Pouring 2,670 tonnes of concrete into Waterloo station

6th October 2017

The Wessex Capacity Alliance (WCA) is responsible for an £800 million investment to provide extra capacity on services to and from London Waterloo. Most of the work is centred around Waterloo itself, with additional work at key outlying stations.

Three aspects of the upgrade project, which make a significant use of concrete, are described in outline here. When complete, they will have used nearly 2,100 tonnes of in-situ concrete and 570 tonnes of pre-cast concrete units to create the new facilities that will provide the additional passenger capacity. It is worth noting that, had it not been for an imaginative approach to the design on one of these projects, the quantity of concrete required would have been even greater.

Approach viaduct

A crucial stage in the redevelopment of Waterloo station to provide the extra capacity needed was the refurbishment of Platforms 20 to 24, the former International Terminal, which had been largely out of use since November 2007. Convertion of this part of the station for use by domestic services would need an operationally more flexible track layout on the approach to the platforms to permit up to 18 trains per hour in and out of these five platforms, compared to the six per hour capacity in the days of Eurostar.

It gets more complicated. The optimal track layout for this new service capacity and flexibility would not ‘fit’ on the approach viaduct which was installed for the introduction of the international services. It is a very carefully considered series of structures, which threaded the new international tracks above busy streets, over the existing Waterloo masonry arches and with piled foundations avoiding London Underground infrastructure and many utility services.

Mott MacDonald, one of the design consultants for the structural aspects of the work at Waterloo, had been the independent checker of the original terminal in 1992. This was to prove very useful in developing the alterations needed to the approach viaduct.

The existing viaduct arrangement consisted of three separate parallel decks with gaps between them. The original proposal was to construct two further, structurally independent, decks to infill the gaps and provide continuity for carrying the new track layout. These additional decks would have required a further 65 piles to carry them, the piling itself being an immensely complex part of the whole work, having to take place with only five metres of headroom under the existing viaduct, needing to avoid many services and requiring disruptive road closures.

Some thorough value engineering generated an ingenious alternative proposal. Could infill decking be designed such that it would act integrally with the existing decking? If it could be shown that this was feasible structurally, then there would be no need for the new piles, which would generate a significant saving in time, construction risk and cost.

Some further slight modifications were made to the proposed track layout in order to minimise the longitudinal extent of deck infills needed. Many different loading combinations were analysed to confirm the design. It was found that, under certain combinations, the existing bearings would be overstressed, or unsuitable in other ways, for their new loading conditions, so would have to be replaced.

Confirmation that the existing substructure of piles, pile caps and leaf piers could take the new loading patterns was also established. Soil investigation and pile loading test results from the original work in the early 1990s were invaluable in completing an assessment of the substructure’s capacity. Even with that information, it was essential to carry out accurate modelling of the soil-structure interaction to confirm that the reuse of the existing substructure was feasible with the new loading conditions.

Having confirmed that this was possible, the design for the new arrangement consisted of the partial demolition of the edges of the existing viaduct slabs, the modification of the structural articulation, and the casting of new in-situ concrete infill slabs to join the existing decks.

The connection between the new and the existing decking, by reinforcement bar lapping, was designed to minimise the amount of edge demolition required. The design for the new decking infills and for the bearings both required complex finite element analyses. These had to consider many different loading situations, according to the position of the live train loads, for which four different situations were analysed with associated vertical and horizontal loads (traction, braking, centrifugal and nosing) in addition to all the usual structural load parameters to be considered.

Two hydro robots were used for exposing the reinforcement in the areas where the lapping was to be carried out. 1,050 tonnes of C40/50 concrete was used for the infill slabs, with a CIIIA mix with shrinkage reducing admixture, to reduce the risk of cracks in the dry joints.

The collaborative approach to this work between the Wessex Capacity Alliance partners produced a very effective solution to the modification of the approach viaduct with estimated savings of 17 weeks in the construction period, 1,480 tonnes of CO2 and £5 million in cost. This work was completed during 2016 in preparation for the temporary use of Platforms 20 to 24 during the major closure of the other side of the station in August 2017.

Platform rebuilding and extension

Rebuilding and extension works to provide capacity for 10-car trains on Platforms 1 to 8 at Waterloo was completed this August. This work had to be achieved in a very intensive construction period during the recent 24 day closure of the whole east side of the station.
There were six key elements for the success of this whirlwind installation:

The use of pre-cast concrete units to the fullest extent possible;
Specification of rapid hardening concrete for the platform wall foundations;
In-situ concrete placement by pumping;
Delivery of pre-cast units by rail;
Placement of platform units by Road-Rail Vehicles (RRVs);
The use of sacrificial shuttering for the platform reinforced concrete slab decking.

