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Plumstead portal box construction

As was highlighted in the accompanying article on Crossrail’s Thames tunnels, one of the challenges involved was agreeing a way to construct the portal box at Plumstead.

The box was to be some 300 metres long and, at the deepest point adjacent to the portal itself, around 25 metres deep. Its south side was to lie parallel to the railway out of London Bridge towards Woolwich and Dartford and was to be only about six metres from the nearest track. These tracks carry South Eastern Trains’ services and freight traffic, at very frequent intervals, and disruption just could not be tolerated.

Falling foul of standards

Network Rail standards concerning works like these alongside the railway were very restrictive, following the same principles as had applied for many years – back to British Rail days. Cranes and similar plant were not permitted to work where they might fall foul of the running lines. Detailed provisions applied, but in essence, no such equipment was to work facing the line or at an angle to it such that the jib, load or other part it would foul the line should the machine fail or overturn.

The portal box sidewalls were to be constructed in a combination of secant and diaphragm piles. The secant piling rig was considered and deemed acceptable to work even in this tight spot, since it was a hydraulic machine which could have the check valves and hydraulic fall arrest systems that Network Rail required in order to agree to its use in such circumstances. The diaphragm wall piling rig was a different beast. It is considered a crane as the grab it carries, three metres long and one metre wide, is suspended on ropes – just like a crane. The sort of constraining equipment used on the secant rig was just not applicable to this machine. Further, the piles required steel reinforcement cages, around 20 metres long, to be lowered into them using an auxiliary crane.

With 150 piles along the side of the box, constructing the track side wall under night time track possessions was not a feasible solution to this problem, and some other ideas needed to be considered.

Working through the problem

Fortunately the Crossrail team, led by John Kinnear and Simon Chittenden, foresaw the problem in advance, and in September 2010 discussions began between them and Network Rail’s principal engineer – Crossrail, Steve Brame. He involved the Network Rail asset protection team led by Geri Quinn.

When the Hochtief/Murphy Joint Venture (HMJV) was appointed in April 2011, the discussions began in earnest as the HMJV was able to suggest realistic, practical options for mitigation of the problem. Andreas Raedle, HMJV technical risk manager, and Paul Baker, HMJV rail interface manager, represented the JV while engineers George Christou and Tom Smith took the technical lead for Network Rail.

It was quickly established exactly how the HMJV preferred method of working would be non-compliant with the relevant Network Rail standards. Collaborative, open discussions ensured that all parties understood the options that had been considered in arriving at the preferred method of working, the reasons why certain of these had been rejected, the resultant non-compliances and the mitigations that might be adopted.

Everyone was clear that the mitigations adopted must not just transfer the risk somewhere else, they had to achieve genuine and significant risk reductions. An iterative process developed the final derogation that was proposed to Network Rail for their acceptance and ratification.

It was clear early on that the two key aspects were the diaphragm wall rig and the auxiliary crane, either of which might fall foul of the line.

Proposals and derogations

Consideration was given to relocating the portal box away from the line, but the constraints imposed by the listed status of White Hart Depot precluded this option. Construction of such a massive wall would have meant so many night-time possessions that the disruption to the rail service would have been unacceptable, whilst the delay and cost implications for Crossrail would also have been intolerable. Risk assessments also suggested that so much night time working would have caused a very significant increase in risk compared with predominantly day time working.

The suggested mitigations to support the proposed derogation included:

  • Additional inspection and maintenance regimes for the diaphragm rig and its auxiliary crane, to reduce the risk of failures;
  • The use of heavier machines downrated to the required capacity, again to reduce the failure risk by ensuring that the machines were significantly less stressed than normal;
  • The construction and use of substantial reinforced concrete platforms for the machines to stand on to work, to reduce the risk of overturning;
  • The provision of attendant rail safety staff to monitor the works and carry out emergency procedures in the event of an incident;
  • The production and implementation of detailed, comprehensive emergency procedures and communications systems in case of an incident;
  •   All working to be restricted to daylight hours.

The HMJV found this last mitigation to be too restrictive given that the work was going on in winter, when the days were very short. Evidence was produced which actually showed some increases in risk resulting from the daylight hours restriction, meaning that it was not as effective in reducing risk as had been thought. For example, there was the risk that pile excavations could be left incomplete overnight because of the short working day, resulting in the additional risks of excavations left open. It was agreed that the restriction to daylight working be removed with the installation of a reactive warning system which triggered both audible and visual alarms should the asset protection barrier be breached, alerting the attendant safety staff.

After several iterations between the parties, an agreed draft derogation against the Standard was finalised. This was submitted to Steve Brame, who accepted it on Network Rail’s behalf.

Successful result

Implementation involved the documentation of the derogation and the necessary revised working methods, a significant effort devoted to the review of things like crane operation diagrams and a comprehensive programme of briefing staff about their responsibilities. The latter gave particular emphasis to the agreed emergency procedures, and included regular auditing and reviews to ensure that everyone knew their roles. Paul Baker was heavily involved in this element on behalf of the HMJV.

The outcomes were good. The work was completed on schedule in mid 2012, a pretty good result in itself. There was only one occasion when the emergency procedures were implemented ‘for real’. This involved a minor spill of bentonite onto the track. Fortunately, no train was in the vicinity and the spill was not great enough to require any suspension of the train service. HMJV reacted very responsibly, suspending work for 36 hours whilst the causes were reviewed and for revised procedures to be agreed and put into place.

The negotiation and successful implementation of this derogation to the Network Rail standard was a very significant step. It was the first time that such a derogation had been attempted, and it showed that such a change in approach was achievable by agreement and in action on site.

Issue 107 – September 2013

Listening for failures

Premature corrosion of steel tendons in post-tensioned pre-stressed concrete, cable stay and suspension bridges can cause them to fracture, compromising the strength, integrity and service life of the structure. There are many bridges of these types not only in the UK but worldwide, so how can infrastructure owners obtain information on the condition of their structures, whether they are deteriorating and, if so, the rate at which they are deteriorating?

Currently, to obtain information on their condition, these structures are subjected to in-situ special inspections which include intrusive drilling into a sample of the ducts of post-tensioned concrete bridges or, in the case of cable stay and suspension bridges, unwrapping the protective covering and undertaking a visual examination of the tendons.

