Examining The Channel Tunnel Engineering Projects Construction

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The Channel Tunnel (Gallic: le tunnel sous la Manche), widely recognized as one of the universe’s greatest civil technology undertakings, is a 50.5km underwater rail tunnel linking Folkestone, Kent in the UK with Coquelles, Pas-de-Calais in France under the English Channel. Even though it began building in 1988 and was opened in 1994, the thought to hold a cross-channel tunnel was foremost mooted more than 200 old ages ago but did non happen due to political, national security, and cost considerations. However, with the enormous addition in traffic growing, better and alternate agencies of communicating, convenience, and velocity were necessary and therefore the demand for an alternate conveyance path was apparent. The demand for such a tunnel was further compounded with Britain’s fall in the European Community and the cross-channel traffic duplicating in the last 20 old ages (taking to the undertaking), reflecting improved trading between the Britain and remainder of Europe. The Channel Tunnel would besides be able to supply an alternate competitive nexus between the transit systems of the UK and France, supplying both velocity and dependability to freight bringings. With the strong endorsement from the authorities of both crowned heads, the determination to construct the Channel Tunnel was therefore made. In April 1985, the British and Gallic authorities issued a formal invitation to possible tenderers for the fixed Channel nexus, and finally, the contract was awarded to the pool Channel Tunnel Group Limited- France Manche S.A. (CTG/F) (subsequently renamed Eurotunnel).

The Channel Tunnel, with the authorities’ purpose that it be in privately funded and at that place would non be any authorities aid or project, was a build-own-operate-transfer (B-O-O-T) undertaking with a grant. In this contract agreement, Eurotunnel would be the proprietor semen operator, which was being funded by the Banks and stockholders. The authorities of the UK and France were represented by the Inter-Governmental Commission (IGC), to which the Safety Authority and the Maitre d’Oeuvre (an independent proficient hearer) would describe to. The IGC would so do concluding technology and safety determinations. TML (basically split from CTG/FM to divide the functions of owner/operator and contractor) consisted chiefly of five British contractors (Translink Joint Venture) and five Gallic contractors (G.I.E Transmanche Construction) and would transport out the building works for the Channel Tunnel in a design and construct contract. Upon completion of the undertaking, the British and Gallic authorities would present Eurotunnel a 55 (which was later revised to 65) twelve-month running grant to refund the Banks and stockholders. The contract was officially signed on 13 August 1986 and the fixed rail was to be to the full commission in 1993. The services offered by the Channel Tunnel include the Eurotunnel Shuttle (a bird service for vehicles), Eurostar rider trains, and cargo bringing trains.

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TML ‘s contract was to plan, construct, and trial, and committee the fixed rail tunnel. The Channel Tunnel was designed to hold three concrete-lined dullards about 50 km long, with 37.9 km undersea and the remainder under land at either terminal of the English (Cheriton near Folkstone) and Gallic ( Pas-de-Calais small town of Frethun ) terminus. Two of the running tunnels were designed to hold an internal diameter of 7.6 m while the 3rd was a 4.8 m service tunnel running halfway between the two and connected to them via 3.3 m diameter cross transitions at 375 m intervals. 2 m diameter Piston alleviation canals linking the chief tunnels at 250 m spacing were built to forestall the accretion of differential air force per unit areas and aerodynamic opposition. To ease operations and care, four crossing-over caverns were built between the two terminuss to let trains to traverse between the running tunnels. Two crossing overs were laid near to the terminus while the other two were under the ocean floor, efficaciously spliting the tunnel into three about equal lengths.

Two separate rail tunnels were chosen alternatively of an individual big twin-track rail tunnel because this could minimize building hazards while at the same clip enhancing operations, care, and safety. The diameters were finalized after design analysis, development, and optimization services, taking into consideration the operation and support, velocity, and cost of building. The service tunnel provided an entree between the running tunnels during normal and exigency state of affairs and was equipped with a guided conveyance system. It was beside where the H2O and pumping brine run and functioned as a fresh air supply canal to the tunnels in normal on the job status. In add-on, the service tunnel would work as a lead tunnel during building which allowed the workers and applied scientists to measure and determine the chartless land conditions before progressing the chief tunnels.