A total of 161 pre-cast ‘C’ section platform wall units, manufactured from C45/55 concrete and each 2.5 metres in length, weighing 2.2 tonnes and with an associated over-sail unit weighing 1.1 tonnes, were delivered to the site by engineering train and unloaded and positioned using RRVs.

To permit the various stages of the work to follow one another as closely as possible, a rapid hardening C32/40 concrete specification was used for the wall foundations, with a required strength of 20MPa gained in only two hours. The 140 tonnes of in-situ concrete for the foundations was all placed by pumping, up to 75 metres distance, from a delivery point just outside the station.

Kingspan sacrificial shuttering units were used to form the new platform decking and, all the in-situ concrete, another 750 tonnes of C32/40 specification, was again pumped to create the mesh-reinforced slabs.

New lift shaft at Vauxhall station

Vauxhall station is the first station after leaving Waterloo and has four island platforms built atop a long masonry arch viaduct.

Congestion relief on Platforms 7 and 8 is needed and the WCA is constructing an additional set of stairs at the country end of these platforms. To accommodate these stairs it is necessary to relocate the lift shaft.

The existing station viaduct structure relies on continuity and buttressing for structural stability. The horizontal thrust at the spring line from one arch is balanced by forces from the adjacent arches.

Works to Platforms 7 and 8 necessitated breaking out a three-metre-wide section of arch to allow for the construction of the new lift shaft, which would affect the existing thrust flow. As the removed section would be small when considering the overall width of the viaduct, it is possible that the thrust would have redistributed.

However, arches are complex and difficult to analyse and the WCA designed structural elements to provide a defined and alternative thrust path to ensure that the stability of the arches was not compromised. These elements are the new in-situ reinforced concrete walls of the lift shaft and a transfer beam keyed into the pier. Strain gauges installed on the new concrete elements confirmed that the thrust was now taken through them.

The in-situ part of the lift shaft is constructed up to the level of the arch intrados. Once the three-metre length of the arch had been demolished to make way for the lift shaft, four pre-cast units were installed above the in situ work to complete the shaft. The in-situ part of the new shaft did all the arch propping and so no temporary works were needed for overall stability. The pre-cast units were made by Shay Murtagh and the work will be completed in 2018.

Generating extra capacity from Waterloo station is an enormously complex programme involving all engineering disciplines, of which concrete engineering is perhaps the least well-known but vital part of this work. 2,700 tonnes of new concrete used in the Waterloo completed approach viaduct and platform works, with more required for forthcoming Vauxhall lift shaft works, demonstrate this in no small measure.

This article was written by Mark Phillips.

What went wrong during the Waterloo station upgrades?

6th October 2017

Waterloo station at night. Credit: Daniel Gale/Shutterstock.

London Waterloo station was recently the subject of a 24-day partial blockade as significant upgrades were made to the station. Platform extensions, trackwork modifications and signalling upgrades were all undertaken as London’s busiest station underwent its first major upgrade since the arrival of Eurostar in 1994.

Scheduled to last from Saturday 5 August to Tuesday 29 August – Monday was a bank holiday – this was a major piece of work. The five organisations that make up the Wessex Capacity Alliance are well integrated and the planning and preparations had been meticulous. Nothing was left to chance.

As a result, nothing should have gone wrong. Yet it did. The full reasons won’t be known until at least two enquiries are completed, but here are some early indications.

Network Rail CEO Mark Carne during a visit to the scene. Credit: Network Rail.

Slow-speed crash

The first sign of trouble came early in the morning of Tuesday 15 August, ten days after work commenced. The 05:40 to Guildford, 10-car train made up of a combination of Class 455 and 456 units, pulled out of Platform 11 on time.

Two minutes later, having reached a speed of 11mph, it veered to the left, struck a train of empty Network Rail wagons, and came to an immediate halt. Of the 23 passengers and two employees of South West Trains that were on the train, only three were treated at the scene by paramedics and none required hospital treatment.

An early investigation by the Rail Accident Investigation Branch (RAIB) revealed that the points were misaligned and had directed the passenger train away from its intended route. The misalignment was a consequence of a temporary modification to the points’ control system.

