Doesn’t time fly! It’s about nine months since we last updated readers on progress for this most prestigious and complex of projects – Thameslink. The last article focused on London Bridge station, the demolition of the old shed roof, the reconfiguration of platforms and the construction of the new concourse. It also highlighted the complexity of building a new viaduct over Borough High Street and the Victorian market place, providing a new pathway to the completely revamped Blackfriars station that now majestically spans across the river Thames.
The viaduct has recently won the prestigious British Construction Industry Awards “Best Practice” Award. It was designed by Atkins in association with architect Jestico & Whiles and the principal contractor for the work was Skanska UK.
During 2004 and 2006, amidst the HS1 work at St Pancras, two single bore tunnels were constructed for Thameslink.
They are known as the Canal Tunnels and they connect the Midland main line at St Pancras International with the East Coast main line just north of London King’s Cross. Over recent months there was an announcement that new track has been placed throughout the tunnels by Carillion and overhead 25kv catenary power supply is currently being installed by Balfour Beatty. Carillion is also installing slab track and associated emergency walkways throughout the tunnels.
At about the same time, the first batch of Class 377 trains has entered service. These trains, configured as 8-car and 12-car units, are now running between Bedford and Brighton. The trains are provided by Bombardier and they will allow some of the Class 319 trains to be refurbished whilst waiting for the new Siemens-built trains to be introduced in 2015 and beyond.
With so much happening, it was time to visit Thameslink’s Chris Binns, Network Rail’s head of engineering for the Thameslink programme, to find out about the current challenges. Chris, who has been associated with the Thameslink project since 2008, was only too pleased to discuss recent progress.
The team has produced detailed staging diagrams which cover all the work throughout the whole period from 2013 up to 2018. These go through ten key integrated station and track remodelling stages underpinned by large folders of charts showing staging sequences and diagrams, covering each event down to the hour. A minimum 14-day buffer has been built into each critical stage of the programme. Chris was very pleased to announce that to date, everything was happening in accordance with the programme.
The no “man-marking” approach adopted by the project is standing the test of time, demonstrating that the most suitable person for the job is appointed, irrespective of their employer. It is an approach that Chris feels is essential for ensuring that the project will be delivered on time and to budget.
London Bridge station
The old train-shed roof has now been completely demolished, exposing the Shard’s sheer walls of glass. Reflections of clouds and crane jibs mirror the adjacent sky lines.
The entrance to the station is now covered by a light, functional, flat roof structure. Borough Market viaduct melds into the urban array of Victorian buildings as though it has always been there. However, it still awaits its raison d’être, that is to carry track and eventually trains.
The architect for London Bridge station itself is Grimshaw. Their remit has been to convert the existing split level, highly congested station with its six through platforms and nine terminating platforms, into one single level station with nine through platforms and six terminating platforms – all linked together by an open concourse offering lift and escalator access to every platform. The plan is for platforms 4 and 5 to be dedicated to Thameslink and the new proposed track layout is designed accordingly.
To achieve this vision, Network Rail decided to go underground amongst the maze of Dickensian arches to construct the new concourse – starting from the south and working though to the north of the station along the line of the existing footbridge. Costain has been appointed as the principal contractor for the station work by Network Rail, supported by WSP and Hyder for the design work and, so far, platforms 14, 15 and 16 have been closed and demolished by sub-contractor, Keltbray.
The old arches have also been demolished and three viaduct spans of steel beams, each 24 metres long, are now in place ready to receive precast concrete units that will span the new concourse and support the new platforms 14 and 15. Some areas have an additional fourth infill span of between 6 and 15 metres. This section of work is well underway and programmed to be completed by March 2014. Track will then be re-connected and the platforms will become operational. After this, adjacent platforms 13 and12 will be taken out of service, the arches demolished and similar structures will be constructed to accommodate the new platforms, extending northwards.
