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R.o.B Railways to Europe
The Channel Tunnel
Including:
The Channel Tunnel Rail Links Phase 1 and 2
(Now referred to as High Speed 1)
Design: To develop, finance, construct, and operate the channel tunnel system a private Company was given a 55 year concession which was later extended to 65 years. Eurotunnel was formed of two separate companies, one based in France, Eurotunnel SA, the other in Britain, Eurotunnel Plc. To build the tunnel they had to raise the capital through various different means. The construction work was sub contracted out to a consortium of 10 companies. Euro tunnel has total control of the operation including the tunnels and termini. This involves signalling, power supply, ventilation and drainage as well as technical safety and security. Many different designs and practices were studied at design stage of the tunnel researching the possible experiences, good and bad that the tunnel may face at any one time. This was no mean feat as the whole project was being pieced together from scratch and was something that had never been accomplished before though many projects had started then failed. Despite this it was realised that proven practices and designs had to take precedence over the other newer ideas in an attempt to heighten safety and efficiency as well as keeping costs and failures to a minimum. Before construction commenced surveys were carried out using, what was then, state of the art technology, normally used for deep sea oil drilling. This told engineers exactly what was beneath the sea bed and how stable the bed rock was. It was found that the sea bed itself was formed of deep valleys and furrows that were filled with sand and mud, but beneath this there were layers of chalk and other solid rock. This was ideal for the construction of the tunnel which was bored through the chalk.
The Tunnels: There are three tunnels, two for the standard gauge rail traffic and one central one that acts as a service tunnel and ventilation system all of which are 50km long. The tunnels were built through mostly chalk marl at an average depth of 45m below the sea bed with the deepest point 75m below the sea bed. The tunnels are reinforced with concrete or cast iron linings, the two running tunnels are of 7.6m diameter and are parallel at about 30m apart with the 4.8m diameter service tunnel between the two. Every 375m there are cross passages that provide ventilation and if necessary emergency exits. For travel through the service tunnel special vehicles were designed that had two driving ends. The original idea was for a narrow gauge railways system but it was decided that this would not provide enough flexibility. The service tunnel transport system vehicles as there official title is are controlled by a wire guidance system similar to the prototype bus routes operated by First group in York and East London. At 4 points on the system there are crossover halls that allow trains to change to the opposite tunnel should it be necessary when there is maintenance work under way or if there is an emergency. When not in use huge steel doors separate the tunnels to reduce wind flow from the other tunnel. To allow the crossovers the service tunnel drops below the running tunnels and comes up to one side. There are two tunnels under the sea bed with the other two crossovers close to the tunnel exits on land.
Construction: Most of the boring for the tunnels was done through chalk marl. 11 tunnel boring machines (TBM's) dug out the spoil and lined the tunnels with the pre-cast reinforced concrete liners. When approaching the site of the crossovers the concrete was replaced by cast iron as this made it easier for the relevant connections to the hall lining. At the starting points on land 2 TBM's would be lowered down to start boring back to back at the bottom of a huge excavation. One proceeding out to sea the other proceeding in land. The British starting point was at Shakespeare cliff near Dover with the French site at Sangate near Calais. Each of the three main tunnels had a TBM operating from each end but the rail tunnels in land had only one machine each which upon reaching its destination was turned back and sent back to create the next tunnel. The British site was built so close to the original tunnel attempt of 1974 it was able to utilise some of the remaining works to give access to the upper and lower bore sites. In the two adits that were created in 1974 a ventilation system was fitted in one while the other operated a narrow gauge railway that utilised a rack and pinion arrangement to get up the steep incline. This little line was used to transport materials, equipment, spoil and personnel in to and out of the main tunnels. As the TBM's dug, the spoil was emptied in to railway wagons at their rear and the trains were then hauled to the foot of the main vertical shaft where the spoil was tipped and mixed with water to allow it to be pumped to the surface as slurry. On the British side the service tunnel was completed first, with the 3 tunnels eventually meeting in different places between 17 & 22km from the starting point at Shakespeare cliff. The TBM's would stop tunnelling 2km from the terminal at a place called sugar loaf hill with the rest of the route been constructed by the cut and cover method.
