The successful conclusion of a 12-day blockade of the eastern section of London Underground’s Central Line is set to pave the way for future working. NCE reports.
You have to delve back to March 2006 for the last time London Underground (LUL) had a proper blockade of one of its busy commuter lines.
Back then it was Tube contractor Metronet and its subcontractor Balfour Beatty who embarked on a five-month closure of the Waterloo & City Line, during which time track and signalling equipment was completely ripped out and replaced.
Metronet’s fellow PPP Infraco Tube Lines sought a similar approach, but ultimately a 100-hour closure of the Northern Line over Easter that same year was the best it got.
Since then much has changed on the Underground. The PPP under which contractors financed and managed upgrade work for a performance based fee is gone. Metronet has been disbanded and its engineers and operatives swallowed up by LUL. Tube Lines exists, but as LUL’s wholly owned subsidiary.
And now, with the integration of PPP Infracos back into LUL complete and bedded in, blockades are back on the agenda. After all, with nighttime engineering hours on the Tube so limited, they remain by far the most efficient way to get work done.
Last month, the first blockade under the new regime was completed on the Hainault Loop, at the eastern end of the Central Line. The loop branches off at Leytonstone and serves 11 stations before rejoining it further north at Woodford.
“The Hainault blockade is an excellent example of more work being done with less overall disruption which means we can do it more efficiently”
George McInulty, LUL
But limiting the inconvenience to the travelling public is a major issue, and with LUL directly in control of work, it now feels better able to manage that.
“Blockade working is a key element of the LUL closure strategy,” explains LUL infrastructure programme director George McInulty. “There are times when the pieces of work required for upgrading assets can be parcelled together in a coherent way that makes sense to all, including our customers who have to endure the pain of railway disruption.
“The Hainault blockade is an excellent example of more work being done with less overall disruption which means we can do it more efficiently,” he says. “It’s
a great overall win-win.”
Perhaps ironically, the last contractor to carry out a blockade under the PPP was also the first to do one in the new regime - Balfour Beatty, or more correctly, Track Partnership, the strategic alliance between LUL and Balfour Beatty Rail.
And it went well. Engineering asset upgrades required at the east of the Central Line on the Hainault Loop were blitzed in the one blockade to complete 19 days of work in just one 12-day closure.
This efficient way of working will directly translate into £4M of savings for LUL. It also significantly reduced the number of hours of disruption - just 288 hours rather than the 488 it would have taken using multiple traditional weekend closures.
Building Information Modelling was used in the planning stage to identify potential programme clashes - helping to achieve the completion of 60,000 man hours without a single accident.
The 4D model was created with help from Balfour Beatty subsidiary Parsons Brinckerhoff and combined with a voice over description by delivery engineers which also served to brief workers on site.
This briefing method created a consistent statement to all operatives throughout the duration of the works, clearly setting out the scope of works, plant and material movements and safety requirements.
“It’s an exciting new method of planning, checking and implementing works, highlighting plant movement and logistical clashes in the office, and so reducing the amount of re-planning required and time lost on site,” enthuses Track Partnership business improvement engineer Ben Mills.
The original scope of works delivered during the blockade included the installation of 11 completely new sets of points in this very complex junction area and the renewal of 505m of track through the Hainault platforms including track, sleepers and ballast replacement.
Work also included 340m of re-railing works between Wanstead and Leytonstone and track reconditioning work and maintenance tamping between Newbury Park and Leytonstone. Improvements were also made to the track condition at Newbury Park where the Central line comes out of a tunnel and the rails pass from a concrete bed to ballast-based track.
Two bridge waterproofing schemes were also carried out, and 319m of drainage was installed including 10 new catch pits to prevent track flooding and signal failures. Six hundred and fifty metres of embankment stabilisation was carried out along with vegetation clearance.
Point layouts were installed in concrete bearers around Hainault station - a first for London Underground.
These will bring increased stability and ride quality over the more traditional timber bearer installation.
They also bring a reduction in wear and fixing movement and eliminate the rot typical in timber bearers, as well as reducing the carbon emissions over their lifespan compared to timber.
The longer lifespan of concrete bearers also means reduced maintenance and replacement requirements, leading overall to a safer, less expensive and more reliable track system.
A satellite yard was created near Fairlop station to cut out disruption caused by transporting material from the Track Partnership depot at Ruislip, at the west of the Central Line.
“The use of 3D dozing techniques and total station survey ensured high degrees of consistency and engineering excellence”
Jonathan Wright, Track Partnership
This enabled engineering trains to be unloaded and reloaded before travelling around the Loop to re-enter the possession.
Bulk materials were stockpiled, with two long reach grab loaders to offload spoil and scrap from engineering trains and load new material and supplies for the site.
Four engineering trains were timetabled into the traffic paths on a merry-go-round-system throughout the blockade to allow systematic and predictable logistics.
To de-risk the delivery, assembly of 37 points and crossings (P&Cs) and track panel layouts took place in the Fairlop satellite yard.
This method removed the construction from the critical path, allowing consecutive activities on site increasing the quality and safety of the construction of the panel units.
In total, 57 trains, 14 PEM/LEM units, eight road-rail vehicles, three dumpers and two tampers were used throughout the blockade.
Other unexpected issues overcome during the blockade included high wind levels leading to crane inactivity.
New Surelock point motors were fitted to the 11 new P&C layouts for improved reliability of the service. These new motors are quicker and lighter to install and have simpler and faster maintenance regimes than the existing electro-hydraulic operating mechanisms.
The blockade was commissioned and handed back safely and ahead of time, and the assets were put back into service with zero operational faults.
Track Partnership senior permanent way engineer Jonathan Wright notes that while the project delivered on cost, programme and safety, quality was not compromised.
“The use of 3D dozing techniques and total station survey ensured high degrees of consistency and engineering excellence, which will be reflected in improved track quality andreduced long-term maintenance,” he says.
These works are part of a programme of renewal works on the Central Line, which was last upgraded in the 1990s. It also includes refreshing the fleet of 85 trains and renewing track to give customers a smoother journey.
The Central Line is used by 900,000 passengers each day and the works affected around 7,500 of those customers each weekday.