Establishing on the bing geotechnical probes, past burrowing expeditions, and two extra geotechnical and geophysical studies carried out by TML on the English Channel along the proposed tunnel line, it was ascertained that there was a distinguishable sub-unit of the Lower Chalk bed known as the Chalk Marl running continuously between the two terminuss. Chalk Marl, made up of jumping sets of marly chalk and limestone, was found to be the best tunneling medium as it was impermeable (due to its high clay content) and provided good short-term stableness under digging, therefore minimizing the figure of supports required. It was designed to be bored in the bottom 15m of the Chalk Marl bed to minimize the immersion of H2O from the breaks and articulations, but above the Gault clay which is susceptible to swelling when moisture, enforcing high emphasis on the tunnel liner. The chalk marl strata dipped gently at less than 5° with smaller supplanting of less than 2m due to blaming towards the UK side; whereas the strata dipped badly towards the Gallic side (up to 20°) with much larger supplanting of up to 15m. Chalk at the Gallic side was besides harder, more brickle and fractured. This, therefore, led to the usage of different burrowing methods on the English and French sides.

The seaward and landward dullards for all three tunnels on the UK side began at Shakespeare Cliff. Construction traffic would come in the tunnel via a new inclined entree (Adit A2) at the Lower Shakespeare site, while worker entree was built via a shaft driven to the tunneling degree from the Upper Shakespeare site. Due to the fast building clip required and the comparatively dry chalk marl at the UK side, it was assessed that the New Austrian Tunneling Method (NATM) was most suited for the UK tunnels. One characteristic of the NATM was the interlinking of design, building method, sequence, and works and the success of this method depending on the uninterrupted integrating of these elements by the tunneling applied scientists. Six TBMs were used to drive the UK tunnels crossing an entire distance of 84 km. The TBMs were operated on an open-face manner with a forepart unearthing subdivision and a rear gripper unit which acted as an impermanent ground tackle point when the cutting caput drove frontward at 1.5 m increases. Excavation of the tunnel and hard-on of the tunnel liners were carried out at the same time. Depending on land conditions, the thickness of the liners ranged between 380mm and 500mm. An expanded concrete liner was used for the UK tunnels where the unbarred liner was expanded against the excavated land. Pads on the dorsum of the liner allowed the formation of a ring to be filled with grout to forestall H2O immersion. Every 1.5 m run a longing ring was made up of eight precast concrete sections with a cardinal section. Cast Fe liner sections were merely used in hapless land conditions.

Over at the other side, the tunnel thrusts started at the shaft in Sangatte in France. Due to the extremely fissured land ensuing in really wet conditions on the Gallic side, a different type of TBM known as the Earth Pressure Balance Machine was used. The TBMs were designed to run both in unfastened and closed manners. Close manner is characterized by the sealing off of the machine from the spoil around it and the cutting caput, therefore maintaining force per unit area on the soil in forepart as it excavated and letting the machine work in the prohibitionist as the force per unit area in the machine was higher than the outside. The agreement of seals on the TBM allowed it to defy up to 10 atmospheric forces per unit area. When the TBMs reached drier and more favorable evidence, they could so exchange to open manner. While precast subdivisions were besides used on the Gallic side, the stuff used was different owing to the different dirt conditions: neoprene and grout sealed bolted liners made of cast-iron and high strength concrete. The Gallic tunnels were made of six 1.4 to 1.6 m broad sections plus a cardinal section. A sum of 5 TBMs was employed on the Gallic side, and the dullards from the UK and France were to eventually run into the center of the English Channel in the tunnel breakthrough stage.

The Channel Tunnel undertaking was immense by any criterion, with a figure of cardinal factors that could potentially impact the parties involved: bi-nationality, private support (thereby efficaciously reassigning most of the fiscal hazards to the contractors), agenda, and cost. To remain attractive to investors and Banks likewise, the undertaking had to run into the undermentioned precedences: lower limit hazard of cost overproduction, lower limit operating cost, and upper limit traffic gross. It was recognized, from the beginning, that the chief challenge of the undertaking was to decide the logistical support associated with big graduated table tunneling and the fast-track nature of this undertaking. The direction, finance, and proficient challenges related to this undertaking would be explored in the subsequent paragraphs.

The first direction job encountered was the sourcing of the big figure of workforce required for the building of the Channel Tunnel. This was conducted against the background of the flourishing building industry where there was stiff competition for labor. As a consequence, TML scoured beyond France and UK for skilled labor including experienced applied scientists and tunnel mineworkers. TML besides set up a preparation strategy with Kent County Council and the Manpower Services Commission to fix workers for the myriad of occupations available as the undertaking progressed. The chief restraint for sourcing endowment was the high wage that accompanied them.

