Record 125mph Sandy handback honoured
S&C Alliance wins the Infrastructure Achievement award for use of ground-breaking Parallel Dynamic Track Stabilisation technology. RICHARD CLINNICK reports
Aworld first was achieved at Sandy on the East Coast Main Line earlier this year, when the railway was reopened at its full 125mph line speed straight after renewing three crossovers and a turnout.
Such is the importance of this scheme, it has been recognised as the winner of
RAIL’s National Rail Awards Infrastructure Achievement category. The S&C North Alliance, which completed the project, collected the award at the Rail ‘Oscars’ at London’s Grosvenor House Hotel on September 21.
The Alliance comprises AmeySersa and Network Rail, and was established in 2014. Within its first year, it had increased the average handback speed after switches and crossings (S&C) renewals from 50mph to 80mph. It delivered the UK’s first 90mph handback at Craigentinny, near Edinburgh, and since its Scottish success had been looking at increasing the speeds still further.
In September last year, it made UK rail history by reopening the ECML at Belford, immediately after renewing S&C, at 125mph. That was following a single S&C turnout.
Fast forward four months and the Alliance expanded on those techniques for the February project, which was a much more technically complex track layout. Over two core weekends, one turnout and three crossovers needed renewing. There was added complexity in that there were long through bearers of the crossover layout extended under both tracks.
The project was achieved through the use of innovative techniques, deploying new technology and pursuing a relentless focus on right-first-time quality. This enabled the team to make high-speed handbacks the normal practice. It was also financially beneficial for the railway as it saved more than £ 700,000 in Schedule 8 compensation payments.
Until recently, a 50mph temporary speed restriction was the accepted practice following engineering work where trains would travel over freshly-laid track. This was needed until ballast settled and formed a strong foundation.
At the Sandy renewal, the railway was booked to reopen at 50mph after two core weekends, but the Alliance team set about attempting to hand it back at its full line speed which would reduce the disruption caused by the work.
The Alliance says that the key to delivering higher speed handbacks is accuracy and getting each step in the installation of the track right first time.
“The difference between handing back with a temporary speed restriction and reopening at full speed comes down to working within much narrower tolerances and ensuring that ballast is consolidated effectively before the line is reopened, rather than allowing the ballast to settle under normal traffic,” it says.
Every step of the process was reviewed in detail to work out how to achieve the tolerances required. Incremental improvements were achieved from the Belford
scheme and these were replicated at Sandy where possible, with improvements acted upon.
A robust, progressive assurance process that measured and signed off every stage of the construction process throughout the two core weekends was implemented and this built the evidence file critical for the handback engineer to be able to assess the line as fit for reopening at 125mph on each occasion.
Collaboration was a key part of the process too. The team worked with NR’s Infrastructure Project (IP) Track Central Engineering and Delivery team, who developed and supported trials of the advanced technology used to ensure the processes were effective.
In order to reopen at 125mph, 3D dozing was used while excavating to formation level and placing the bottom ballast to within an agreed tolerance of its absolute design co- ordinates. This is a more effective and precise way of excavating, the Alliance says, because it saves the tamper from undertaking large alignment shifts which can undo the consolidation of the bottom ballast. Production wastes are minimised, resulting in less spoil, less ballast and fewer ballast wagons used.
The Alliance deployed a Variomatic Bomag roller to uniformly compact the bottom ballast. The Bomag provides an objective measure of the load bear ability (stiffness) of the track bed – a quality control measure that has previously been unavailable.
A world first was the use of Parallel Dynamic Track Stabilisation (DTS). After the successful use of combined DTS tamping on a single turnout, two 09 4×4/4S Dynamic Tampers were used in parallel during the Sandy scheme. They worked simultaneously to lift the crossover rails at the through bearers on both sites of the crossover in parallel. The Alliance says this was essential to ensuring track quality, and mitigated the risk of leaving the bearers unsupported or distorted by the uneven movement. This process bedded in the track and ballast without the usual traffic settling period and by applying forces equivalent to 200 high speed trains passing over the tracks consecutively.
The Alliance also carried out full welding and stressing of the track for the line speed within each core weekend. The team handed back the Fast Lines at their 125mph line speed immediately after the engineering was completed. The Slow Lines were handed back at speeds of 70mph and 80mph.
In total, the team delivered seven point ends, one points conversion and one abandonment, installation of four new location boxes, one UTX and 320 metres of cable route, completed 155 welds and five stresses within the core weekend work, and 18 overhead line equipment adjustments. No injuries or delays were recorded.
Two Dynamic Tampers were used in parallel during the Sandy scheme. They worked simultaneously to lift the crossover rails at the through bearers on both sites of the crossover in parallel.