On any rail project that affects the track, it is the replacement of the permanent way that attracts most attention. Ironic perhaps as it is usually this part of the scheme that is started last.
It will be a familiar tale. Only once everybody else has finished their tasks does the p-way contractor get his turn, with whatever time is left in the programme, and with the end of the possession relentlessly drawing near.
The p-way contractors are, therefore, often the unsung heroes of many projects. Their work can effect the perceived success, or otherwise, of the entire scheme, and there is often little recognition of the challenges that they have had to overcome along the way.
Typical of these challenges are some of the issues that Story Rail have encountered on a selection of their projects in the last year.
Working with Network Rail on the viaduct at Huttons Ambo, near York, Story Rail’s challenge was how to replace 46 longitudinal timbers on a structure where the supporting steelwork arrangement was subtly different on almost every span along its 100m length.
Accurate engineering was the key to making this project a success. The structure was surveyed using a total station and every replacement longitudinal timber was custom cut to suit the specific site dimensions. This meant that elaborate notching and drilling was found on every piece of timber, with all faces other than the top often needing several pieces carefully removed at the timber mill.
Lifting out existing longitudinal timbers is always a venture into the unknown. Any packing and holding down arrangements are often hidden to some extent, so lifting off the first timber usually gives a good indication of how well the possession will go.
At Huttons Ambo an advance possession trial lift was carried out on one of the timbers and this proved invaluable in helping to plan methodologies and sequence the works.
Thanks to this careful planning the replacement of the Up line has been successfully completed and the work to the Down line is scheduled for a forthcoming possession.
Story Rail carried out phase 6 of the progressive renewal of the slab track within the Merseyloop underground system in central Liverpool for Birse Rail.
The existing layout uses concrete sleepers cast into a concrete haunch running along the tunnel lining. Over time the sleepers’ housings have decayed and this has increasingly resulted in loss of track gauge.
The solution was to completely remove the existing track before forming a new in-situ reinforced concrete slab track with the rails mounted on Pandrol Vipa baseplates.
To construct the new track the existing rails were first removed and the concrete and sleepers broken free of the tunnel lining using an excavator mounted breaker.
The spoil was loaded into rail trailers and hauled away for disposal. Joiners and steelfixers then installed the shuttering and reinforcement needed for the new slab.
Lastly, ready-mix concrete was hauled into the site in an RRV trailer-mounted mixer and pumped into the formwork. Once sufficiently cured, the new track was constructed on top.
Following the successful delivery of phase 5 a year earlier, this was a chance for Story Rail to build on the skills that were already learned but at the same time to enhance the methodologies used.
One of the major difficulties that were overcome on the previous phase was the development of a method to move 100m long lengths of new rail into the tightly curved tunnel, and to then hold those rails precisely in their correct alignment while baseplates are fixed in place and grouted.
The solution that Story Rail developed was a custom-designed set of rollers and jigs that carried the rails through the tunnel and then held them in precise position in a safe and controlled manner.
The system worked so well that for phase 6 a further development was introduced to also lift the third rails into place. Previously a more traditional method had been used, with an RRV moving the rails on rollers and a combination of men and machines completing the final positioning on the insulated pots.
This contrasted sharply with the elegant way that the running rails were handled, so in the intervening period between phases 5 and 6 Story Rail’s engineers and fabricator set about designing a better solution.
With the running rails in place before the third rail a series of jigs could be built that sat on top of the track.
Centrally mounted rollers on the jigs then carried the new rails through the tunnel. Once the rails were adjacent to their final position, the turn of a handle moved them sideways until they were directly above the pots. From here a series of in-built jacks carefully lowered the rails into place.
This impressive piece of kit performed exceptionally well and its contribution to the safe delivery of the scheme resulted in Story Rail winning a Highly Commended award for Innovation from Birse Rail in their annual Supply Chain Awards.
Story Rail installed the permanent way on Arnside Viaduct for May Gurney during their recent deck reconstruction project, as featured in the rail engineer issue 80 (June 2011).
The track was constructed from Pandrol Vipa baseplates mounted on steel stools that were part of the deck panels. The fast pace of the job meant that the p-way had to finish within 48 hours of the last deck panel being placed.
Debate centred on what would be the best strategy. Would it be best to hit the site hard with resources once the decks were complete and do the lot in a couple of days, or keep a small gang working steadily just a few decks behind the rate of progress?
The advantage of the latter was that the task would remain a steady controlled process with plenty of opportunity to refine resources and techniques.
The disadvantage was that setting out the Vipas was more difficult when working from just one end – if installing onto the finished deck then the engineer would need little more than a string line to keep the alignment straight.
Steady and controlled won the day and the engineering issues that this created were overcome by good planning and the use of a total station to individually set out each baseplate.
The decks were installed to very accurate tolerances, with the final slight adjustment to the baseplates made using packing plates.
The bridge is over 500m long, and with baseplates at 600mm centres, over 3,000 baseplates were needed in total for the two tracks. Each one had to be placed by hand onto the stools so there was a lot of manual lifting.
This process was carefully monitored and Story Rail also designed and fabricated lifting tools that fitted into the fast clip housings of the Vipas, providing a sturdy handle so that two men could safely lift each baseplate into place without any bending.
Once all of the decks were fitted with baseplates the new rails were installed. Inspired by the success at Merseyloop, and the need to protect the paint finish, custom built assemblies were used that spanned between the stools. These supported the rails clear of the deck while they were moved onto the structure by RRV ready for final positioning into the baseplates.
These examples give just a flavour of the many challenges faced at the end of a major project when it is down to the p-way team to finish off the job.
Every scheme is different and each brings its own particular engineering problems that must be overcome to keep the contract on schedule. Story Rail has met and overcome those challenges over recent years, and will continue to do so in the future.