While such inspections give an indication of the extent of the damage caused by corrosion, the risk of further fractures then has to be managed. Where there is deemed to be a risk of corrosion and fracture of tendons, interim measures such as lane closures or weight restrictions may be applied. However these measures can increase congestion, extend journey times and increase CO2 emissions.

An alternative is the use of asset management tools such as SoundPrint®. This is a non-destructive acoustic monitoring system originally developed by the Canadian company Pure Technologies Ltd to detect wire breaks in unbonded (ungrouted) tendons in the floor slabs of office buildings. When applied to bridges, this system can assist the bridge owner in developing a management strategy for the structure. Research and application by Pure Technologies Ltd, in conjunction with TRL, has seen the system being used as a structural monitoring tool in the United Kingdom since 1998.

Development of SoundPrint

In 1992, the Department of Transport (DoT) placed a moratorium on the construction of post-tensioned concrete bridges with internally bonded tendons and initiated a programme of special inspections of this type of structure. This followed concerns about the premature corrosion of the steel tendons.

In addition, the DoT, and subsequently the Highways Agency (HA), undertook a programme of research into methods for detecting corrosion and fracture of wires in post-tensioned tendons. As part of this research, TRL was commissioned to undertake trials to investigate the use of SoundPrint for detecting wire fractures in tendons in grouted ducts. The findings from the trials provided independent verification that the SoundPrint system could be used to detect and locate wire fractures in steel tendons in grouted and partially grouted post-tensioned concrete beams.

Supplementing the laboratory tests, the HA also funded a one-year field trial of the system which was implemented at the Huntingdon railway viaduct – a six span post-tensioned bridge in Cambridgeshire carrying the A14 (Cambridge to Kettering section) over the electrified East Coast main line and a local single carriageway. Initially, an array of 32 acoustic sensors was installed, predominantly on the northern cantilever span but also on the northern backspan of the bridge. Trials of the system, including blind trials using facsimile breaks and external wire breaks, proved that the system was working as intended.

The field trial proved so successful that HA commissioned TRL to continue monitoring the structure using SoundPrint to assist with the long term management of the viaduct.

In 2009 a major upgrade of the system was undertaken and the monitoring now comprises 112 acoustic sensors encompassing the north and south cantilevers and the north and south backspans. Monitoring of this structure is now in its 16th year.

Acoustic monitoring

For acoustic monitoring to be useful and effective, it has to provide information over many years and has to be continuous, effectively being able to capture critical data 24 hours a day. In addition to this, certain challenges have to be overcome and a number of important conditions must be assured, including:

  • Independent verification of the applied techniques – SoundPrint is currently the only independently verified system in the UK;
  • The ability to monitor operational structures and have a high system uptime;
  • The ability to manage large volumes of data and diagnose system problems using state of the art techniques;
  • Comparing data to known acoustic events;
  • Timely reporting of the information to owners and engineers.

Within the structure, the post-tensioning strands contain a significant amount of potential energy in the form of prestress. When a wire in a strand breaks, the potential energy is converted into kinetic energy, which is suddenly injected into the structure, detectable as a dynamic response. The result is a series of multimodal vibrations of the concrete structure itself. These events are detected using an array of sensors and the resulting data continuously analysed using proprietary software/hardware to detect acoustic signatures similar to known wire breaks. Flagged events are compared to a database of over 2000 wire breaks, and confirmed by an experienced data processor. Active failures are reported to decision makers responsible for the structure.

The measures used to analyse the signals are manyfold, and are derivatives of time- frequency analysis popularised in electrical engineering disciplines over the past 30 years.

An important parameter used to discern between ambient noise and wire breaks is an autocorrelation of the time-frequency- energy representation of a signal to known wire breaks captured on similar structures. Another useful parameter that can be calculated using time-frequency analysis is the absolute amount of energy captured, which is proportional to the size of the wire break.

Where the structure remains ‘quiet’ (low number of wire breaks) it gives an assurance to the bridge owner/operator that it is not deteriorating rapidly. If failures are detected, and taking structures out of service immediately would cause large- scale disruption, continuous monitoring will allow structures to remain in-service while maintenance or replacement options are developed and budgeted.

Huntingdon trials

The Huntingdon railway viaduct was constructed in 1975 and crosses a local single carriageway, the electrified East Coast main line and part of the passenger platform at Huntingdon Station. It is a six-span structure which forms part of the Cambridge to Kettering section of the A14 dual carriageway. Spans 1, 2 and 6 are simply supported reinforced concrete beams and spans 3 to 5 are of post-tensioned beam construction. The main span (span 4) consists of a 32 metre-long suspended span which sits on half-joints formed at the end of two 16m long cantilevers extending from the adjacent piers. The remaining five spans are 32.3 metres in length.

A special inspection undertaken in 1994/5 discovered the presence of voids, water and chlorides in the tendon ducts of the cantilevers (span 4) and back spans (spans 3 and 5) of the viaduct but no significant corrosion of the strands. There was concern that such conditions could allow the corrosion of the post-tensioning strands to develop to such an extent that they would break. However, as the prestressing system was apparently in a good condition, the structure had a long potential life but required careful management. The high volume of traffic using the route made it essential to maintain the structure in service with minimum interruptions whilst maintaining an appropriate level of safety.

Monitoring

The half-joint was the region considered most likely to benefit from an assurance about tendon condition as half-joints are difficult to inspect. Also, the two cantilevers contained no geometrical redundancies in respect of shear failure in the half-joint and failure over the pier in hogging flexure. It was therefore decided that early detection of wire fractures, or evidence that none were occurring, would assist the long-term management of the viaduct.

The western cantilever was preferred to the eastern cantilever for monitoring as access to the cantilever section and half-joint only required lane closures on the local carriageway and a hydraulic access platform. This was considerably more straightforward than obtaining access to the eastern cantilever which partially spans the railway line.