Track work: When tunnelling was completed in June 1991 each of the three tunnels had a 900mm gauge construction railway running through it. This aided in the finishing touches to the tunnel construction which involved the building of the cross passages, crossover chambers and the plant rooms. Once these were completed work started on the building of the standard gauge running lines. Overhead catenary was installed once the track was in place and the electronics and cables for the signalling were also installed. The tunnels are of standard gauge single track formation which is used in the majority of Europe. However one problem was the loading gauge which is wider on the continent than it is in Britain. This means that European trains cannot run over most British railways past the Folkestone terminal. During the BR metrification the width of the rail gauge was reduced by up to 3mm from 1.435 to 1.432m to improve the riding of trains at high speeds, there are 25.4mm or 1 inch.
The rail in the tunnel is 60kg/m flat bottom rail which is commonly used in Europe especially on French high speed routes is held in place with sprung bolts holding the rail to the sleeper blocks. Due to the relative constant temperature of the tunnel the rails do not have expansion joints and are continuously welded for their entire length except at the emergency crossovers. In the open the rails are provided with expansion joints to reduce the effect of buckling. The track supports were designed to have a life span of 50 years due to the lack of maintenance time available. The sonneville system is used to support the rails which comprises of pairs of reinforced concrete blocks to support the rails at 600mm intervals. For resilience the rails sit on 'H' shaped pads of microcellular ethyl-vinyl-acetate (EVA) with a grooved surface. Screw fastenings attach the pads to the blocks. Nylon clips and EVA pads provide electrical insulation to ensure the proper operation of the track circuits in the tunnel conditions which are damp and salty. A rubber boot surrounds the bottom of the sleeper block providing further insulation. In the undersea crossovers the point work is laid on longitudinal wooden sleepers with the track and point work encased in rubber seals as a protection against derailment and to help seal the closed doors. As with all modern track the rails are laid on a slight inward cant thus reducing the amount of wheel on the rail at any one time. This reduces friction whilst allowing traction therefore reducing energy expenditure for train movement and drag caused by friction also in the long term reducing rail and tyre wear. The Sonneville system also allows low aerodynamic resistance by the air displaced from the front of the train passing along the sides and under the train filling the vacuum that the speed of the train in the tunnel causes. The air however becomes superheated and is cooled by pipes full of flowing cold water.
Operation: The tunnels are not lit but there is emergency lighting when necessary. To drive the air in to the tunnels huge fans on land at either end of the tunnel draw air down a vertical shaft in to the service tunnel which is maintained at a higher pressure to the running tunnels. When the trains pass through either tunnel they draw the air with them from ventilation shafts that are situated every 250m. The tunnel had been designed and built for the carriage of passenger and freight trains between Britain and the continental Europe. The tunnel opened to ferry style traffic, where cars and Lorries could drive on to purpose built trains in, 1994. This service is called 'Le Shuttle' and operates between purpose built termini at Calais and Folkestone. Overall operating responsibility for the railway, tunnels and all support systems comes down to the control centre at Folkestone terminal. There is also a back up control centre on the French side that would take over in the event of the Folkestone site not operating correctly. If any event occurs that does not affect the overall operating and control of the Folkestone control centre then automatic fail safes cut in, such as if the signalling fails the computers automatically stop all trains. Though there are obviously people overseeing everything the system normally works on automatic. All traffic except shunting away from the main lines is done to a carefully planned timetable though there are more than enough train paths for slight adjustments.
Traffic: The Channel tunnel allows rail freight users to load their goods on to trains at any point in the UK and transport it rapidly and cheaply to mainland Europe with the minimum of hassle. The system as has been mentioned previously has been built to cater for ferry type traffic which a large proportion of are lorries. It also caters for through rail freight from Britain and the continent as well as passenger services from London Waterloo. Prior to the opening of the Channel tunnel BR rail freight moved about 2,000,000 tonnes of freight a year to and from the UK channel and north sea ports. To cater for freight traffic through the tunnel new wagons and flat bed inter-modal carrying trucks had to be purpose built for use over BR now Network rail lines due to the aforementioned loading gauge difference. To cater for freight services a new class of electric locomotive was built for BR classified class 92. Not only does the tunnel channel, excuse the pun, freight services through to Europe but also provides for the High speed 'Eurostar' services which run from London Waterloo to Paris/Lille/Brussels. Today the CTRL phase 1 takes these services from the South Eastern railway, Kent lines at Fawkham junction through to the Folkestone terminal and on through the tunnel at speeds up to 183mph. The CTRL phase 2 is under way for the extension of the CTRL 1 to London St Pancras which will see Eurostar trains arriving in the classical train shed allowing easy interchange for trains to the north from St Pancras, Euston and Kings Cross.