Use of the term ‘misalignment’ indicates that the points were not set for a particular route. Furthermore, for the train to take the wrong route, the gap between the wrong route’s stock rail and point blade must have been sufficient for the wheel flange. This implies that the points were around mid-position as the train left the platform.

The question then arises why should the points be in such an abnormal position. Two possibilities are that the trailing points were incorrectly set for the incoming empty stock move into platform 11 which then burst them, leaving them in mid position, or that, for some unusual set of circumstances, the points moved mid-position after the empty stock train arrived in platform 11.

Worryingly, this was a failure of the signal interlocking’s detection system as the initial RAIB release states that the train driver and signaller received indications that the points were correctly aligned, and thus locked.

The RAIB will conduct a full investigation to identify the circumstances leading to installation of the temporary control system modification, the safety measures provided while the temporary modification was in place, the checking and testing procedures applicable to the modification and any relevant underlying management factors. Although it will take several months to publish the formal report, the serious nature of this incident is such that the lessons from this incident for ongoing signalling project work need to be understood as a matter of urgency.

One key issue is the safety measures that were in place. Had the points been clipped and secured, the accident would not have happened. However, the Rule Book does not require this as the Person in Charge of the Possession only has to confirm with the signaller which routes are to be kept closed. It will be interesting to see how the RAIB views this requirement.

Those who planned the Waterloo works clearly considered that some form of physical protection was necessary. Hence wagons were deliberately placed to protect the workforce behind them from the live railway. It was a step well taken – without them the diverted train could have ploughed into people working on the station improvements. However, had the points been clipped there would not have been a derailment.

Testing overrun

Having recovered from the delays caused by the accident, news then broke, early in the morning of Tuesday 29 August, that the engineering works had overrun. All lines were open by 07:20, but the ensuing disruption lasted all day. Word was that this overrun was due to extended signalling testing.

There were more delays, albeit short lived, on the morning of Wednesday 30 August after a track circuit failure closed Platforms 1-3. Once again, there was some residual disruption even though the fault was cleared by 07:38.

Were these faults connected to the accident two weeks earlier? In a way that’s possible – having experienced such a serious fault, the signal checkers were no doubt particularly diligent and they had also been delayed starting their job. Being the last step in the process, it’s the testers that get the blame although the problem could have been the delay caused by the accident knocking-on through the project timeline.

Signal testing is performed to make sure that there are no remaining faults before a line is returned to service. If a fault is found, that’s a good thing as it can be corrected and the travelling public isn’t put at risk. But that correction takes time, and that’s a bad thing, although it’s far better to wait and only return a line to service when it is 100 per cent safe to do so.

And the track circuit failure the following day? Unfortunately, signalling faults do occur. On the 30th there was also a signalling fault between Farnborough Main and Basingstoke, which delayed Southampton-bound trains. The day before, a points failure at Kew Bridge and another at Portsmouth Harbour caused problems and, to cap it all, a broken-down train between Leatherhead and Effingham Junction closed all lines while a failed freight train between Eastleigh and Southampton Central did the same. So the Waterloo problem could have been mere happenstance.

It could also have been another example of new work disturbing old installations and revealing or causing faults. Only a full investigation will give all the answers, and Network Rail and RAIB are undertaking theirs as this is written. However, the barrier train did its job, no one was hurt, and a massive amount of work was achieved over the course of 24 days.

This article was written by Nigel Wordsworth.

It’s all down to good planning: an interview with Network Rail’s Francis Paonessa

4th October 2017

On the face of it, Network Rail didn’t have a bad Christmas in 2014. 11,000 people were deployed to work on 2,000 sites around the country, with 314 out of 322 projects handed back on time. That’s a 97.5 per cent success rate – better than the 95 per cent that was anticipated.

So only eight projects overran.

However, and it’s a big ‘however’, two of those eight were at King’s Cross and Paddington stations.

King’s Cross was closed for an extra day, and the contingency plan to use Finsbury Park went wrong for several reasons (see issue 142, February 2015), resulting in overcrowding, confusion and exasperated passengers.

Paddington, which should have been handed back at 07:00 on 2 January, wasn’t finished until 13:14 that day. The result? More overcrowding, confusion and exasperation.

Political fall-out

Questions were asked in Parliament and Network Rail chief executive Mark Carne demanded a full report be on his desk on Monday 12 January. Wednesday 14 January, Carne and colleague Robin Gisby, who had been the director on call over the holiday period, appeared in front of the Commons Select Committee.