A SoundPrint acoustic monitoring system was installed on the viaduct in mid-1998. As this was the first installation of the SoundPrint acoustic monitoring system in the UK, one of the objectives was to assist in the evaluation of the system as well as providing data on the condition of the viaduct. It was anticipated that the presence of the noisy expansion joints at the two half-joints of the viaduct would provide a great many acoustic events and present a considerable challenge to data collection and analysis. This was investigated prior to installation of the system on the bridge using a sensor installed temporarily on the deck. A Schmidt hammer impact was recorded and played back through the acoustic monitoring equipment, and it was found that the impact could be readily discerned from the background noise. In addition a number of facsimile wire break events were created as part of the commissioning trials.

In total, 36 sensors were installed on the western cantilever and anchor span. The sensor array was designed with the objective of detecting wire breaks in partially grouted tendons at the half-joint and over the cantilever span, but nevertheless was expected to detect wire breaks in fully grouted ducts.

The monitoring system was extended in 2009. Sixteen additional sensors were installed on the anchor span of the western cantilever and the sensor array was replicated on the eastern cantilever and anchor span.

The structure is still in service 15 years after the installation of the system. For the period between its installation in 1998 and 2005 no wire breaks were detected.

This provided a reasonable level of certainty that prior to the installation of the system in 1998 no wire breaks had occurred in the area covered by the system. Since 2005 a small number of wire breaks have been detected but not enough to cause concern about the integrity of the structure.

Alternatives

If the acoustic monitoring system had not been available, it would have been necessary to have installed a broader regime of strain measuring devices around the structure to detect changes in behaviour that reflect losses of post-tensioning. It may also have been necessary to take routine x-rays of key areas of the structure to try to detect wire breaks.

Such an approach would not have provided the same level of confidence as the acoustic monitoring system and would have required a number of closures of the structure.

Report by Kevin Barker, senior project engineer , TRL

Dinmore Tunnel – Suck it and See

Dinmore tunnel is actually two railway tunnels located on the former Shrewsbury to Hereford line between Hereford and Leominster. The tunnels are split level with the track on the Up line to Leominster being higher than the Down line to Hereford. The Up tunnel was built in 1853 and the Down tunnel in 1891. Both tunnels are approximately 1,000 metres long. The line speed through the tunnels is 80mph.

Maintaining track

It would be difficult to think of a more challenging location for Network Rail engineers to carry out maintenance than in a long single bore tunnel. If the drains are clogged up, the formation saturated, the ballast riddled with pumping red clay and there is nowhere to move the CWR or the concrete sleepers, there are not many options. They could spend the next twelve months hand-digging the contaminated ballast out but it would be tedious work, progress would be slow, temporary speed restriction would be necessary for long periods of time and it would be expensive.

A Kirow Crane could lift sections of track out in front of itself and then diggers could remove the contaminated ballast, but how would they get the ballast out of the tunnel? They might have to consider welding rail (in a tunnel) and then possibly destressing the track. It all gets very complicated, expensive and, whatever method was chosen, the effect on the train service would be detrimental to say the least. Worst of all, it is quite probable that the drainage system through the tunnel, often the root cause, will still remain ineffective.UK Ra2 4 cropped [online]

Newly-designed RailVac

Ian Harris, Network Rail’s assistant track maintenance engineer, Hereford, was the man with just this problem. The track formation within the Down tunnel was suffering from poor drainage and contaminated track ballast which was making it very difficult to maintain the track within acceptable parameters for the line speed specified.

To address these problems, Network Rail decided to utilise a RailVac machine owned by Railcare, Sweden. This machine gained product approval just over twelve months ago and it is a development of a Swedish UIC model which has been used in this country since 2006. However, that machine had to be transported by road because it did not comply with the UK structure gauge.

Railcare, working in partnership with Bridgeway Consulting, successfully steered the newly-designed machine through Network Rail’s robust product approval process. It is now classed as a flat wagon when forming part of an engineer’s train so can travel at up to 100km/hr. When working independently within a possession it will travel at a maximum of 16km/hr. Steve Mugglestone is Railcare’s project manager responsible for the RailVac, its performance, productivity and future workload. He explained the scope of work that Network Rail wanted carried out during a 48-hour possession.

The work included the excavation and re-ballasting of approximately 200 metres of plain line situated in three separate areas, to clear the channel drain and remove the contaminated ballast shoulder throughout the length of the tunnel. Steve explained that a road-rail vehicle (RRV) fitted with a clamshell bucket, located at the south portal of the Down tunnel, loaded ballast that had previously been stock piled in the cess onto a road-rail dumper. This was fitted with a conveyor belt that could offload ballast across the formation, in front of the dumper. It is a simple but very useful item of plant supplied by A P Webb Plant Hire Ltd.

At the north portal of the tunnel was another RRV, also fitted with a clamshell bucket. Its role was to manage the excavated material, dropped off by the RailVac after working in the tunnel. When all the work in the tunnel is completed the RRV would then load the material into empty wagons to be taken away.

The RailVac itself was brought to site as part of an engineering train, along with the wagons. They were detached ready for work whilst the train completed a run round so that it was in position to pick up the RailVac and wagons at the end of the possession. So when all movements of the machines and train have been completed the engineering supervisor gave permission for the RailVac machine to commence work.

The ‘Manipulator’

The RailVac is similar in size to a tamper. It has an engine, cab, generators, pumps and valves designed to create the required vacuum and suction as well as two hoppers, all neatly designed and packed away. Then you notice the vacuum machine ‘Manipulator’ which has a long 250mm diameter flexible tube with two metres of hardened steel nozzle at its end. It is a bit like an elephant’s trunk and its function is very similar in that it sucks up anything that is within 50mm of the nozzle end. Nothing gets missed, especially life-expired ballast contaminated with wet pumping clay from the formation.

The RailVac has all the necessary requirements for safe working – cameras, lights and electric sensor beams that can stop the machine if it is moving too close to another object. It can move in either direction but is planned to reverse away from the excavated track with the operator standing at the cab end of the machine where it is possible to control the movements of the vacuum manipulator by means of a ‘remote control box’. This is clearly a skilled activity, preferably performed by a person who has gained considerable experience using game machine controls. Certainly the operator in control at Dinmore was very adept, ensuring that everything from around and under the sleeper was sucked up by the Manipulator down to a depth of between 250 and 300mm below sleeper bottom.

