feature
commissioned to flowing beneath the wall footings into the arch support stones later. In any event,
carry out a full site formation. In addition, the wall was the arches had stood for a century and a
investigation. This anchored back throughout its 375 yard half, keyed in at the base with the rest
included length. just mortared against the existing face of
topographical the wall.
surveys, track Trial run The first arch to be removed took about
surveys, ground In advance of the blockade two 29hr 10 hours, but by the time the 16th arch
investigations and possessions were made available by the was taken down this time was reduced to
probing the train operating companies to enable a about 3 hours. The cutting operation took
construction of the productivity assessment of piling and between 45 minutes and an hour. During
retaining walls anchoring subcontractors and to discover the first cut, the wire became trapped as
themselves. The footings for the wall any snags with the installation of the the stones eased away from the wall.
were found to be between 0.75m and anchors or the piles. 'This was the trial Some judicious use of steel wedges
1.5m deep – fairly deep by the standards run,' says Stephen. 'The information was remedied that issue on all the other
of the day, but not in relation to the track vital to building a secure programme for arches.
and drainage excavations needed to the main closure.' The successful piling
secure the route. contractor was Steel Piles Installation. New drainage
Whilst Permanent way engineers had At the start of the closure, main sub With the arches out of the way and the
relayed the track beneath the arches contractor Stobart Rail brought in stone to steel props in place, work could start on
many times without hitting the arches, it blind over the tracks to give a level securing the retaining walls. This, and the
was felt that tampering with the retaining working surface. As each arch was drainage work, was carried out by Stobart
walls would be just too much of a safety removed, a new temporary steel prop Rail. The new 450mm diameter six foot
risk with the arches in place. Only a very was installed. Severing the arch from the drain has been installed through, at times,
minor movement of the walls – either retaining wall was achieved by wire difficult soil conditions. This, along with
inwards or outwards could bring the cutting down close to the wall face. new cess drains, has sorted out the water
arches down. This didn't need detailed Holemasters, experts in this technique, problems. The trench sheet piles have
analysis – just looking at them it is used a cutting wire encrusted with been burnt off at cess level and remain as
blindingly obvious! industrial diamonds. The arch was a water cut-off.
supported in a steel cradle – again, each The arches were – and still are – Grade
New steel arches one different. This was offered up to the II listed structures. Network Rail had to
There were sixteen flying arches. They underside of each arch by a pair of large obtain listed building consent for the
were all different and spaced at uneven fork lift machines working in tandem. As works, and part of the consent requires
intervals along the site. Nobody knew each arch was freed, they lifted the cradle that the removal is only temporary. The
what forces the arches were resisting – if clear of the wall and lowered it to the arches have been removed intact,
they were resisting anything at all. The ground. The cradle was then taken away carefully numbered and taken to a secure
cautious approach prevailed and by road rail machines to the access points. store. They are to be reinstated within
temporary replacement steel arches were three years and there is a team of
designed to take the full force of the Design or afterthought? architects on standby to work out how
retaining wall. In the end, these have The clue to whether or not the arches this is to be done.
proven to be fairly elegant galvanised were built as an afterthought comes from This in itself will be a tricky job. They
steel structures. These too were all the way that they were supported on the can't go in exactly as they were because
different. wall. There was only one stone on each of the headroom problems and the need
Work was also specified to secure the side keyed into the wall at the base of an to accommodate future electrification
retaining walls and also to ease the water arch. The arches were not set out at options. In any event, the track is now
problems in the formation. Trench sheets regular intervals and the retaining wall much higher. Now that the £5M project is
were to be driven down the face of each stonework bedded to suit. Rather it looks complete, the old swoop under the arches
wall. These were primarily to act as water like the wall was built and then stones has gone and the track has been replaced
cut-offs to intercept the water that was were plucked out to accommodate the by Babcock Rail to 95mph standard.
42 | the rail engineer | october 2008
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