Then, to cap it all, Infrastructure Projects managing director Dr Francis Paonessa, the author of Mark Carne’s report, and who had only been with Network Rail for a few months, had Rail Engineer come to his office to ask what happened – the first press organisation to do so.

As it turned out, Francis was both transparent and informative. He detailed all the reasons for the overruns, explained how they happened and what mistakes had been made, and pledged to improve things for next time.

“At the end of the day, the railway is here for passengers. It’s not here to be a railway,” Francis Paonessa affirmed. “It’s here to transport people around and we must put their needs and requirements first.”

“It shouldn’t matter to the passenger how we’re making sure that they’re not disrupted, whether it’s through guaranteed delivery plans or excellent service, all that matters is that the trains run on time. We need to do what we say we will do which is to deliver an effective railway and make sure that it is there when the passengers need it. That’s our mission, that’s the mission we set out to achieve. It’s one that Mark Carne has said quite clearly that we’re not doing well enough.”

“We need to do better and we will do better.”

Waterloo woes? Or careful contingency?

And they have got better, despite the programme of engineering works at each holiday period getting bigger. While some delays have occurred, overruns have largely been on minor works and can be measured in minutes rather than hours or days.

However, the recent August bank holiday demonstrated not only how complex these programmes are, but how easily they can still go wrong. Across the country, the engineering works were the largest ever undertaken over an August bank holiday, costing £130 million and involving 17,000 staff. It included the culmination of three and a half weeks of work at London Waterloo, Britain’s busiest station, where 1,000 engineers and track staff worked 24 hours a day to deliver one of the largest and most complex upgrades at the station in a century.

Unfortunately, the work at Waterloo overran by two hours owing to safety critical work to test the signalling taking slightly longer than planned in the final hours of the programme (explained elsewhere in this issue). In itself, a two-hour overrun after 180,000 manhours of work had been carried out doesn’t sound too serious, but it affected trains and passengers throughout the day. However, communications were better, keeping passengers informed, and there was nothing like the disruption that occurred two years earlier.

External benchmarking indicates that this perceived progress is not purely subjective. Aspire Europe recently completed an independent review of 400 project companies around the world and concluded Network Rail Infrastructure Projects is in the top 10 per cent of project delivery organisations globally and is the world leader in the global transport sector.

The review highlighted a “stark improvement in performance” today compared to the systems and processes used in 2014. The report noted that “the results have demonstrated an exceptional level of improvement for a large organisation” and that, in two measures, infrastructure projects has set the new international benchmark.

Works are also being delivered more safely, with workforce injuries reduced by nearly 40 per cent in the three years to 2017.

So what has changed? Rail Engineer retraced its steps to Dr Paonessa’s office, now relocated to Euston from King’s Cross, to ask him.

Setting the scene

To understand the legacy of some of the issues, it is necessary to go back to Christmas 2007. A blockade of the West Coast main line at Rugby had been planned as part of the route modernisation programme. It was originally planned that this should be handed back after 30 December 2007, though an extra day’s extension was requested.

As it happened, the possession overran further, until 4 January 2008. The subsequent ORR’s report concluded: “there is still work to do to put adequate plans in place to handle passengers and freight affected by the possessions and to develop contingency plans.”

Whilst this bears striking similarity to comments made after Christmas 2014, Network Rail had improved its procedures in the interim. A new Delivering Work Within Possessions procedure was put in place under which every project was assessed to make sure there was at least a 90 per cent chance that it would be delivered on time. Key blockades, which could badly affect the network, had to exceed 95 per cent.

Both King’s Cross and Paddington had exceeded that 95 per cent target for completion on schedule, but they still were not returned on time. And the effects were damaging for Network Rail’s reputation.

“I think we’d all agree that having a 90 per cent success rate of our major possessions would just be completely untenable at any bank holiday, and Christmas 2014 really underpinned that,” Dr Paonessa commented. “At the same time, costs are obviously really important, so we can’t guarantee hand-back 100 per cent by being super-conservative in our delivery or we could never afford to get anything done. It’s a fine and complex balancing act.”

Therefore, the task was to maximise the work done during a blockade, without building in too much cushion, while still handing back on time.

Contingency planning

A railway is all about its passengers, as Francis had affirmed back in January 2015. So that was where he started: “We looked particularly at the operational contingency plan, which is very much route-led with the train operators. If we’re going to end up in an overrun position, what are the series of mitigations that we can put in place for the passengers?”