Loading fresh ballast outside the tunnel portals (Collin Carr) [online]

Depending on the condition of the ballast being removed, the machine will work for about 1.5 hrs sucking up about 18 cubic metres of spent ballast and clearing about 15m of track and shoulder. Try doing that with a shovel! There are two operators who share the task of operating the control box. The debris is sucked into the hopper positioned in the middle of the machine. The RailVac then travels out of the tunnel, the hydraulic hopper doors open, deflector plates are extended out below the hoppers and vibration helps the spent ballast to be discharged for the RRV to deal with.

Although the machine moves at a very slow pace an exclusion zone of six metres is set up and maintained around the machine as it works. The only personnel working in the immediate area of the machine are the operator, the machine controller and technical personnel. However, because of the nature of the work, usually two additional track workers follow the machine with rakes to ensure that all the debris is sucked up. If necessary the machine stops to enable this work to be done safely. It is a tight operation with only 5/6 additional support staff needed. Steve uses people who are now familiar with the process, supplied by Quantum Construction Leeds.

Ballast vibrators

To ensure that line and level of the track is maintained, Duff jacks are placed between the RailVac and the ballast discharging dumper which is distributing the ballast from its conveyor belt in 100mm layers across the excavated formation. The ballast is then vibrated using handheld Robel tamping machines that are similar in size to Kango packers and are designed to vibrate rather than compact the ballast. They only recently started to use these machines but, so far, they are very pleased with their performance.

Once the heavy excavation work is complete, the RailVac removes the ballast covering the drainage troughing lids which are then manually removed so the machine can suck out all the debris. It’s a simple job with the RailVac but it is often the critical job that does not get done when other methods of repair are used. When all the work is complete and the site cleared, a tamper runs through the tunnel to ensure line and level are within tolerances, ready to receive the first train at the end of the possession. A TSR of 50/30mph is applied initially then raised to 80mph the following week after a further tamp.

As Steve explained, the beauty of this process is that at the end of the shift you have a clean, tidy site and the track is fit for purpose. They have never overrun a possession with this or the previous machine. No cables need to be disconnected so there is no signalling involvement and, if need be, they could hand back a possession at short notice. The process is ideal for all those locations, such as S&C layouts and underbridges, which are most difficult to maintain. Certainly Ian said he was very pleased with the work that they were doing.

A few more of these machines may be seen around the network in the future. For maintenance engineers with a problem that possibly keeps them awake at night, they might want to try the RailVac. Suck it and see!

National Rescue

Many regular rail travellers will have experienced that sinking feeling when the train they are waiting for doesn’t arrive. First of all interest, then concern, followed by worry, despair and finally anger.

With the modern passenger information systems at stations these days, at least people know what’s going on. “Points failure at Peterborough”, “Signalling problems at Slough”, “Wiring down at Watford” and, worst of all, “Leaves on the line at Leatherhead”.

All of these are infrastructure failures. Network Rail, as infrastructure owner and as reported many times in The Rail Engineer, is working hard to minimise these problems and the delays they cause. And the train punctuality figures are slowly creeping up as a result.

Failed trains

But some 20% of delays are actually caused by the trains themselves. Often that is simply what it is, a delay, but a completely broken- down train can cause real headaches, not only for the passengers on or waiting for that train, but for all the other trains that get stacked up behind the failed one.

What is needed is a way to get a dead train off the running line as quickly as possible, so that the following services can continue on their way. Also, any passengers on that train have to be taken to a safe place to disembark. The obvious way of doing this is to use another train to drag the failed one out and take it to the next station. However, that’s not as easy as it sounds.

Class 57 Coupler Mods 002 [online]

Modern trains are complex animals. They are designed to work as a unit – even adding extra coaches is a complicated process which has to be carried out in a workshop over several days. That means they aren’t really set up for receiving outside assistance.

For a start, different train manufacturers use different couplers. So, just fastening on to a train can be problematic. Then, in these days of ‘fly by wire’ systems, everything is controlled by train management systems and those are different for every class of train out there.

The easiest way to collect a failed train is therefore to send a sister train out to connect to it. This will have the correct couplers and the correct electronic systems. However, one may not be available. The rescuer will use the same power source (overhead wires, third rail) as the stranded train and, if there has been some damage to that or the power has been switched off, then it will be useless. And finally, having a rescue vehicle that could be 250 feet long may be unhandy in some circumstances.

Thunderbirds have gone

To address these problems, Virgin Trains kept a fleet of rescue locomotives close to the West Coast main line. These Class 57/3 locomotives, known as Thunderbirds with names such as “Scott Tracy” and “Lady Penelope”, were fitted with Dellner retractable couplings and could connect to both Pendolinos (Class 390) and Super Voyagers (Class 221). In addition to rescue duties, they were used to haul Pendolinos along routes without overhead wiring, extending the range of these trainsets. However, as these requirements decreased, the locomotives were returned to leasing company Porterbrook towards the end of 2011.

Network Rail acquired six locos for use hauling its winter de-icing trains, earning them the nickname “Snowbirds” – a reference to their Thunderbird origins. They were also used on test trains.

However, the rescue role was never very far from Network Rail’s mind. Mick Stewart, senior fleet engineer, and his team at NDS (National Delivery Service) worked on a plan to use these locomotives to recover stranded trains, mainly electric multiple units (EMUs) in the south of the country.

The Dellner couplers were retained on four of the locos, although they were lowered by about 100mm as Pendolinos have a particularly high coupling. The other two locomotives were fitted with Tightlock couplings. Planned by Network Rail in conjunction with Porterbrook, the work was carried out by Brush at Loughborough.

Compatible systems

A bigger challenge was to get the locomotives ‘talking’ to the electronic brain of the stranded EMU. Originally built as Class 47s in the 1960s, they were rebuilt as Class 57s at the end of the 1990 with the original Sulzer diesel engines replaced by EMD units. As a result, they are fairly unsophisticated locos with mechanical controls, ideal for accessing areas of the network where electrical power may be out, but not much good at interfacing with a modern, electronic, train management system.

