Why does a cliff just to the west of Dover have the name “Shakespeare”? Apparently, the famous playwright was actually at Dover, in 1597, to perform some of his plays with his travelling players – the “Lord Chamberlain’s Men”. Being struck by the drama of the local cliffs and their setting, he included the locality in a later play, King Lear, specifically Act IV Scene VI where the characters conversing on the cliff top are suitably awestruck by the scale of the landscape. Looking down, Edgar is moved to say:
“How fearful and dizzy ‘tis, to cast one’s eyes so low!……..
“The fishermen, that walk upon the beach, appear like mice……almost too small for sight.
“The murmuring surge, that on the unnumber’d idle pebbles chafes, cannot be heard so high……”
Anyone that stood in the same place between January and August this year would have observed, not fishermen, but, on almost any occasion, the staff and subcontractors of Costain earnestly toiling night and day to reconstruct and replace a severed link in the south eastern rail network. And, instead of pebbles, eight-tonne rock armour.
Two and a half centuries after Shakespeare’s Dover visit, the rail network was beginning to take shape. To create the link along the coast between Dover and Folkestone, the railway hugs the chalk cliffs all the way, disappearing where necessary into three tunnels, Shakespeare, Abbotscliffe and Martello.
Where possible, the line is carried on shelves cut into the chalk face. Heading west from the area of Dover town and harbour, the available space for the route narrows until, for the last few hundred metres as it approaches Shakespeare Cliff and Tunnel, the alignment was taken across the beach itself at the very foot of the cliffs.
In 1849, a long timber trestle viaduct was constructed to carry the railway across this area. The unusual arrangement caught the eye of local artists and the scene, complete with passing train, made for an attractive image.
Perhaps conscious of accumulated attrition to the wall on the seaward side of the viaduct in 1927. At the same time, the entire space behind this new wall was backfilled with chalk spoil, a ready supply of which was available from tunnel works being carried out in Dover at the time. This infill effectively buried the timber viaduct right up to the soffit of the track structure.
And so it remained, apparently serviceable, until Christmas Eve 2015.
Closure and reopening
During routine track inspection on that day, the alarm was raised and the line was closed after the discovery of sinkholes in the track formation. Storm damage had finally found out weaknesses in the sea wall and the chalk infill had been leached out, leaving several voids. These had already caused the track to be undermined, with top and alignment severely compromised. Also, some of the footings of the public footbridge to Shakespeare beach were no longer supported.
Not only were the obvious authorities, Network Rail and Southeastern, involved in a recovery plan but, unusually, the local Member of Parliament, Charlie Elphicke, also took on a key role early in the proceedings. Representing the people of Dover and Deal, he was keenly aware of the criticality of the rail link and that the severity of the damage was likely to lead to a prolonged period of disruption.
Rail Engineer was invited to the re-opening of the route on 5 September. It was very clear from the speeches made that the successful completion of the remedial works, well in advance of the forecast date and under budget, was in no small way due to the concerted and effective partnership between all the participants. Kent County Council, Dover Town Council and Dover Port authority were also praised for their co-operation in facilitating the works and the interim local transport planning.
Train services through Dover are complex, with trains linking to London Victoria, Charing Cross and Cannon Street and the high-speed services to London St. Pancras. The loss of one part of these services’ normal routes, following the closure of the line at Christmas, meant that a new train plan had to be devised. This was produced, including a bus link between Folkestone and Dover, in time for resumption of business demand straight after the New Year.
David Statham, managing director, Southeastern, paid tribute to those responsible for achieving in three days what would normally have taken 12 weeks to produce and check. He also thanked all local station staff in the implementation and sustaining of the new service plan.
Alan Ross, Network Rail director route asset management, extolled the excellent working arrangements between the company, the main contractor for the works, Costain, and Southeastern. He also praised the support and political help received from Charlie Elphicke and two other local MPs. Charlie Elphicke himself congratulated all parties involved and emphasised the success of Costain’s work.
Back, now, to the beginning of these successful collaborations in December 2015/January 2016. A task force had been quickly formed between all the parties mentioned above, with Costain appointed as main contractor with a design and build remit.
Consultant Tony Gee and Partners proposed five main options for recovery. These ranged from armoured earthworks through to a full new track support structure. Even reinstating only a single bi-directional line was considered, in the interests of an overall shorter project timescale.
At one stage it looked as though the line would need to remain closed for up to two years. However, a challenge from Charlie Elphicke to come up with a solution that could achieve line re-opening within a year was made and the role of this local MP remained important in sustaining the momentum of the project.
