested to ensure their continuing integrity. Several of the pattress plates were cracked or broken and repairs to these were completed before they were all blasted and painted in order to enhance their appearance and long-term life.

No Christmas dinner

The core waterproofing works were scheduled for a 129-hour possession beginning late on Christmas Eve. In the lead up to this Story Contracting established a trackside compound 200 metres from the southern end of the structure, near Leamington Spa station. This needed to be big enough for the 2,000 tonnes of new ballast, 150 precast concrete sections, and nearly 1,000 new sleepers that the project required, along with having space for all of the spoil that was coming off the structure.

Across the country Christmas arrived, turkey dinners were enjoyed and the core possession was underway. Story Contracting removed both tracks from the structure and excavated the ballast and fill material down to the new formation level.

The track removal works were sequenced so that the first line was removed by RRVs working from the one adjacent. Once the first line was out, the second was lifted using road-rail tracked excavators working on the ballast bed. When all of the rail and sleepers were removed the spoil ballast and fill material was excavated progressively back along the bridge towards the access. It was loaded into dumpers and transported back to the cut positions in the track where it was transferred into spoil boxes ready to be removed to the compound by RRV.

With the track gone and the fill removed the tie rods were now buried just below the surface. Their positions were identified and precise engineering control of the excavation depth was used to ensure that none were exposed or damaged by the plant working on the viaduct.

All of the works on the structure had to be carefully orchestrated throughout the construction process. Strict control of the position and movement of each plant item was enforced to ensure that none of the arches were unevenly loaded at any time.

Putting it all back together

One hundred and fifty precast concrete L-shaped parapet units, supplied by Ballymena-based Moore Concrete Services, were next placed along the entire length of either side of the viaduct on a screed bed that was laid to provide a level base and to set the height of the units. They were placed in sequence, working along the viaduct away from the access. As the installation of the precast parapets progressed, an in-situ cast reinforced concrete slab was laid that tied everything together.

Fortunately, the weather during the possession was relatively warm and the contingency measures that were in place to ensure the supply of concrete and its protection on site in the event of low temperatures were not needed.

Once the concrete had sufficiently cured, a loose laid waterproofing system was installed along the viaduct by specialist contractor VolkerLaser. This was lapped up the sides of the precast and welded to an insert in the concrete. At the ends of the viaduct, the waterproofing was tied into a new deck end drain that discharged to ground level soakaways.

The track reinstatement followed the track removal process in reverse. Ballast was delivered to the end of the viaduct by RRV and trailer from the compound. Dumpers forward-tipped the ballast onto the structure and it was distributed and levelled by a road rail laser dozer supported by a tracked RRV. Once fully graded and compacted, the first line’s sleepers and rails were installed. This then allowed the second line to be completed by RRVs running on track. RRVs fitted with a clamshell and hauling trailers full of new ballast then dropped the top stone before the tamper arrived, with a tamping bank attachment kept handy in case of tamper breakdown.

Welding and stressing was done and followed by a final run through with a profile bucket and a ballast brush. Guard rails were fixed to the new timber sleepers along the full length of the viaduct to complete the core works and the possession was handed back four hours early.

Story Contracting’s multi-skilled engineering and project delivery teams provided a full track and civil engineering service. On Milverton Viaduct this ensured that the entire needs of the project were integrated throughout the planning and delivery stages and removed any interface issues between trades that could potentially lead to difficulties on site.

The success of this integrated approach resulted in the Story Contracting team delivering the project ahead of programme, on budget and, most importantly, without any accident or incident.

Thameslink: Next Stop London Bridge!

Last spring, the rail engineer gave an update on the progress of the challenging £5.5 billion scheme to improve the Thameslink route through the heart of London from Bedford to Brighton. At the time, the Shard was just becoming a recognised feature of the landscape although it still wasn’t completed. It was also the time when everyone was looking over their shoulder excitedly, albeit with some trepidation, at the prospect of the London Olympics – a success or a national embarrassment?

Now however, for the not inconsiderable sum of £24.95, one can take a ride up to the top of the Shard and admire the view knowing that the Olympic Games were delivered on time and without incident, providing the country with something to be proud of. Down at ground level, work has progressed steadily to ensure that the Thameslink project continues to plan and budget, improving the journey for many thousands of commuters.

That project is now at the halfway stage and work is progressing well. Chris Binns is Network Rail’s head of engineering for the Thameslink programme and he is clearly still very enthusiastic about the project. He was eager to give a general update on progress, plus an outline of the next phases of work that will lead up to its completion in 2018.

Progress

The redesign of Farringdon station is now complete. Many buildings, including a 14 storey office block, have been demolished without incident, platforms extended to accommodate the 12 car trains and a new footbridge constructed to improve passenger connections with London Underground.