The 2nd direction challenge was to happen a solution to dispose of the immense measures of spoil that tiring 150 km of tunnels would bring forth. The job at Sangatte was solved rather easily as there was a suited land shit near the building site and spoil disposal was done by changing covering the tunnel spoil into a 50% slurry and so pumping it to the Ford Pignon dike above the site 3km off. However, there was a small infinite at Shakespeare Cliff and there was no suited land shit nearby. Even though backfill amounting to 3.6M three-dimensional meters of British spoil would be required at the ulterior phase of the building, there was still a staying 1.8 M three-dimensional meters of spoil that had to be disposed of. Eurotunnel finally found a solution which was to utilize the spoil to supply a level country of land at the pes of the Shakespeare Cliff which would be landscaped and used for recreational activities. When conservationists raised strong expostulations, Eurotunnel argued that immense logistical and traffic jobs would ensue if the spoil were to be transported elsewhere. In add-on, the spoil would be contained behind an expensive breakwater of sheet hemorrhoids and concrete designed to forestall the chalk mulcts from leaching into the sea. The constructed breakwater, crossing 1795 m long and up to 11.36 m midsts, was designed as a short-term groin and a long-term retaining construction. This land (made of spoil) was later transformed into the Samphire Hoe Country Park. Another facet of concern was the bringing of kinds of stuff to the site. Whenever operable, bringing was done largely by rail (for velocity and convenience) and the kinds of stuff delivered include the precast concrete liners, sheet hemorrhoids, and sums.

Following, another direction challenge was the method of obtaining the big volume of concrete required. 442,755 concrete sections of the highest quality mixed from strong, un-reactive kinds of stuff in 35 different sizes were required. They were designed to last 120 old ages subjected to burdens in the worst instance scenarios under two separate bound provinces and had to defy seismal activities, be watertight, and keep its structural unity regardless of the burden type. As it was evident that no precast company could provide such sections to carry through TML’s demands, TML had to make its ain precast pace at the Isle of Grain in Kent, bringing forthing sections of the strongest concrete.

In add-on, the determination to drive all the UK tunnels from an individual worksite gave rise to complex logistics jobs because it had to back up five TBMs at any one clip. They required 1000 precast concrete sections daily, together with other kinds of stuff such as paths, overseas telegrams, pipes, and vent canals. Besides, at least 18000 m3 of excavated spoil had to be removed daily. This challenge was solved by the procedure of separation: forces would come in the tunnel via the 110m deep shaft; spoil removed through Adit A1 on a 2400T/hr capacity conveyor and other kinds of stuff transported on the five-line railroad in Adit A2.

Furthermore, the three 50km-long tunnels had to be made an operational railroad through the installing of catenary systems, chilling pipes, drainage, paths among many others. Given the myriad of systems that had to be installed (e.g. 550 km of drainage, fire and chilling system pipes, 1330 km of overseas telegram fitted on the overseas telegram trays), TML had to pull off more than 40 subcontractors vying for infinite on the tunnel bringing trains. The right equipment had to be supplied to the exact location at the right clip; particularly when the bringing trains take more than an hr to negotiate the deep terminals of the tunnels and a missing point would hold caused hold to the plants. TML resolved this issue by running the tunnel works akin to a production line – a stuffs accountant was employed from the motor industry to guarantee smooth work procedures and led the coordination and planning attempts. Besides, TML constructed 4 diagonal cross tunnels linking the three chief tunnels to let the bringing trains exchange between the three during the services installing stage, thereby relieving the trouble of traveling the kinds of stuff and spoil to and fro the tunnel.

Sourcing funds for the mega undertaking was beside one of the direction challenges faced. Given that the initial appraisal of the undertaking cost is about 5 billion lbs, a big sum of money was required to see the undertaking through to completion. As the undertaking had to be privately funded, Eurotunnel had to begin beyond the national boundaries to procure investing. They, therefore, devised a funding strategy to assist them to surge the crisis: the strategy would supply for the cost of the tunnel to be financed by 5 billion worth of bank loans, with extra 1 billion equity from the proprietor, institutional investors and a public offering. Preliminary equity funding would be raised in two phases (known as Equity 1 and Equity 2). Equity 1 worth 47 million was raised by hard currency arrangement by the founding stockholders. Equity 2, deserving 206 million, came from both British and Gallic investing establishments. They subsequently came up with Equity 3, deserving 770 million, and raised it by the manner of public portion offering through the Paris and London stock exchanges at the same time. The Channel Tunnel undertaking was, therefore, able to continue.