Virgin Thunderbirds DSC_3112 [online]

So the project team (NDS working with Porterbrook and Atkins) concentrated on fitting pressure switches and pickups so that control commands could be sent to the stranded train. Using various adapter cables, the Class 57/3 can now feed 110V power to the EMU and also control both brakes and door opening systems. Compressed air can be fed to the train if its own compressors are offline.

The rescue locos normally deploy from their base at Eastleigh with a crew of two.

All necessary frames and cables are stored in the old boiler compartment. To connect to the stranded train, the driver handles the loco while the crew oversees the coupling up and other connections. These are best done by two people, removing the need for anyone to duck through under the coupling, so the driver of the stranded train is usually drafted to assist under instruction.

Once connected, there are two possibilities. If the train is completely dead, it can be hauled out to a place of safety at low speed. However, if all systems are running and controlled from the 57/3, then the consist can operate at line speed. Although it will probably only run to the closest station, it is actually quite capable of operating the originally intended service.

To test this capability, a four-car Class 377 was hauled from London to Brighton and back last summer, at service speed, with no problems. It ran round at Brighton in 15 minutes, ready for the return leg, with a crew of four (Class 57 driver, Class 377 driver and two fitters).

The fleet can currently rescue the Electrostar family of Class 375, 376 and 377 trains (including Class 357 operated by C2C), the Desiro family (Classes 350, 444, 450), and Classes 317, 319 and 455.

With the ability to couple up to a stranded train and be on the move again within 15 minutes, the speed of recovery has noticeably improved since the new fleet was commissioned. There are plans to stable these useful locomotives around the network, reducing response times still further. Not a bad use for a class of locomotives that is now fifty years old.

Crossrail TBM poised to begin next phase of Thames Tunnel

Crossrail TBM Mary has broken through into the Woolwich station box, marking the halfway point in tunnelling works south of the river.

Mary, who began her stint in May, joins Sophia who is currently being prepared to continue tunnelling beneath the Thames to North Woolwich.

Sophia and Mary are constructing Crossrail’s the Thames tunnel which will created a link underneath the river between Plumstead and North Woolwich.

Since starting work in May, Mary has excavated 110,000 tonnes of material.

Gus Scott, project manager for Crossrail’s Thames Tunnel, said: “It’s great to know that we’re half way through our tunnelling in southeast London. Mary and Sophia have done a fantastic job so far, between them constructing a mile and a half of brand new tunnels from Plumstead to Woolwich.”

Rail’s carbon footprint

Does carbon matter to rail? This was the question posed at a recent seminar hosted by the Institution of Mechanical Engineers (IMechE). Delegates from across the rail industry gave their response, presenting a mixed message on how the UK’s railways need to adapt to reduce their carbon footprint … or not.

When it comes to green credentials, or to be more specific, the size of its carbon footprint, the UK’s railways have a pretty good start. Let’s try to put it into context. The UK churns out 520 million tonnes of carbon dioxide (CO2) annually. That sounds a lot, and it is, but on the global scale it’s a relatively minor amount. In the league of carbon producers, China takes the lead with 7,711 million tonnes per year, followed by the USA with 5,425 million tonnes. By comparison, the UK is a mere ‘also ran’, accounting for just 1.7% of the total world output. Roughly 25% of the UK’s carbon output can be attributed to transportation and rail is responsible for just 1.8% of that. Without becoming too much bogged down with the figures, suffice it to say that the UK rail network accounts for about 0.0076% of the world’s CO2 production. So, in terms of carbon, is rail a problem, or might it provide a solution?

Published targets

As part of the Kyoto agreement the EU has set targets for the reduction of greenhouse gasses (GHG) – mainly CO2. For 2050, the EU objective is to reduce Europe’s GHG emissions by 80-95% compared to 1990 levels. The Climate Change Act 2008 reinforces this – indeed goes beyond it – and the UK is committed to a 34% reduction in GHG emissions by 2020 and 80% by 2050.

The objective is to offset the massive increases in emissions from developing industrial countries such as China, India, Brazil and others. The EU says that developing countries have a right to develop. In China, emissions are up 170% since 2000, but there can be no limitation until GDP per capita (the value of goods produced per person) reaches $25,000. Currently, it is £5,000.

Meanwhile, car ownership is rising and China plans to build another 363 coal fired power stations. India plans to build 455, the worldwide figure is something like 1,200 and, as is common knowledge, greenhouse gas emissions have been linked to global warming and climate change.

Although the UK has been cutting emissions at home, it imports goods that produce CO2 in these other countries, pushing up emissions from there. The UK is the second highest importer in the world of these so-called ‘embodied’ emissions. Bearing that in mind, strong action is needed in transport if the 2030 and 2050 targets are to be met: transport is the only sector in which GHG emissions have risen since 1990 (by 19% overall). The European Commission’s strategy for meeting the 2050 reduction goal in transport was set out in the 2011 Roadmap to a Single European Transport Area – Towards a Competitive and Resource Efficient Transport System (the ‘Transport White Paper’).

Cleaner transport

A key point in the Roadmap for all transport modes is that transport needs to use less energy and to use cleaner energy. Future development in transport must rely on improving the energy efficiency performance of vehicles and developing and deploying sustainable fuels.

It is recognised that standards are needed for CO2 emissions of vehicles in all modes, supplemented by requirements on energy efficiency where necessary. Significantly, energy use reduction goals are to be considered for cars, road freight, and aviation – but not for rail!

Specific Roadmap targets for the rail sector are: » Facilitate ‘efficient and green freight corridors’;

» Triple the length of the existing high-speed rail network by 2030, and complete the network by 2050;
» By 2050, the majority of medium-distance passenger transport should go by rail.

In terms of carbon emissions, rail movement is somewhere between two and five times more energy efficient than road transport. Rail’s share of transport GHG emissions is 2%, while rail’s market share is 6% (passenger) and 10% (freight).

Modal switching in favour of rail therefore seems to make sense. In fact, it is an important part of emission reduction strategy. The target is to shift 30% of road transport over 300km onto rail by 2030, and 50% by 2050. Through maximising use of existing infrastructure alone, a 30-40% growth in train- kilometres by 2020 could be accommodated. Taking into account projected demand for 2020, rail freight traffic could still grow by
28% and passenger transport by 38% over the whole European network.