The existing station roof has been extended by 60 metres and an impressive new ticket hall added to the south. New lift shafts have been constructed that extend down to a level which will form part of the Crossrail service, linking into the station when the tunnel boring machines reach the station area sometime later in the year.

Blackfriars station has been dramatically revamped with its unique access points on both banks of the Thames. Chris wanted to emphasise that the station was opened to passengers in time for the Olympics in accordance with the plan. The installation of more than four thousand solar panels throughout the length of the newly constructed station canopies is now complete and delivering power into the station complex.

Balfour Beatty is the principal contractor for this work and Network Rail has recently completed additional structural repair work to the 1869 Grade 2 listed, five span arch bridge that supports the new platforms and station canopies. While already functionally complete, the final installation of glazing panels, waterproofing and snagging at the station are expected to be completed by the late summer.

Chris recalled the challenges that the short stretch of railway between Blackfriars and London Bridge stations posed for the team and he was delighted that they are now resolved to everyone’s satisfaction. This part of the project has certainly concentrated minds throughout, since there has been a need to extend the two track railway to four tracks through a short 350 metre corridor running alongside Southwark cathedral, over Borough Market and across the High Street before passing alongside the Shard and into the station complex at London Bridge.

Preparation for four tracks

It was a site that archaeologists as well as engineers wanted access to and some significant archaeological finds were made before the new structure was built by Skanska. The structure consists of six continuous spans of double track bridge with I-girders supporting transverse steel-concrete cross-girders with a concrete slab deck. In addition, a single span tubular steel bridge crosses Borough High Street leading up to the station. Just like the Shard, it is now part of the landscape spanning the beautifully revamped Victorian roof of Borough market and the recently reopened Wheatsheaf public house, minus its top storey! The plan is to bring the viaduct into use by August 2015.

An immense amount of planning and preparation has gone into both these landmark features and other work not detailed here including platform extensions, structural modification, track and signalling. At Borough Market alone there were 247 ‘party wall’ agreements produced and at one stage there were nearly 700 Network Rail delivery staff working on the Thameslink programme. This has now settled down to just fewer than 400 which, Chris thinks, will be the number required for the remainder of the project.

Conflicting movements

So, that’s the story so far. Currently underway is the total redevelopment of London Bridge station alongside essential changes to the track layout both east and west. To the east, work will extend out to the New Cross Gates area and include a new structure known as the Bermondsey Dive Under which will be completed by 2016. This will enable Thameslink trains to travel over Charing Cross lines without conflicting moves. Also, the track layout to the west will be reconfigured to ensure that Thameslink trains will be able to travel round into Blackfriars station independent of other train movements.

The team has full authority to proceed with this next stage with approval given by Network Rail and Department for Transport boards last November and receipt of ‘a letter of no objection’ from the Office of Rail Regulation in December. Costain has been appointed as the principal contractor for the station work by Network Rail, supported by WSP and Hyder Consulting for the design work. Balfour Beatty Rail has been appointed as principal contractor for all the track work and Invensys has been awarded the complex signalling design and installation contract, working with a dedicated Network Rail signalling design team for commissioning stage-works and fringe interface issues.

The architect for London Bridge station is Grimshaw and their remit has been to convert the existing split level, highly congested station with its six through and nine terminating platforms into one single level station with nine through and six terminating platforms all linked by escalators and lifts to an open concourse. The plan is for Platforms 4 and 5 to be dedicated to Thameslink and the new proposed track layout is designed accordingly.

Spacious concourse

To achieve this vision, Network Rail decided to go underground amongst the maze of Dickensian arches and this is where the new concourse will be constructed. It will extend right across the station from north to south running at right angles to the tracks. The space it will create is significant with football pitch proportions.

The platforms will be supported on viaducts over the concourse area and each platform will be protected from the elements by a simple canopy structure. Where the canopies span the concourse, northern light glazing will be included to ensure that the concourse area is light as well as weather proof.

High quality brickwork walls and arches will be constructed on the outside of the station both along Tooley Street to the north and St Thomas Street to the south. Everything will be brand new and, seen from overhead, the glistening new station platform canopies should appear as shining roots of the shard above. That will be impressive and if it works, it could justify the £24.95 ticket! It all sounds quite straight forward but there is just one minor detail to consider – how do you build the new station without interfering with day to day activities and allow London commuters to use the existing facilities, preferably throughout the whole of the project?

The answer is with great difficulty. However, so far, more than 50% of the old train shed roof has already been removed without any problem. A temporary crash deck has been constructed to protect passengers allowing the work to continue.