Possibly one of the greatest direction challenges was how to enable the Gallic and British to work closely together. Separated by 34 km of sea, their civilizations are different. Furthermore, the edifice codifications and preparation (and therefore the bound provinces of design) were different. It was a challenge conveying two different technology manners together. To get the better of this challenge, it was decided that both states use their ain design codifications for their portion of the channel. Gordon Crighton, a Scot, was brought in to take the technology squad so that both the British and French would non hold dissensions since both states had good dealings with Scotland. This enabled the technology squad to work cohesively together. When it came to the design of parametric quantities, both the Gallic and the British had to compromise. For case, the English wanted the service bore to be 4.5 m in diameter, but the Gallic wanted 5 m. In the terminal, they agreed to a diameter of 4.8 m.

Besides the demand to get the better of the challenges faced in undertaking direction, a figure of proficient challenges besides had to be overcome. First, maintaining the machines in class was one of the most complicated proficient challenges faced. While most tunnel mineworkers use a hi-tech orbiter function system to chart the tunnel path, this system was non-effectual for the Channel Tunnel as it was excessively far submerged. The excellent and exact function was indispensable for if the British and Gallic tunnels were to be misaligned even by a little border, they would non be able to run into up every bit planned in the center of the English Channel. Therefore, the applied scientists developed a hi-tech optical maser counsel system. A ruddy optical maser on the cutting caput of the TBM would direct a beam frontward; hitting a control point which would relay the information to the computing machines onboard the service trains located behind the cutting caput to assist them to remain in class. This system enabled both squads of TBMs to successfully remain on the intended class and run into each other in the tunnel discovery.

Another proficient challenge was that the engines that were used to draw the tunnel liner sections and spoil trains broke down often under wet conditions. Under such conditions, the wheels of the engines lost grip and span on the inclines; and their electric systems were loaded with salt wet and frequently prima to malfunction and power failure. Even though the engines were designed to be powered by a 500 V DC overhead supply and the batteries were supposed to be recharged while traveling in the belowground development, they did non bear down up due to the presence of H2O. This challenge was overcome by redesigning the locos. The loco’s weight was increased for better grip and much larger capacity batteries were installed. Improvements to the pantographs design were made. The addition inefficiency and lesser loco dislocations made up for the corresponding addition in costs.

Another proficient challenge arose when the tunnels emerged from the resistance tunnels up to the surface about 900 meters short of the terminus at the UK side. This was resolved where applied scientists employed three different burrowing methods to finish the tunnels via the hard gault clay at Castle Hill. First, the NATM took the tunnel through the geologically ambitious strata at Castle Hill; while at either side of the hill, cut-and-cover building and top-down building were used. Cut-and-cover work involved unearthing the country and constructing the tunnel utilizing RC boxes. Top-down building (normally used in tight infinities) involved constructing the roof of the tunnel foremost before unearthing the land below it. The usage of 3 different methods of burrowing within a short 900 m stretch reflected the first-class technology constructs used in this undertaking.

Fourth, following the geophysical and geotechnical studies, the British anticipated that the dirt stratum was largely dry. They, therefore, configured the TBM in an unfastened manner. However, they tunneled into unexpected micro-fissured chalk which was permeable and rapidly incapacitated the TBM. Dry chalk started to give manner to moist chalk and balls of stones started to fall from the Crown and sides of the freshly excavated dullard. The circle was non sufficiently accurate from which the concrete liner could spread out. Work was so stopped to guarantee worker safety. Finally, the TBM was modified in situ. A series of dragging fingers were installed behind the cutting caput and spanned across the lap between the caput and the last subdivision of the liner. These fingers, when skidding frontward during drilling, restrained the chalk while at the same clip allowed the sections to be erected and grouted rapidly. TML besides applied extended sealing to the machinery and hosieries to forestall them from further seawater onslaught. Hence, the TBM started to do better advancement and the hold was minimized.

Other proficient challenges and inventions include the remotion of the TBMs that have completed the service tunnel. Stuck in the center of the tunnel and under the sea, these TBMs were not able to travel back up. While they could hold been taken apart and removed piece-wise from the tunnel, it was undesired as this would incur high costs. This challenge was overcome by driving one of the TBMs somewhat off the class of the tunnel and burying it into the chalkstone. In this manner, the other opposing TBM could drive frontward out of the tunnel. The British TBM was the one chosen to drive off-course and buried. After it drove into the stone, it was sealed away and the tunnel wall was covered with a concrete slab. The Gallic TBM was therefore able to travel frontward to the other side of the seashore and be removed. This building invention enabled the contractor to salvage costs.