There is particular scope for rail to increase its market share in certain segments such as international containerised transport. In freight transport, up to 20 million tonnes of CO2 (7% of freight transport emissions) could be reduced by modal shift of traffic from road to rail by 2020.

Electrification is the answer

The de-carbonisation of the EU’s electricity supply is targeted for 2050 – although how this will be achieved isn’t fully explained.

With full electrification of the rail network, rail transportation can therefore be fully decarbonised. With other transport modes, such as road and air, this is clearly not possible. Decarbonisation offers obvious opportunities for rail – but the rail sector needs to develop the capacity and ability to meet the challenge.

Some 80% of total European rail traffic already travels on electrified lines. In the UK, only 35% of the network is electrified although it carries 55% of passenger journeys. At the same time, other transport modes are becoming greener. Improving efficiency within the road sector is reducing GHG emissions and narrowing the gap with rail.

The rail sector therefore must continue to improve efficiency in order to retain its low-carbon advantage. It must also develop capacity to absorb new traffic as a result of modal shift. As Libor Lochman, executive director of the CER (Community of European Railway and Infrastructure Companies) put it: “The rail sector is in a strong position to both contribute to, and benefit from, the decarbonisation of transport.”

To ensure maximum benefit it must:

  • »  Actively support EU transport policy goals;
  • »  Set targets in electrification and high speed lines to accommodate growth and modal shift;
  • »  Make further improvements to retain advantages over other transport modes;
  • »  Articulate and communicate its case – publicising the low carbon strengths of rail and use marketing to make rail more attractive.

In order to persuade car users to leave their cars behind, the rail sector needs faster services, more comfort, less crowding and lower fares. And how about easy parking and reduced parking charges at stations? Not least, the trains and infrastructure need to be reliable and efficient.

Urban rail

Ian Walmsley is engineering development manager for Porterbrook. He also examined what he sees as the biggest opportunity for rail, namely the reduction of urban road congestion by means of trams and metro systems. The CO2 figures certainly stack up. In terms of CO2 grammes per passenger kilometre, the figures he presented were as follows:

  • »  Car – 151
  • »  National Rail – 65.1
  • »  Tram – 80.9
  • »  London Underground – 83.3
  • »  Coach – 36

Importantly, these figures have to be adjusted for load factor effect. Many trains, for instance, could accept more passengers. Service increases would be targeted at reducing road traffic where it is least efficient. With a high load factor, rail can achieve 50g/passenger.km, giving a modal transfer saving from private cars to rail of 100g/ passenger.km. According to Ian Walmsley, the rail sector needs to assert its carbon credentials, actively promote modal transfer and plan for double the number of passengers.

New technology

So in what ways can rail become more efficient in terms of energy usage and reduction of GHG emissions? In his opening address, Professor Richard Parry-Jones, Network Rail chairman, outlined them. Longer and more frequent trains with greater reliability would clearly be a help. Technical  advances will contribute too, such as intelligent traffic control, driver advisory systems (as recently introduced by First Great Western), lighter train body shells and optimised regenerative braking. Aerodynamics too will be given greater attention in train design.

Saving energy, and therefore GHG emissions, in these ways will present interesting challenges to engineers, but there is an opposing view. It was outlined by Iain Flynn, lead sponsor train systems and upgrades, strategy and service development, London Underground (LU). As he put it, “There is an inconvenient truth. No matter how we cut the numbers, delivering more capacity is the key priority. This means greater energy consumption – mostly it makes sense to run our trains flat out.”

On London Underground, energy consumption is 80-90% for traction. “Lighter trains don’t help much either,” said Ian. LU’s electric trains are already remarkably efficient, although the need for air conditioning makes the energy situation worse. Here, the real issues are modal shift and economic growth that LU’s services facilitate.

Year on year, LU needs ever more capacity, which means more energy. What goes in tends not to come out, so the net effect is that the deep tunnels are heating up. Only the Victoria Line and Jubilee Line Extension have numerous ventilation shafts. Standard upgrades put 25-45% more energy in to give more capacity, resulting in a 2-3°C rise in tunnel temperature. According to Iain Flynn, the cost of removing this heat is three times the cost of the original energy. There is a complex trade-off between capacity, cost of cooling and/or improved efficiency.

Regenerative braking offers the single biggest efficiency opportunity. It works best with newer trains operating on lines with no older trains, although LU is investigating this. The Victoria Line achieves a regenerative braking efficiency of about 35% of the traction energy consumption and the challenge is to get the entire LU network to this level.

Is it worth the effort?

Therein lies the rub. We’ve seen how rail has inherently green credentials and yet it must meet emission targets and save energy. And if UK rail meets its CO2 reduction target of 10% by 2030, what would that mean on the global scale?

As we saw at the start of this article, UK rail presently accounts for 0.0076% of the total world output of CO2. Ian Walmsley has pointed out that a 10% saving would equate to just 14 minutes of China’s output which amounts to 15,000 tonnes of CO2 every minute. It is widely recognised though that it is through modal shift that rail offers one of the best ways of reducing CO2 emissions. To accomplish that there needs to be an incentive in persuading people out of their cars and getting long haul freight off the roads.

Energy saving methods are well and good (some would say vital) and they are being embraced, but if the bottom line (rail fares and freight charges) become loaded as a result, that is not good. If our railways were to become more accessible, more efficient and yet less green, would that be a bad thing? Surely the overall effect would still be to the common good – an overall reduction in CO2 emissions for transportation. Perhaps road and rail should be considered together?

So does carbon matter to rwwail? The answer seems to depend on your point of view. Certainly the effects of climate change matter to rail, as we have seen recently. What if we were to turn the question around and ask, does rail matter to carbon? The answer then has to be no, but if and when the CO2 reduction targets are met, at least we’ll have an efficient, electrified railway network that costs a lot less to run. And there will be fewer cars on the road… maybe.

So what is sustainability

Sustainability. It’s the latest buzz-word in railway circles and everyone is talking about it.

But what is sustainability? Is there a definition? Or is it another word like ‘existentialism’ and ‘serendipity’ that clever people use to confuse more normal mortals?