Staging diagrams

The team have produced detailed staging diagrams that cover all the work throughout the whole period from 2013 up to 2018. The detailed diagrams produced over the last two years of development go through ten key integrated station and track remodelling stages underpinned by large folders of detailed charts showing staging sequences and diagrams detailing each event down to the hour.

A minimum 14 day buffer has been built into each critical stage of the programme – one of the many lessons learnt through experience, something the team has been keen to do. Another example is that there is no longer any “man-marking” within the London Bridge station project. Instead, the most suitable person for the job is appointed, irrespective of their employer. So, where appropriate, Network Rail personnel will take instruction from Costain managers and vice versa. It all depends on what that team members have to offer, not who they work for.

According to Chris Binns, it is this partnering approach that will ensure that the project will be delivered on time and to budget. Also, it is the complexity of the project and the need to provide the level of detail necessary throughout the project that he and the team find so fascinating. Absolutely everything that is planned has a knock on effect which has to be understood, communicated, recorded and managed. As Chris emphasised, there is no other project quite like it and attention to every detail is absolutely essential.

New trains

Some actions are not within the direct control of the project team but are integrated into their plans. Enabling works are now underway to provide connections into the train depots required at Three Bridges on the Brighton line and Hornsey on the ECML in preparation for the arrival of the Class 700 although the DfT is responsible for providing the trains, the depot and of course, the Thameslink franchise itself.

Real progress is being made and so far Thameslink has delivered 12-car capabilities on the Midland Mainline and through the core area between St Pancras and Blackfriars. This includes major station rebuilding at Farringdon and Blackfriars. The railway systems in this area have also been upgraded to support the final capacity requirements that will eventually be delivered. It is good news so far.

The complete rebuild of London Bridge station will increase capacity for thousands of travellers during peak periods and, with the new Dive Under at Bermondsey plus the significant track realignment and associated signalling work, it will offer a logical path for trains, removing the conflicting movements that have frustrated train operators over the years.

There is a long way to go and many more engineering stories to tell but, with the enthusiasm displayed by Chris on behalf of the team, there is plenty of room for optimism.

Holding back the flood!

As you will be aware, 2012 was the second wettest year on record for the UK as a whole and, in England alone, it was the wettest year ever recorded. So it’s been a good year for the ducks, but for many people, including railway engineers, it has been a nightmare – especially in the south west. The last couple of months have been particularly challenging.

To find out more, the rail engineer spoke with Steve Hawkins, infrastructure maintenance delivery manager for Network Rail. Steve is based in Plymouth and, with a supporting workforce of over 300, he is responsible for the ‘Safety of The Line’ in Cornwall, Devon and parts of Somerset. Speaking early in January, he recalled how his team had coped with the challenges created by the monsoon rains that fell over the Christmas period.

Saturated ground

Rain had been falling consistently throughout the year, and Steve explained that they had already had to deal with a number of local flooding problems. However, by November 2012, the ground was saturated and the Met Office was issuing severe flood warnings on a regular basis throughout the area.

One of the locations that Network Rail was very concerned about was Cowley Bridge junction which is on the approach to Exeter from Taunton. The river Exe runs alongside the railway and passes under the branch line to Barnstable. When the river floods, water covers the fields either side of the junction leaving the railway formation stranded in the middle, surrounded by water. A large culvert, approximately 2 x 3 metres in section, normally carries excess water away from the site but, on 22 November, the volume of water in the river was so great that it lapped over the tracks, destabilised the formation and washed away the track ballast.

This is a location that is very vulnerable to flooding, and there was a similar incident about twelve years ago when ballast was washed away. However, this time the volume of water was far greater and not only did the water submerge the junction but it then proceeded down the tracks in the direction of Exeter station, flooding a relay room and fourteen trackside location cabinets, causing significant damage to the signalling equipment therein.

Assistant signalling engineer David Gill helped bring together a highly skilled team of more than thirty engineers from within Network Rail, McGinley and Signal Construction. This team worked round the clock testing circuits, replacing damaged S&T equipment and replacing about two miles of cables. According to Steve, it was a heroic effort from the signalling team and their permanent way colleagues whose work to restore the track by importing new ballast, stabilising the formation and realigning and consolidating the track ensured that the route was reopened three days later. The signalling, however, would take another two weeks.

Welcome hospitality

Alongside the junction is the Cowley Bridge Inn which was also flooded – not for the first time. The landlord cannot get the pub insured, but he was able to provide hot food, a roaring fire and shelter from the rain. Wellies were needed, even inside the pub, but the landlord’s good natured, friendly 24-hour service was invaluable and made all the difference over both the first challenging three days and the weeks to come.