Before the CTRL: As was mentioned above a high speed rail link was also among the proposals when the studies were put forward for consideration. On the French side the infrastructure was already in place and was built for the TGV services. However the British side only had the ex London Chatham and Dover/London and south eastern lines between London and Folkestone which carried normal commuter traffic and still does! Obviously this was not going to be suitable as 'Eurostars' had to trundle along at 50mph between London Waterloo and the tunnel and it is an obvious slow down from the speed in the tunnel (I know I went on it when it first opened! It was Brilliant!!!). Something needed to be done. Phase 1 of the CTRL was opened in October 2003 after 5 years of construction. It runs from the channel tunnel to Fawkham junction in Kent. It also made British railway history by being the first new railway of the 21st Century and also the first main line since the Great Central built their line from London Marylebourne to Carlisle. The CTRL runs predominantly alongside existing roads and railways to minimise the environmental impact. The line even runs over some previously closed railway.
Fawkham Junction to North Downs Tunnel: Fawkham Junction is situated on the Swanley to Rochester line and forms the present connection for trains to Waterloo. North of this junction the trains share Network rail lines with commuter traffic. From this point the line follows in a North easterly direction the former track bed of the Gravesend Railway to Gravesend west. The Gravesend railway came about as competition in the 1880s between the London, Chatham and Dover railway and the South eastern railway. This former line opened in 1886 after becoming part of the LC&DR. The line never developed in to what had been planned as a heavy trunk route and was closed for passenger services by BR in 1954. It did however remain in use for freight serving Gravesend west Goods yard and some local industries. In 1959 the route was singled, though in the 1960s more cuts took place with the line been shortened with the Southfleet to Gravesend West section being closed in 1968, Southfleet serving a cement works and the rest following suit in 1976. Bridges have been rebuilt to withstand the weight and speed of the new trains on this section of line. Just short of where Southfleet station used to be the line curves to the south east to run parallel with the A2. There is a flying junction here that goes over the top of the CTRL phase 2 that will extend to East London and London St Pancras International station. Coming of the fly over the CTRL high speed line actually starts and trains accelerate at a good pace to a line speed of 186mph. At Singlewell next to the A2 still, passing loops have been built. Past here the line dips in to a tunnel beneath a roundabout and then goes down in to the Medway valley. The line dips in to a single bore double track tunnel to emerge on the south side of Bluebell hill.
North Downs Tunnel to Ashford international: The line runs through several tunnels along this stretch some of which are to ensure the scenery is not spoilt. I wonder what the original railway engineers would have thought of that! The line then follows alongside the M20 before crossing the Maidstone to Ashford line. Again here is a set of passing loops called Charing Crossover(Witty!) but there is a place called Charing nearby. Some of the tunnels on the next part of the line were constructed cut and cover style much like the practice used on the early London underground lines. After the line has crossed over the M20 it passes the former construction site at Beechbrook farm. This site was squeezed between the Maidstone to Ashford line running north to south and the CTRL and the A20. The terminal had connections with the Ashford line and opened in 2001 was built on farmland on the condition that when the line was complete it would be returned to farmland. It has been and no trace of the site now exists. In most of 2002 it was home to a wide variety of locomotives and rolling stock that was been used in the construction work. At one time it contained class 08 shunters, class 20s, class 66s and even a class 14 long since gone from Br records!! All the major freight haulage companies used the site and it must have been a joy to railway enthusiast to see such a variety of locomotives and stock. After passing under the A20 the line climbs a steep gradient towards Ashford before passing through another cut and cover tunnel. At the end of this tunnel there are connections to Ashford international station while the CTRL passes through a cutting and then over a huge concrete viaduct on the north side of the station crossing the Canterbury line.
Ashford International to Folkestone: The lines from Ashford rejoin the CTRL just after Ashford at the eastern end of the viaduct. The CTRL then runs alongside the Ashford to Folkestone line. The line passes through several small tunnels and passes close by Westernhanger station and Sandling stations. At Dollands Moor west junction the CTRL splits in to 2 separate single track sections and there is also a connection to Dollands moor yard where freight from Europe is brought to. The CTRL then joins the existing eurotunnel route at Cheriton terminal and then off through the tunnel and in to main land Europe. The up London line crosses Saltwood tunnel and then drops down the south side of the Folkestone line running mostly on viaduct to join the existing line at the site of the former Continental junction.