It seems that there is indeed a definition. What’s more, Network Rail is now using sustainability as one factor when assessing tenders for contracts. So it’s important to understand what it’s all about.

Then who better to ask than Tertius Beneke, principal environment specialist for Network Rail Infrastructure Projects, what it’s all about?

Sustainability defined

“We often get asked what is sustainability or what does sustainability mean?” Tertius explained. “There is a well established definition of sustainability that was a product of a United Nations document entitled Report of the World Commission on Environment and Development: Our Common Future.”

That definition is: “Sustainable development is development that meets the needs of the present without compromising the ability of future generations to meet their own needs.”

On the face of it, that doesn’t help much. However, to simplify this information and to spread and implement the concept of sustainable development, Tertius uses a Venn diagram to explain the interdependencies of the sustainability concept.

Taken from Network Rail’s Sustainable Development Strategy 2013 – 2024, the diagram illustrates that sustainability is only achieved when economic, social and environmental aspects of a project are in balance.

“The spheres are also of equal size, an often overlooked part of the diagram,” Tertius explains further. “The purpose of this is that you cannot trade the one for the other, so rapid economic growth cannot be pursued to the detriment of the environment or to the detriment of people. The reverse is that economic development should not be sacrificed for the preservation of the environment at all costs.

“The definition also integrates the notion of intergenerational equity where we leave a world behind for our children that can support their needs in the same way that we had the opportunity to meet our own needs.”

Sustainability working group

Network Rail has embraced this definition of sustainability and has incorporated it not only into its policy and strategies, but also into how it actually does business.

To identify the main areas of sustainability to focus on, the same approach is used for environmental management systems where the activity of the organisation is reviewed and the areas of impact and opportunities are identified. These then form the starting point of developing robust measures including measurable quantitative data and qualitative discussions to track progress along the sustainability path as a company matures in delivering its sustainability goals.

The Commercial Directors Forum, chaired by David McLoughlin as part of contracts and procurement, has created a sustainability working group that involves the Network Rail supply chain with the aim of embedding sustainability into the work carried out by Infrastructure Projects. This group defined a list of sustainable procurement principles and has initiated a 5% sustainability score as part of all tender evaluations to drive the consideration of sustainability from the earliest phase of the project.

“Following the introduction of our sustainability strategy, Infrastructure Projects has developed objectives and targets to measure quantitative data on how we are performing in regards to our sustainability aims,” Tertius continued. “This takes sustainability from a misunderstood concept to right to the forefront where we and our supply chain can look at actual data and measure our performance. As expected, the targets measure a wide range of issues from opportunities for local employment, health and safety, biodiversity, waste management and financial efficiencies. These targets are reported on, reviewed and shared throughout Network Rail and our supply chain.”

To embed these targets and sustainability into the business and the wider supply chain, Network Rail will be implementing an integrated management system, including environmental, quality and health & safety, to formally track these targets and drive continuous improvement. Network Rail will also be using various other methods to assess performance such as PRISM (Performance and Registration Information Systems Management) and sustainability assessment schemes including CEEQUAL (Civil Engineering Environmental Quality Assessment and Award Scheme) and BREEAM (Building Research Establishment Environmental Assessment Method).

CEEQUAL Awards

Sustainability in civil engineering projects can be measured against the international CEEQUAL standard. CEEQUAL is an awards scheme developed by the Institute of Civil Engineers and is now in its tenth year. It is another way to show practically what sustainability means and how one can implement it on projects.

Infrastructure Projects already has a very good track record with its major programmes achieving a number of CEEQUAL awards. The Network Rail Thameslink project (TLP) has registered seven major projects and already won two Excellent Whole Project Awards for Farringdon and Blackfriars (90%-93%), three Excellent Interim Design Awards for Borough Viaduct, two awards for London Bridge (83% to 96.9%) and two Outstanding Achievement Awards for energy/carbon (Blackfriars) and ecology/biodiversity (Farringdon). The TLP is also the first programme in Network Rail to register its track & signalling project to CEEQUAL Term Contracts.

The Norton Bridge Grade Separation project has recently achieved an Excellent Interim Client and Design Award with a score of 97.4% which, at the time of writing, is the highest ever score on an interim award.

The Crossrail Programme has registered six of its major projects with CEEQUAL

World Environment Day

“However, it is not just about what we do at work that matters and it isn’t just about systems and processes,” Tertius stressed. “To really connect and drive change, the sustainability agenda process must be supported by hearts and minds. We need to engage people in issues that are not necessarily aligned to their working lives but which also touches on life outside of work.”

This year, for the first time, Network Rail celebrated world environment day to start bringing together all three of the spheres into the hearts and minds campaign.

Events were held all over the country to support the United Nations Environment Programme (UNEP) that focussed on food waste. Every area put its own interpretation on the celebration with activities ranging from volunteers handing out pamphlets to information tables and chilli-growing contests – anything to make people aware of World Environment Day and force them to think about the impact that their food buying and discarding activities have on the environment.

“Sustainability is not an intangible concept,” Tertius finished. “The main way of implementing it is to simply focus on where your business, or you as an individual, has the largest impact and the largest opportunity to improve the balance between people, pounds and the environment. Set some measurable targets and strive to improve on these, year on year.”

Nottingham renewed, refreshed and revised

Nottingham station is unusual in a couple of ways. For a start, it is comparatively new. Whilst many of Britain’s major stations were built in the middle of the nineteenth century, the current Nottingham Midland station didn’t open until 1904, which makes it Edwardian rather than Victorian.

It was known as Nottingham Midland as there were several other Nottingham stations at that time. Nottingham Victoria was opened by the Great Central Railway (GCR) in 1900, designed by Albert Edward Lambert – the same architect that the Midland Railway employed a couple of years later for their own project. Perhaps the GCR’s impressive new station shamed the Midland into rebuilding theirs? Nottingham Victoria is now the site of the Victoria Centre shopping mall.

The Great Northern Railway had a station at London Road, just at the eastern end of the current Nottingham station and now a health spa. When Nottingham Victoria opened in 1900, the Great Northern moved there and the London Road station declined. Passenger services ceased in 1944 and it finally closed as a parcels office in the 1970s.

