Regular readers will be familiar with the many different individual engineering projects forming the integrated plan to totally transform the station and surrounding railway infrastructure in the Reading area. Writes Colin Carr
This £895 million project, which started in 2008, is now approaching completion. There are various bits and pieces of work still underway in the station itself, but the one significant project that will complete the aims and objectives of the scheme is the construction of a 2km railway flyover at the west end of the station.
However, let’s start by reviewing the current situation at Reading and the anticipated benefits that will be realised from the successful completion of the overall scheme. At present, more than 50,000 people use Reading Station every day and every day more than 700 trains pass through it. Passenger numbers are increasing and it is estimated that they could be double by 2030.
In addition, freight business has increased by 60% with rail freight traffic from Southampton and other ports passing through Reading and having to cross the main lines in the process. These trains can be up to 750 metres in length. As a consequence, Reading is becoming one of the busiest and most important locations in the country. It is also a train operator’s nightmare.
Improved travel experience
The Reading project can now boast a nearly- completed station that is not only designed to accommodate the anticipated increase in passengers but now also provides easy access into the station from both north and south sides of the town, thus achieving an ambition that the local community has aspired to for some time. Also, at the London end of the station, a formerly-redundant tunnel has been totally refurbished and new tracks installed – thus enabling trains to pass from the north to the south side of the station, without crossing any lines, to link up with the route to Gatwick and beyond. This is dramatically improving the travel experience for passengers travelling from the west to the southeast.
In addition, a new train depot has been built on the northwest side of the station. The depot complex is more than 2km in length and includes all the latest facilities. It was built because the existing train depot needed to be demolished to make way for the aforementioned viaduct but, before focussing on that, mention must be made of the major bridge reconstruction just west of the station as well as two new railway bridges, built to dramatically improve road facilities in the area.
So, back to the new viaduct. This will be completed in the summer although the infrastructure will be commissioned in December 2014 with trains using the main viaduct from January 2015. It will carry high speed trains (HSTs), that run on the Great Western main line (GWML), over the freight lines and straight into the station. It will also carry Cross Country trains over the freight lines independently of the HSTs, so the different train operators will be able to manoeuvre in and out of the Reading area freely and without impeding each other. This is an operating achievement that has not been addressed since Brunel built the first layout in the 1840s.
Clement Kwegyir-Afful is Network Rail’s project manager for civils work on the site. He has been connected with the construction of the viaduct from the beginning, when Network Rail appointed Atkins to design this new structure. Clement was involved with the tendering process and, in November 2012, the letting of the ICE 7th Edition construct-only contract to Balfour Beatty (the contract was later changed to an ICC Target Cost contract). The value of the work was approximately £45 million and the site start date was originally set at 7 January. However, Balfour Beatty could only start in certain areas in April after the completion of stage F, track and S&T removal. William Smith is Balfour Beatty’s Project Director.
The first requirement for building the viaduct was to stabilise the ground ready for the construction of bridge piers, box structures and culverts. Extensive lengths of sheet piling were installed to support the existing running lines and to cater for the varying levels encountered on the site. More than 1008 Continuous Flight Auger (CFA) piles, varying in diameter from 900mm to 1050mm, were also placed, some of which were adjacent to running lines. A careful programme, designed and reviewed hour-by- hour, was introduced to maximise efficiency and avoid any disruption to the railway timetable.
This worked well and the ground work was completed successfully, although there were periods of terrible weather and site flooding. Clement explained that, during these periods, it was important to inspire the entire workforce to focus on the end goal and the belief that all targets are achievable when they work together as a team, regardless of conditions.
Various innovative methods were introduced and, on occasions, the piling had to be carried out within two-metre-diameter tubes which kept the groundwater from gushing up to destabilise the piling mat.
As well as the CFA piling, an additional 1851 Vibro concrete column (VCC) piles, each six metres long and 600mm in diameter, were installed at each end of the viaduct to support the reinforced earth ramps. In total there are now 21.5km of CFA piles and 10.5km of VCC piles in the ground supporting the structure of the new viaduct.