The idea is to have a strong contingency plan, or plans, which can be brought forward if the project gets into trouble. For example, these might be to get the Fast lines back up and running, so buying the project a bit more time to finish off the Slow lines.

The operational plan is then built up from the contingency plan, putting the interests of the passengers first rather than those of the engineers. But the aim still has to be to get all the work done on time.

“If you only ask one question, which is ‘What’s the likelihood of getting the full scope back on time?’ you tend to be very conservative in the work scope,” Dr Paonessa explained.

“Instead, we ask ourselves two questions now. ‘What’s the likelihood of getting all the work handed back?’ and ‘If we can build in some pieces of work towards the end that we could curtail, then what’s the likelihood of being able to hand all the work back?’

“By taking that approach, we can accept a lower percentage for the ‘handing it all back’ versus the ‘guaranteeing being able to hand it back’ by just structuring the way we do the work. Typically, we lose about half a per cent of the planned work in mitigations which, considering the scale of the work that we deliver, is really good.”

It seems to be working. There have been no significant overruns (excepting the two hours at Waterloo) on any bank holiday for the last two and a half years.

One truth

There has also been improved communications. The project teams report to Route Control and thence senior management and key stakeholders. From there, the communications team disseminates what is happening – when, where and, crucially, why – to the press and the public. So there is consistency and the message is accurate and timely.

As well as keeping passengers informed, this single message is crucial if there are problems to solve.

“It has made a huge difference,” Francis stated. “We can, at a very early stage, get the route control managers involved in the process. Frequently, they can facilitate the involvement of their own staff and quite often will get several operational teams to come and support hand-back activities. We’re also then fully integrated – our Route Services and Supply Chain teams sit adjacent to each other in Milton Keynes, so any knock-ons to drivers, locos, tampers can all be arranged in a very timely and consistent way.”“Importantly, my project teams aren’t making decisions on the ground that aren’t supported by the external infrastructure and backed up by project contingency plans. We have also put in place mechanisms and people outside of the project to challenge, and hence counter, the natural optimism bias that you have when you are working hard on the job.”

So now, if the project team is tempted to say: “Yes, we’re a bit behind but we’ll catch up,” there’s an external person who can ask why they think that, what plans do they have to make it happen, and what happens if the team gets to a point of no return? Project teams are no longer able to pass a key halt point, as they did at King’s Cross and Finsbury Park, without the approval of a third party.

Due to the amount of work going on, one of the big problems at Christmas and other key holiday periods is the scarcity of resources. That doesn’t just include machinery and the workers on track, it also includes the drivers of the engineering trains that keep the sites supplied.

Now, spare drivers are employed, a small price to pay compared with the cost and reputational damage caused by a major overrun.

“If you can’t move the tampers at the end of the day, if you can’t move the locos, if you start running out of drivers for resource vehicles on a work site which is totally dependent on them, you’re suddenly in big trouble,” Dr Paonessa stressed. “Now we’ve got an agreement with the freight companies that any of the drivers can drive any of the locos, so if we need to shuffle them round site, we can do that.”

Resources and access

A perennial discussion point is whether Christmas, and the other bank holidays, is the best time to do major work, or whether it would be better done throughout the year. Resources would be more available and, perhaps, the weather would be better.

“We’d like to have longer periods where things are closed down to give us full access to the railway, but we also know that the passenger disruption that this causes is really significant,” was Francis Paonessa’s response. “So we entered into CP5 with an assumption, as part of our business plan, that we would get 25 per cent more access than we did in CP4. As it turns out, I think in Year 1 we ended up with 16 per cent less.”

Less?

“Less. In year two -14 per cent less. This year I think we have 11 per cent less access than we had in CP4. And, more importantly, we’ve seen a 40 per cent reduction in 24-hour plus possessions and a 50 per cent increase in the number of less than eight-hour possessions. A great proportion of the access we have is now made up of very short periods of time – in fact our average possession that’s less than eight hours is only 5 hours and 30 minutes. So, not only has the quantity of the access changed, but the mix of it has changed significantly.”

This is an unfortunate by-product of having such a successful railway. Late trains are popular, early trains are popular, so operators are unwilling to give them up to facilitate engineering works, squeezing the time that Network Rail can get on track. Bank holidays, when on average 40 per cent fewer people travel by train, are still the obvious solution.

