The way contractors design and execute planned and emergency construction work has a bearing on Network Rail’s ability to achieve its user first strategy for Control Period 6 (CP6). Andy Sloan, managing director of COWI in the UK, takes a look at how design best practice is evolving.
Network Rail’s Delivery Plan for CP6 offers a refocus on its strategic objective. ‘For too long we have been introspective and focused on engineering excellence, rather than on the service that we provide ” it states. While the safety and reliability of the railway remains paramount, Network Rail is ‘determined to be driven by what is in the best interests of passenger and freight users’.
Two years into CP6, contractors across functions are increasingly considering what positive contributions they can make to Network Rail’s mission. For many, the shift in thinking might be quite subtle, formalising what has been considered a number one focus for some time: keeping the railways open while increasing safety and reliability and reducing burden and cost.
Whether the works are planned or emergent, putting passengers and freight users first starts with collaborating on the design and keeping open lines of communication between the asset owner and its contractors.
To complete works in the quickest and most robust way, it is vital to have all major stakeholders involved in the design from an early stage. It is not enough to present a buildable solution that works on paper; it must be optimised for delivery in the field.
Those early conversations and site walk-throughs can make all the difference in determining improvements and negating challenges and risks before they arise. The approach can often lead to shortened construction programmes and possessions, which has a positive impact on Network Rail’s service by helping to keep the railway open and reducing site risk.
Designing buildability in and risk out from day one also helps to improve safety and productivity, and encourages innovation – whether digital, technical, workforce or other – to get the job done in the most efficient way.
With a 200-year age gap between the oldest and newest infrastructure on the UK’s rail network, a focus on the user means contractors need to respond rapidly with the right resources and skills from the get-go.
Diversity in thought and experience is key here and can be achieved in myriad ways. Whether that’s upskilling junior engineers through varied project exposure, championing women in engineering or forming strong relationships with key stakeholders to share expertise across company lines.
Equally important is being able to leverage that diversity to approach a project through different lenses to bring it together in a cohesive and timely way. When a complex geotechnical problem is costing thousands of pounds in delays every day, the speed and slickness of the response will always have a bearing on the impact for the rail user.
An approach for an outstanding outcome
An example of these tenets in practice was the outstanding outcome for the Auldgirth landslip. In February 2020, a 40 metre long section of embankment on the Glasgow South Western Line suffered damage during one of the worst storms of the century.
The incident resulted in immediate closure of both lines with a replacement bus service for passengers, and freight diverted. As part of AmcoGiffen’s team and as a regular responder to emergency events, COWI was commissioned as designer to help remedy the disruption. The solution had to not only address the engineering challenges and environmental impact posed by the failure, but also the remoteness of the site, the steep terrain, proximity to the swollen river and inclement weather.
The response team, including Network Rail, AmcoGiffen and COWI, along with the local Fishery Board and the Scottish Environment Protection Agency, came together to discuss potential solutions and agree objectives.
The team worked collaboratively to develop several options that were in-keeping with the urgent timeframe, met the requirements of all parties and provided a robust long-term solution. This approach, combined with the close working relationships of those involved, was key to success.
The eventual solution was simple in concept and well thought out for constructability: comprising excavation of the failed embankment material and replacement with rock fill, with the lower section reinstated using rock armour to provide future scour protection. With limited room to manoeuvre, a critical aspect of the design was how to manage the flow of materials and plant onsite to reduce bottlenecks and avoid schedule delays.
While the initial closure was scheduled for four weeks, the team’s combined experience, close collaboration and meticulous planning enabled the works to be successfully completed ahead of schedule, while improving resilience for the future.
Works to stabilise Holme Tunnel were led by AmcoGiffen with COWI producing the design
Another cornerstone of improving outcomes for railway users while keeping the railway open is that of progressive assurance. When collaborating on a project, it’s much easier if there are no surprises when it comes to the solution. Designs should bring confidence, as well as safety and efficiency.
To that end, it is becoming more common to run a live design process in which the solution gains consensus from the project team – the client, the contractors, the stakeholders – before it is subject to the meticulous approval process.
The works to stabilise Holme Tunnel – a 250m long masonry arch tunnel built in the 1840s – are a fine example of how progressive assurance can improve project outcomes in this way. COWI’s involvement with the tunnel stretches back to 1997 when it was first commissioned to investigate distortion and deterioration.
By 2012, Network Rail decided to have the tunnel relined, appointing AmcoGiffen to undertake the works and COWI to produce the design, drawing on its previous geotechnical and tunnel analysis work.
The process of progressive assurance was particularly important due to the complex assessment and analysis necessary to establish the root cause of the apparent tunnel distortion and the resultant stabilisation and relining solution. The team developed an innovative design of steel hinged tunnel supporting arches requiring 400 tonnes of steelwork and 2,400 tonnes of fibre reinforced concrete.
A specialist rig was developed to allow safe remote installation of the hinged arches. Given the unique elements of the design solution, it was developed and tested using 4D animated construction sequencing, which was also used for staff training. Throughout the process, design workshops and meetings were held to openly discuss challenges which enabled an effective design approval process, creating buy-in for this unusual project.
Once the first few arches were installed, the project team reviewed their progress and refined their methodology. Tilt meters were installed to monitor movement, allowing increased daily productivity. This fine tuning, made possible by the team’s collective confidence and buy-in, significantly reduced the schedule from 23 to 13 weeks.
AmcoGiffen operations director Dave Thomas said: ‘Holme Tunnel sat on the too-hard-to-do pile for many years, maybe because everyone was looking for a standard civil engineering intervention.
‘AmcoGiffen decided to go back to their heritage roots and revive an old mining technique called back ripping. Historically, this technique was used to enlarge mine roadways suffering from distress and overloading by carefully removing the old support in increments and replacing the existing with a new more substantial support.
‘These same principles were applied to Holme Tunnel, which was successfully delivered by longstanding staff, all mining engineers in an earlier life. The operatives at the coal face were all former miners who had honed their skills in some of the toughest engineering locations you could imagine.
‘It was an incredible success and most importantly delivered safely, which the project team are particularly proud of.’
Starting with the outcome in mind
The industry is constantly being challenged to remove boots from ballast, reduce nighttime possessions and shorten work schedules. It is also constantly challenging itself to bring forth the latest innovations – whether it’s less invasive strategic asset health monitoring techniques, composite bridge designs that can be installed in a day, or low disruption tunnel renewals that can cut schedules by half.
With Network Rail’s renewed focus on the user, the rail industry has a fresh opportunity to consolidate these various objectives and find ways to solve them in tandem. For the most impactful results, we cannot work in a vacuum. Instead, project stakeholders should work together to achieve the outcomes in mind cohesively – be it reducing project risk or embodied carbon, improving reliability and asset operation and maintenance or delivering greater project cost efficiency.
By collaborating closely with our contractor colleagues and Network Rail stakeholders, we stand to gain new insights and more efficient and safer ways of working all while offering better outcomes in the process.