Four days after the line was reopened in November, with the rain still coming down, Cowley Bridge flooded again. The track was once more washed out and all the signalling systems, which were still being worked on, were all under water again, as were the Looe, Newquay, Barnstaple and Heathfield lines. It was back to square one.

With the help of Infrastructure Projects and various contractors, the tracks were repaired again. The line at Cowley Bridge reopened after three days but with no signalling – this would take another three weeks of 24-hour working with the assistance of maintenance and project staff from across the country. During this period, the Network Rail operations team and the train and freight operators also had a challenging time, running a service without any signalling.

The hope was that Mother Nature would be kind and give everyone a chance to dry out and recover from this experience. No chance! There was a record to break and the year was coming to an end. Meteorological forecasts were ominous, rain continued to fall and, four weeks after the line was reopened, new flood warnings were issued. There was a great risk that all the good work would be wasted which clearly would be unacceptable given the additional disruption that this would cause. Something had to be done to ensure that the signalling equipment would be protected, but what should that be?

Great idea!

Steve suggested to his team that they should sacrifice the track and remove a section of it before the flood water arrived at Cowley Bridge to save the signalling systems. This was unchartered territory and Steve explained that it was time to consider and evaluate any and all ideas that were being proposed. During this process, assistant track maintenance engineer Craig Hocking proposed erecting a dam across the track between the junction and the signalling relay room instead of removing a section of track.

Craig suggested that the dam could be a flexible structure filled with water. After searching on the internet to see whether there was such a service available, the team came across a company which specialises in finding solutions to water-based problems. Additional good news was that they had three tubular cofferdams, similar to the ones envisaged by Craig, available in their warehouse in the Midlands. They were dispatched to site immediately.

So far so good, but the Met office changed the flooding prediction time. It was now only about ten hours before the floods were expected. The team needed pumps to fill the cofferdams with water but, as one might expect, all such available pumps had been hired out. More quick thinking was needed, this time from signalling telecom maintenance engineer John Tancock who suggested that they contact the fire brigade.

This they did and, by midnight with three hours to go, there were four tenders, a lighting tender, a control unit and 20 willing firemen on site pumping water into the cofferdams which had now arrived. Two of the dams were ready and in place, 80 metres from the relay room, by 02:45. Before long, the dams were holding back a metre head of water. Twenty four hours later, the third dam was ready and positioned as back up behind the front two, in case one failed. Sure enough, one did – so the last line of defence worked and saved the day.

It is the first time that this type of protection has been used and Steve is now developing a business case to purchase the appropriate equipment in case there is another attempt to break the rainfall record in the future. This is very likely given the forecasts from the Met Office about possible future rainfall patterns and intensity.

Not to be outdone

Dealing with all this flooding was probably enough to keep any sane railway engineer busy over a Christmas holiday, but in this case it was not the whole story. The cliffs behind the sea wall at Teignmouth were clearly determined not to be outdone by Cowley Bridge and, on 27 November, there was a landslip with 1000 tonnes of material cascading down the cliff toward the main line railway. Fortunately, it fell in the cess and behind the fence that runs parallel with the tracks.

The fencing did its job of catching the landslip but it was badly damaged in the process. Only six hours after the start of the flooding at Cowley Bridge in December, another 1000 tonnes of rock and rubble came down, this time completely wiping out about twenty metres of fence and spilling onto the tracks.

Network Rail’s hard-pressed maintenance team employed the services of the regional contractor Dyer and Butler to clear the track and remove the debris from site. The line was closed for twelve hours after which it reopened with a 20 mph speed restriction that, at the time of writing, is still in place.

Other lines in the area were similarly affected. Twenty six washouts were recorded on the Looe Branch in Cornwall, all of which have now been repaired. The situation was similar on the Barnstable Branch which experienced twenty two washouts between Eggersford and Barnstable. Some were quite significant and the line was not reopened until early January 2013.

Overview

On Boxing Day, Steve managed to acquire the services of one of Network Rail’s two helicopters to survey the main routes, check the condition of the fence lines and gain an overview of the lie of the land. Where water was evident, he could estimate the likelihood of it affecting the railway in the future. Throughout this challenging period, Network Rail worked closely with the TOCs and FOCs. The Met Office continually provided forecasts and weather warnings which Steve and his team followed diligently. Everyone worked together and different teams combined and performed effectively. There where no accidents and everyone arrived home safe every day.

Some engineering lateral thinking proved invaluable and Steve ensured that ideas from the team were listened to, valued and evaluated.

At the end of the day, the dam at Cowley Bridge worked which was a satisfying outcome for a team of dedicated railway engineers who had experienced an interesting Christmas, although not one they would like to repeat.

Here’s to a dry 2013!

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