Three high profile visits during the works, including one from the Secretary of State for Transport and one from the chief executive of Network Rail, Mark Carne, re- emphasised the economic importance of re-establishing this railway link as quickly as possible.
The solution selected by Network Rail, and also Costain’s preferred option, was to construct a reinforced concrete raft, supported by bored piling and carrying a two-track railway as previously. This new viaduct would be 235 metres in length.
Meanwhile, as these feasibility studies and discussions were continuing apace, it was imperative to prevent further damage to the sea wall and loss of material from the track support zone. Commencing as soon as possible after the New Year, sheet piling was installed along and in front of the affected parts of the wall, using tidal working from the beach in approximately four-hour periods. Rock armour was then placed between the piles and the sea wall.
Design of the new reinforced concrete viaduct progressed in conjunction with site investigation. After removal of the existing track and exposure of the old timber work (see picture), it was apparent that, rather than attempt any significant clearance of the old timber and chalk, it would be most efficient to core through all this material and install piles into the bedrock beneath.
The final design used 134 bored, cast in-situ, reinforced concrete 900mm diameter piles. These were typically 30 metres in length, being roughly 10 metres through made ground and 20 metres into bedrock. Charly Clark, project director for Costain, said that a crucial part of the piling operation was to prepare the remains of the old track support area to become an adequate working platform from which the very heavy piling rigs would be progressively working.
The superstructure of the new viaduct is a 600mm deep reinforced concrete raft, which was cast in four pours. The volume of concrete required for the raft alone was 1,933 cubic metres. The pours were planned to be carried out at weekends, primarily to reduce the risk of delays in concrete delivery to site that might have been experienced in weekday traffic.
Two concrete batching plants were used, one very close to the site, with a back-up at Ramsgate. Integral with the raft is a reinforced concrete upstand wall on the seaward side of the track. This serves as a sea spray protection barrier.
Charly confirmed that all four major concrete pours went according to plan, with no significant issues. It was obvious that Costain was pleased and proud to get this major part of the project successfully installed. Throughout the whole project, Costain had between 65 and 70 staff on site at any time, working in two 12-hour shifts, night and day. At peak times, there were up to 170 staff on site.
Now that the immediate priority of reopening the route has been achieved, there remains much associated work to be done before the site will be demobilised in May 2017. Firstly, the public footbridge to the beach is being reconstructed, this time using fibre-reinforced plastic as the structural material. Most importantly, 130,000 tonnes of rock armour has to be placed alongside the area of the new viaduct. Steve Kilby, senior programme manager for Network Rail, told Rail Engineer that this material, which is imported from Norway, is transhipped from large delivery boats at Dover harbour and brought round to Shakespeare beach in 5,000 tonne barge loads.
The rock armouring is graded in three sizes, 1.5 to 3, 3 to 6 and 5 to 8 tonnes. This material is graded into the protection, which also includes a geotextile. The lower part of the old sea wall is being kept to retain the rock armouring.
The redundant upper part of the wall is being demolished.
All this work could not go on concurrently with the viaduct construction as it was necessary to obtain a licence from the recently established Marine Management Organisation. Although the MMO had granted a licence for the emergency works, carried out initially from the beach, fuller procedures were needed for the approval of the permanent works so this could not commence until the beginning of August.
In the period that the whole route between Folkestone and Dover was closed for the main remedial works, Network Rail took the opportunity to carry out a great deal of maintenance and renewal work. Because the normal operation of the railway was suspended between Dover and Shakespeare tunnel, within that area it was possible to use engineering trains and other resources with simpler rules and regulations than for normal possessions, whilst still ensuring completely safe worksites.
2.5km of track was renewed, this being done on Tuesdays, Wednesdays and Thursdays to avoid impacting resources already committed for weekend renewals. Other work that was carried out included drainage and repointing in tunnels and general vegetation management. The opportunity was even taken to mount a full emergency evacuation practice from a Javelin train in Shakespeare Tunnel.
In Charly Clark’s opinion, the outstanding feature of this project was the very close co- operation between client and contractor. He found that this was especially beneficial during the optioneering process, when alternative remedies were being evaluated. The situation quickly evolved from disaster prevention to an agreed way forward. Borehole information was gathered and consultants appointed and the direction of the project, and the budget, quickly agreed by the client. Once that had happened, the agreed programme remained unchanged throughout.
Although a target reopening of one year was announced publicly, this included a contingency of three months. In the event, none of this contingency was required and the anticipated final cost is estimated at £39.8 million against the budget of £44.5 million.
“All’s Well That Ends Well” as the great playwright asserted.
Written by Mark Phillips