Piers fixed and free
Atkins designed two types of bridge pier, one a fixed pier two metres wide and the other a free pier 1.2 metres wide. The fixed piers are supported on a 16 pile configuration and the free piers are supported by eight piles. The reinforced concrete fixed and free piers alternate and they are positioned 25 metres apart, ready to support seven precast concrete beams. The design requires these precast concrete beams to be fixed together longitudinally with interlocking reinforced concrete over the fixed piers, thus allowing bending moment forces to be transferred into the columns and for the beams to be freely supported on the free piers with a 60mm gap between the beams.
The beams were fabricated and supplied by Shay Murtagh and had to be transported across the Irish sea to Liverpool and then on to site by road. It was important that the beams arrived on time and facing in the right direction given the fixed and free ends involved. Whenever possible, the beams were tandem lifted into position using 200 tonne and 160 tonne crawler cranes provided by Weldex. Where tandem lifting was not possible, a 500 tonne mobile crane was used to position the beams. This operation was logistically very complex and required considerable effort and skill from the supplier to ensure that all worked well, which it did.
Whilst the beams were being delivered and positioned, three concrete box structures were being built to accommodate the locations where one track was to pass under another. The Reading west box, where the existing freight line passes under the viaduct travelling toward Didcot, had to be constructed when possessions were made available because the freight line was still in use during construction.
The second box is located at the other end of the viaduct where the new freight line passes under the viaduct toward the station and the third box transfers the Cross Country route off the Festival Line viaduct which runs alongside and then underneath the main viaduct. These three box locations are significant structures in their own right with 900mm diameter piles running longitudinally, supporting the box walls.
An insitu concrete deck was then constructed over the precast concrete deck beams and finally insitu cantilevered walkways constructed over the deck edge beams ready to receive the ballast and track.
Clement was keen to point out that, wherever possible, material excavated from site was being recycled and the demolished material from the old train depot and ancillary buildings was being crushed and regraded. The material was then being used to provide fill for the reinforced earth ramps at either end of the viaduct.
The area close to the demolished depot and the new freight line was a wetland area and, to compensate for the loss of this land, Network Rail agreed with the Environmental Agency that they would construct a reception pond with flood relief culverts constructed underneath the new freight line.
Network Rail estimates that, by using combinations of imported fills from 100% recycled sources as well as the reuse of pile- arising materials from the works, they will achieve over 90% diversion from landfill. This is, without doubt, a significant achievement.
Throughout the project there has been a determined effort to complete the work ahead of schedule. Already, the Reading project team has shaved off a total of twelve months off the original timetable which, as Clement pointed out, is mainly down to time saved revamping the civils work. As part of this on-going effort, Clement explained that there is a concrete laboratory on the viaduct site and a technique called ‘Match Curing’ is used to determine the strength of concrete.
Normally, sample cubes taken from a batch of concrete are crushed to determine its strength. However, the concrete cube does not necessarily reflect the true strength of the insitu concrete which has the capacity to generate considerable heat and therefore additional strength. So, using the ‘Match Curing’ technique, electrodes are inserted into the insitu concrete to measure the temperature and the sample cubes are kept in a bath of water maintained at the same temperature. As a consequence, it has been possible to determine accurately the higher strength of the insitu concrete compared to the cube and therefore commence the next phase of work in advance of the programme. This simple initiative has enabled the team to make some significant savings in time.
All deadlines met
Clement was keen to reveal that the team has not missed a deadline yet on this project. He believes that, by working alongside the many different groups of skilled people involved in this project, including Balfour Beatty staff, reinforcement fixers, carpenters and scaffolders from SWORD, URS environmental advisors and crane operators from Weldex, they will continue to deliver on time. At any one time there are more than 400 personnel on site and they all appear to share Clement’s determination to meet the deadlines.
The viaduct will be completed by the end of July this year ready for track installation by Network Rail. The Festival Line viaduct and Freight Line will be completed by mid January 2015.
So, it looks like the final piece of the Reading project jigsaw will be in place well ahead of time. This is great news and there will be a worthy railway asset in place for generations to come. The layout will also be equipped with the necessary infrastructure required for the next phase of development, the electrification of the GWML.
As a footnote, once the tracks are in use over the viaduct, Network Rail will be able to complete the widening of Cow Lane from one lane to two. It will also be lowered by about two metres which will then allow buses to use this route for the first time. Cow Lane is a notorious bottleneck, so motorists as well as rail passengers will be able to appreciate the full benefit of this fascinating project.