“There are some jobs that can only be done in three or four day blocks,” Francis added, “and they can only therefore be done at Christmas and the major bank holidays. Getting a three-day block of the West Coast at any other time of the year would be impossible.”

“However, it’s worth remembering that, on average, we’re delivering £130 million of major renewals and enhancements every week. So, whilst the bank holidays and other points in time where we tend to have the longer blocks represent a very visible peak, they are still a relatively small proportion of our total delivery in the year.”

Major projects

While Network Rail seems to have largely fixed its problems with Bank Holiday overruns, there are still other areas to improve. For example, Great Western Electrification and Sheffield Tram-Train are both running late and over budget. In contrast, projects such as the Ordsall chord in Manchester and Norton Bridge in Staffordshire are successfully being managed through alliance partnerships.

Does this mean that alliances are the way forward? Statistics show that, when Network Rail is working in alliance with its contractors, costs are being held to within 1.3 per cent of budget, but Dr Paonessa warned against jumping to conclusions.

“When you look at that, you’d say: ‘Having an alliance is a really good way of managing cost control,’ and it is, but I think it’s the wrong conclusion. Because, if you look at what is needed to be able to set up an alliance, you have to have a very clearly defined scope, you need to have worked out the options and have the opportunity to really cost it. Only then can you set up an alliance because, at that point, commercial partners will be prepared to take those commercial risks.

“So what that really says is that projects that work well are ones where we spend about twice as long in development as we do in delivery. Where we’ve seen the large cost increases tends to be when commitments in time and cost are made against very early estimates. It was one of the key things that came out of the National Audit Office report on Great Western, and very similarly on Sheffield tram-train. So, I’d say that our delivery capability is excellent when the scope and access are properly pinned down.”

That’s borne out by a study the Department for Transport undertook with University College London (UCL) last year to look at optimism bias in early GRIP (Governance for Railway Investment Projects – an eight-stage process) phases. It concluded that cost estimates made at the GRIP 1 stage (output definition) tended to be 66 per cent optimistic, 40 per cent at GRIP 2 (feasibility) and 17 per cent at GRIP 3 (option selection).

With a five-year Control Period cycle, plus two years in its preparation, some projects are being costed up to seven years before they are built, when they are still in the early GRIP stages and optimism is rife.

Post GRIP 4 (single option development), when the options are much clearer, Network Rail is working within three per cent of budget. So, it seems that the problem lies with being forced to estimate costs at an early stage of a project, which is just what happens under the current control period funding. At the start of CP5, 80 per cent of the projects hadn’t been finalised, yet they were all costed.

“It is very challenging to manage within a finite cap when you’ve got inherent levels of uncertainty built into the work that you’re doing,” Francis Paonessa commented. “You only need to reflect back on the UCL work to say that those uncertainties are very, very real.

“I think that the key point, and the bit we’ve been working with the Department to get built into the process, is what we call a ‘final investment decision’. This means that we don’t commit financially, and to delivery times, against projects until we actually know what they are and what they’re going to cost. That’s a discipline which we’d really like to see built into the next control period.

“How that gets funded is a different question, but it would certainly be recommended in our Enhancement and Improvement Programme that there is a final investment decision when we get to the end of somewhere around GRIP 3 or 4, depending on what’s appropriate for the project. Then we’ll say, ‘Right, we’ve now got a very high level of certainty, we’re about to move into a delivery phase so we’ve got much greater certainty of access as well, we know it’s going to cost this, it’s going to take this long, do you still want to buy it?”

In the recent High-Level Output Specification (HLOS) for England and Wales, the DfT has indeed noted that “the Statement does not commit to infrastructure enhancements. These are expected to be dealt with separately.” It therefore looks as though major projects won’t, in future, be part of the control period system but will be costed and timetabled individually, at the appropriate time and when all the facts are known.

Hansford Review

Last month’s Rail Engineer (issue 155, September 2017) outlined the main conclusions of the Hansford Review and included comments from its author, Professor Peter Hansford.

Although the review focussed heavily on investment, it also set out the benefits of private-sector competition for Network Rail.

In addition, the report made some practical suggestions for Network Rail to consider. These included creating a new service level agreement that establishes the terms of business between Network Rail and third parties. It also said that there should be a single point of contact within Network Rail to simplify the process.