Between the terminating platforms and the through platforms there is a two metre difference in level so a new retaining wall will be constructed and the access to the concourse work will switch from the south to the north of the station with the intention of handing over the southern portion of the
newly constructed concourse to operational use. Bachy Soletanche piling contractors have already started work in the north area, preparing the foundations for the construction of the viaducts to support the new through platforms over the concourse area.
When the construction is complete, each platform will be protected from the elements by a simple canopy structure. Where the canopies cross the concourse, a structure with northern light glazing will span between the canopies, thus ensuring that the concourse area is light as well as weather proof.
Removing old bridge decks
Meanwhile, a contract has been awarded to Skanska UK to strengthen 33 bridge decks which currently carry the rails and baseplates on longitudinal timbers. This configuration is usually a nightmare to maintain and forms an immovable object when it comes to slewing the tracks, an essential requirement of the project both to the east and the west of the station. This reconstruction work is now well underway as is piling work to the west of the station in preparation for the new through lines from platforms 6 to 9 that will provide a pathway onto the new Borough Market viaduct.
In conjunction with this work, Balfour Beatty has been installing significant lengths of plain line track as well as S&C units. To date, six new S&C elements have been laid in with around 340 metres of associated track, as well as 1,430 metres of new plain line track.
Chris emphasised the important point that the Thameslink project has not got a remit to improve the whole infrastructure. Its role is confined to the pathway allocated for Thameslink services. No doubt, the local track maintenance team would like to have all longitudinal bridges reconstructed and probably a few more miles of track relayed but in reality, that is not how it works.
Of course there is a significant amount of associated signalling work which is being carried out by Siemens Rail Automation as well as power supply upgrade work being carried out by UK Power Network Services. This is mainly associated with the DC
routes; remodelling transformers and rectifiers to ensure that they are capable of responding to the power demands of the new train frequency.
Once the main trackwork is complete, the frequency of the trains will initially be up to 20 trains per hour in the core area (Blackfriars to St Pancras). However, when the new Siemens trains are introduced, they will have Automatic Train Operation (ATO) integrated into the train design. This will be the first application of ATO on the main line although it does feature on LU lines such as the Victoria and Jubilee line.
The intention will be for drivers to select ATO through the four mile corridor through central London. This will then control the train’s movements, releasing the driver to concentrate on the passenger/ train interface. This can be quite a challenge when dealing with 12-car sets.
The added benefit of ATO will be accurate, controlled regulation of trains through this central area of the system and will mean that the frequency of trains can be increased from 20 to 24 per hour by 2018.
There is one more very important element of this project that hasn’t yet been mentioned, and that is the proposed construction of a new structure known as the Bermondsey ‘diveunder’`. Last December, Skanska UK was awarded a contract worth up to £60 million by Network Rail for the design and construction of the Bermondsey diveunder plus associated structure strengthening works. As Chris pointed out, this contract is a crucial component of the final phase of the £6.5 billion Thameslink programme.
The diveunder will create a major grade-separated junction on the eastern approach to London Bridge station. This will allow, for the first time, Thameslink lines to cross the Kent lines unimpeded on their approach to the station. It will also help to increase the number of trains which can serve London Bridge station. The diveunder will be formed from a series of new structures constructed along the line of existing operational railway viaducts. The intention is to reuse existing structures wherever possible to reduce disruption and waste; sustainability at work no less.
The track layout to the west will also be reconfigured to ensure that Thameslink trains will be able to travel round into Blackfriars station without conflicting with other train movements. Preliminary enabling work has already started on this critical piece of infrastructure.
Talking of critical, there was mention earlier of the new twin bored Canal Tunnels that will link the Midland main line with the East Coast main line. Chris explained that one of the million and one things that they have to consider is the potential for this new link to upset the power supplies of the two main line routes. As a consequence, detailed electrical testing has been carried out to ensure that voltage and current outputs would not be affected by the linkage created by the tunnels. The tests conducted confirmed that there would not be a problem and Chris was able to sign a letter permitting the rails to be connected.
This is a good reminder that the devil is in the detail and the consequences of getting it wrong don’t bear thinking about. Chris and his team have quite a challenging job: a job that, clearly, they are doing very well.