The other oddity is that, for a station which serves London in one direction and Sheffield and Leeds in the other, it is orientated almost exactly east/west. This is all down to the triangle of tracks between Nottingham and Derby which surround Trent Junction. With lines coming in from Birmingham, and going out to Newark and the Lincolnshire coast, it is as much a cross-country station as anything else.

Be that as it may, Nottingham’s station on Carrington Street is overcrowded for passengers and complicated to use for train operators. Too many tracks cross or interfere with each other to make for efficient operation, and this causes delays and restricts the timetable.

A recent overview

Nottingham currently has six platforms which run parallel to Station Street. An earlier station building was accessed from this street, hence the name, before the 1904 building moved the entrance around the corner and onto the Carrington Street overbridge.

The northernmost platform is an island. Platforms 1 and 3 are the two through faces and there is an eastern- facing bay platform which is used by train services to Skegness, Newark and Boston.

DSC_5400 [online]

The second, central island forms platforms 4 and 5, and there are two through roads between 3 and 4.

Platform 6 is the northern face of the southern island. The platforms are quite long and are split into A and B zones. However, the track layout means that departing trains often have to cross other lines and that two trains cannot leave at the same time as they will foul each other.

The station building runs across the western ends of the platforms on the Carrington Street bridge. It consists of three major areas.

Fronting the street is the porte-cochère, or ‘coach gate’. This is a high- roofed area with four entrances, two on Carrington Street and one at each end, where carriages, hansom cabs and latterly taxis could drop off passengers in the dry. The glass roof allowed a lot of light into this space.

From the porte-cochère, passengers would move into the concourse, a smaller area which included the ticket office and more open space. Both of these were constructed in a mixture of red brick and terracotta tile in a flamboyant style.

Beyond the concourse is the wooden dispersal bridge, giving access to the three island platforms. Partway down those platforms is a second footbridge which not only interconnects them but is also a public right of way across the station footprint. This walkway was moved from a third footbridge, even further down the platforms, which was demolished in the 1990s.

Just south of the main station buildings is a brick ‘house’ which is the British Transport Police (BTP) building. Further along Queen’s Road,
on the south side of the station, there was rough open-air parking outside what had been the Red Star Parcels office.

The trams are coming

The last hundred years has taken its toll on the building. Although it was cleaned several years ago, the acid wash had left marks on the terracotta tiles and there were buddleia growing on the roof.
In addition, the trackwork through the station and the nearby Mansfield Junction to the west did not make for easy operation.

Nottingham City Council introduced a tram network to the city in 2004. NET (Nottingham Express Transit) operates one line from Hucknall and Phoenix Park to the north-west of the city, through the centre, to Station Street. The tram terminus is on the opposite side of the road to the station and a footbridge connected the two.

Plans were drawn up for a second phase of the tram network as early as 2006. Funding was approved in 2009 and work started in 2011.

The new plans would extend the line southwards, over Nottingham Midland station and out to Clifton and Toton. The Great Central Railway had also run over the Midland station on a 170 foot long bowstring bridge which was removed in the 1980s. However, it offered the perfect alignment for the second phase of Nottingham tram.

So a new bridge had to go in over the top of Nottingham station (not Nottingham Midland any more as it’s the only one left). The tram stop would then be moved from its site on the north side of Station Street to the middle of the new bridge, right over the station and linking with it to form a transport hub. There was no point in doing that without reworking and remodelling the station buildings to accommodate the extra traffic, and while that was going on it made sense to modify the track layout and make the whole thing more user-friendly.

Three projects in one

Plans were drawn up for three separate packages of work all interlinked into one overall project to deliver Nottingham Hub. The three partners working together to deliver it are Network Rail, East Midlands Trains and Taylor Woodrow (Vinci Construction). Nottingham City Council is funding the tram work and the Railway Heritage Trust is also contributing.

The tram bridge was one of those three packages. A two-part bridge was built adjacent to the site and slid into place over two weekends. The first was described by Chris Parker in issue 101 (March 2013) and left the bridge suspended halfway over the station while the second half was attached to the first. When that was complete, the bridge was slid the rest of the way in April.

At the same time, Taylor Woodrow started work on the station buildings. A temporary station was built on the south side of Station Street, the first time the station had actually been on that street since 1903. The cabins used to construct the temporary ticket office were recycled ones previously used for the regeneration of Farringdon Station.

The porte-cochère was closed and is being refurbished, cleaned and completely glazed to form a new pedestrian area with enhanced levels of retail. In future, taxis will make use of a remodelled Station Street rather than enter the station buildings themselves.

DSC_5347 [online]

The existing concourse is undergoing the same restoration process and the ticket office is being relocated to a more centralised position in the refurbished concourse. The dispersal bridge remains open and can also be accessed using a protective pedestrian tunnel from the front entrance, through the worksites of the porte-cochère and the concourse.The BTP has been relocated from the building on Queens’ Road to a temporary location further down the street whilst the new southern concourse is built to connect the new multi-storey car park, Platform 6 and the dispersal bridge.

Platform changes

To increase capacity, a new platform face will be constructed by stepping Platform 4 out to one of the through roads part way along. This will create a new, shorter Platform 4, and the remaining western end of Platform 4 will be been fully glazed, were rebuilt using corrugated steel in the 1970s. This has left the platforms somewhat dark, so glazed panels will be reintroduced partway through the canopy span, adjacent to the buildings, to brighten everything up.

Most of this work has been taking place over the last few months while the station remains open. However, the new stepped Platform 4 will be constructed between 20 July and 25 August when the whole station will be completely closed for trains running westward (to Derby and London) and partially closed for eastbound trains (Newark, Lincoln, Grantham and Skegness). During this period, passengers for destinations on the Midland main line will be bussed to East Midlands Parkway.

The track layout and signalling at Nottingham station and at Mansfield Junction will be radically overhauled at the same time, but that is to be the subject of another article. (page 77)

By Monday 26 August, when Nottingham will fully reopen, the new platform 4 will be in operation as will the revised track layout, and further platform work will have been done. However, there will still be much work to do. The obvious change, so far as passengers are concerned, will occur early in 2014 when the main station buildings will reopen and the East Midland’s leading city will once again have a station of which it can be proud.

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