Asked about his view of the possibility of third party investment and delivery – and, in the latter case, the competition this could bring to his organisation – Francis responded positively: “In some respects it’s difficult not having anyone to compete with as we have no benchmark to measure ourselves against and be compared with. The analogy I’ve typically used is of Usain Bolt running the 100 metres – how do we know how fast he is running without having a competitor to reference his performance?”

Safety

However a project is delivered, to budget or not, on time or late, everyone acknowledges that it has to be delivered safely. Francis was cautiously upbeat about this.

“The year before last, we managed a reduction of 26 per cent in our lost time injury frequency rate, last year another 16 per cent and this year we’re already on track to hit our target of 10 per cent.

“I personally find it very difficult to set a target that isn’t zero, in relation to injuring people. But, at the same time, you have to recognise where you are and where you’re moving to and to set challenging but realistic targets. And if you think that only five per cent or so of the labour that’s in those hours is directly controlled by Network Rail – the other 95 per cent is in our contracting community – I think you really have to recognise the large efforts that have been made by our supply chain to deliver these figures.”

“The biggest single influence on safety is planning, and we can see a very, very clear correlation in the data between safety and performance. So, at those times when we do our best planning, which tend to be the bank holidays, we’ve seen the lowest lost-time injury frequency rate, which typically can be a third to a half less than our moving annual average.”

So, as well as Christmas work now being better controlled in terms of time, budget and contingency, it’s also safer. And that’s a Christmas present we’d all want.

This article was written by Nigel Wordsworth.

Moses Gate bridge – Best laid plans

4th October 2017

Hidden by the big-bang schemes that commanded everyone’s attention through August was a routine track realignment at Moses Gate, a district to the south-east of Bolton. The job, which added another piece to the sprawling jigsaw of the Great North Rail Project, involved clearing a short section of the Manchester-Preston route for electrification and 100mph running.

The work had been planned as part of a blockade which shut the southern end of the line from Saturday 12 August to Monday 28 August (a bank holiday), the sharpest focus being on platform, track, signalling and overhead line works at Bolton station.

Don’t hold back

From Farnworth, three-quarters of a mile to the southeast, the railway passes through a cutting on its approach to Moses Gate station. Immediately before the platforms is an overbridge – replaced in 1968 – carrying the main A6053 Bolton Road and part of its junction with the A575. The structure is skewed by 55 degrees and, as a result, extends for some 35 metres.

Until recently, the wedge of land on its south (Down) side between the road and the railway had been retained by a wall 18 metres long. Beyond this, a similar length of slope was battered back and soil-nailed in 2015. Since around that time, water had been recorded coming through both the wall and adjacent bridge abutment, causing track maintenance issues. United Utilities conducted tests to determine the source; these proved inconclusive, but it was reported that no leaks could be found from the water main that crosses the bridge under the pavement on the east side.

Nevertheless, this had become enough of a problem for a remediation scheme to be pushed forward as part of the enabling works for electrification. Network Rail contracted the Buckingham Group to deliver it, the firm having previously delivered platform works at Moses Gate.

The intention was to remove the Down line, install new drainage and dig out the wet bed associated with the water ingress. Both tracks would be slewed, the Up by 100mm and the Down by 150mm to resolve a gauging issue caused by the retaining wall which, to assist further, would have its brickwork scabbled back over a distance of about five metres. At the station, the platform copings also had to be reset to follow the new track alignment.

Critical path

To ensure the stability of the retaining wall was not affected by the drainage works, excavations were limited to 300mm below sleeper level. In addition, arrangements were put in place to monitor the wall every two hours. On the first Saturday afternoon – with good progress being made – signs of movement were recorded. This became significant over a six-hour period, with the wall being pushed towards the track by 140mm. The southernmost section of bridge parapet cracked and slipped, prompting its removal to prevent any risk of it falling onto those below. But at eight o’clock that evening, the decision was taken to withdraw the workforce on safety grounds. Whilst this was the only tenable option, it came with the potential for repercussions at other sites along the line.

During the following Monday night, the blockade plan required six engineering trains to pass through Moses Gate on the Down line to service Amey Sersa S&C renewals in Bolton. Fortunately, no more movement of the retaining wall was recorded in the 24 hours after work was suspended; this allowed ballast to be tipped at the toe – thus resisting any further movement – whilst some of the brickwork defects were stitched and grouted. Thereafter, the Down line was relaid and slewed into the six-foot by 160mm in order to maintain the correct gauge. The trains passed through safely at 5mph.

By this stage, it was already clear that the retaining wall would have to be removed so the process of designing a solution got underway immediately. Plans started to emerge during Monday 14th August, led by consultants Tony Gee and Partners from their offices in Manchester and Hong Kong, an approach that ensured continuity of effort around the clock.

On the morning of Thursday 17th, the site team emailed United Utilities to express concern at the volume of water coming from the abutment. An initial requirement was to excavate material from behind its southeast corner; as part of this process, the buried services crossing the bridge had to be exposed. With the tarmac removed, progress was made using a Vac-Ex suction system. At around 16:45, a water main – passing a couple of metres from where the work was taking place – burst suddenly.

Full flow

Within half-an-hour, 140 metres of railway looked more like a canal. The influx of water from the lower part of the abutment was now considerable, whilst significant quantities were also being discharged from weep holes cored by the team through the retaining wall to relieve the pressure. As new paths were created, longitudinal fractures opened in the brick and stonework; a movement of 240mm was recorded and a large bulge developed. Mud was deposited on the track, washed out from behind the wall where a void was created.

The main road had to be closed and local residents were left without water until the early hours of the following morning. Although the supply to the main was quickly turned off, difficulties with a valve meant the flow did not fully stop until Saturday afternoon – to address this, pumping equipment had to be brought in.

Despite the depth of the inundation, the water had gone from the railway within 24 hours – testament to the efficacy of the new drainage. However it had caused the tracks to lift, meaning they would have to be re-laid before a 100mph train service could be introduced.

Now what?

The dismantling of the retaining wall continued in tandem with the excavation at the southeast corner of the bridge abutment. The team’s expectation – based on the construction drawings – was that concrete fill had been poured behind the abutment wall – a four-feet thick masonry structure – to help support the deck slab. However, it became increasingly apparent that there was no concrete: the load was largely being carried by the stonework.

Although investigations revealed the abutment’s condition elsewhere to be generally good, this discovery added a substantial new element to the design and site works – the requirement to stabilise that corner of the bridge. In all likelihood, it was this that pushed the programme beyond the blockade’s end-date of Monday 28 August, partly resulting from the need to erect a trestle – blocking the Down line – to temporarily prop the deck. Recovery from the burst water main was well in hand and could probably have been finished on time.

Moving forward

Whilst the rest of us were enjoying an uncharacteristically pleasant August Bank Holiday Monday, staff from Network Rail and Buckingham were getting to grips with the abutment reconstruction. Having dismantled a section of the masonry wall approximately four metres in length, formwork was assembled in advance of the following day’s first concrete delivery from Hanson. Once poured and cured, the process was repeated, building up in three lifts of 1.5 metres to meet the bridge deck. By the end of the week, this task was complete.

To replace the retaining wall, five precast concrete cylinders, 2.5 metres in diameter, were assembled in an excavation at the toe of the cutting slope and filled with concrete. A sixth may be installed as part of the permanent design, which is still being developed. The railway was then cleared, allowing Buckingham to restore and tamp the tracks on the new 100mph alignment.

Services between Manchester and Bolton resumed on Wednesday 6 September, albeit with a 20mph speed restriction imposed through the site. This was soon raised to 50mph, first on the Up line – on 7 September – and on the Down the following day. The tracks will need to be renewed before 100mph running can be introduced. Trains started serving Moses Gate station again on Monday 11 September after Story Contracting had attended to reinstate the copings and platform surfaces.

All together now

Work continues on site, but the immediate priority – getting passengers on the move again – has been accomplished. The water main is being diverted to the other side of the bridge, but this is complicated by the shallow depth of cover available. Partly as a result, it cannot yet be confirmed when the highway will be reopened for vehicular use. Provision for pedestrian access has been in place throughout. Obviously, the disruption impacts both on locals and those for whom the main road was regularly travelled. Ongoing dialogue with the Council ensures all parties share a common purpose; there is a clear intent to get the job done as quickly as possible.

But this is the nature of unpredictable events – they pose challenges that are rarely quick to resolve: design, procurement, logistics, manpower. All these have tested the team from Network Rail and Buckingham as an everyday task escalated first into a local difficulty, then an emergency situation. They were helped out by the staff from Story, who would otherwise have been dealing with the platform copings, and a UPAC piling team, redeployed from a site near Farnworth Tunnel. More hands make lighter work. As is so often the case, the railway really comes together when it’s up against it.

Thanks to Olivia Boland, Network Rail’s scheme project manager, for her help with this article.

Written by Graeme Bickerdike