For an undertaking of this mammoth graduated table, there was an edge to be budget overproduction and holds. The undertaking entailed designing; edifice and commissioning the full undertaking in merely seven old ages and being ready for opening in May 1993. This was non to be, as at the terminal of the undertaking, the estimated budget overproduction was 80% (entire undertaking cost making 9.2 billion) and the official gap of the Channel Tunnel was May 1994, one twelvemonth subsequently so the contractual completion day of the month.

One cause of the hold was due to the passing of the Parliamentary Bill which was required for the beginning of the plants. This was due to the objecting voices towards the edifice of the Channel Tunnel and the Bill could non be passed rapidly plenty. The hold took up most of the float that TML ab initio had and any farther hold could badly hinder the building agenda. To get the better of this trouble, TML started preliminary site plants like building the precast pace at the Isle of Grain and putting orders for the kinds of stuff even before the Parliamentary Bill was passed. It besides started a planetary hunt for manpower and technology endowments.

Another cause of hold during the early years of building on the Gallic portion was the fiscal prostration of one of the houses involved in constructing the TBM. However, the hold was reduced with the speedy mobilization of the TBM at the immense Sangatte shaft which allowed the 400T TBM organic structure to be lowered in one piece into the tunnel. On the British side, it was the unexpected moisture land conditions that caused the lag in burrowing plants and resulted in a hold of more than 3 months. However, the applied scientists modified the TBMS by putting inning the tracking fingers behind the cutting caput. Very shortly the TBMs started to drive at record velocities.

Third, the major cause of agenda hold was the difference between TML and Eurotunnel. The contractor’s claim that Eurotunnel owed it 1.45 billion; systems installed in the tunnel were the chief cause of the difference. This figure was more than twice the figure stated in the Contract, which Eurotunnel insisted that the amount owed was less than 900 million. The drawn-out legal conflict between the two entities delayed the undertaking. TML decided to finance its ain plants while Eurotunnel sourced for finances, which potentially would force the undertaking completion day of the month further back. In the terminal, Eurotunnel struck a trade with TML where TML would necessitate to hit a series of mileposts over the months in 1993 to hand over the undertaking to Eurotunnel by Dec 1993. In return, Eurotunnel would give a beforehand payment of 235million to TML so that the latter would non run out of finances. This inducement enabled TML to force for advancement and minimize hold.

There were a few causes of budget overproduction. First, the original start to completion continuance was a mere 7 old ages, significance that the undertaking had to travel from design development to completion in that length of the clip. As a consequence, many design jobs (e.g. unfastened manner TBMs used by the British) were non-identified and resolved at the start of the undertaking, and no commissariats were made for these commissariats in the initial cost estimations. Eurotunnel, therefore, had to begin for extra finances for the undertaking.

Second, due to the competitive nature of the undertaking, CTG/FM had to cut their cost estimations to the bare lower limit to do a successful command. This was made with the cognition that the voting pool would be evaluated on fiscal standing – therefore the principle for taking downing the net income borders. The subsequent cost addition was blamed on holds from the parliamentary procedure and early funding jobs.

Third, the budget overproduction was caused by the addition in costs and figures of kinds of stuff required for the undertaking. Even though TML had planned to line the tunnel with dramatis personae Fe sections instead of concrete in the wetland as they were more watertight, they had non expected the UK TBMs to besides hit hapless land ( contrary to geotechnical analysis consequences ). The needed sum of dramatis personae Fe had already exceeded the entire sum of dramatis personae Fe originally estimated when this happened and cost addition was inevitable. TML tried to cut down costs by rushing the tunneling procedure and modifying the TBMs.

While the undertaking was delayed many times due to boardroom differences and unexpected site conditions, advanced thoughts were put into a pattern that helped to increase productiveness. For case, due to the hapless land conditions and H2O immersion at the UK side, TML had wanted to utilize cast-iron liners which at that clip were already over-budgeted. However, advanced thoughts led to the alteration of the tunnel liners, known as intercrossed liners where countries of high emphasis would be taken by the Fe while the majority of the run a longing ring was still made of concrete. Not merely did these liners save TML near to 20 million, it besides reduced three months on the critical way. In add-on, betterments and alterations to the TBMs were made, their lining erectors and spoil remotion systems extensively changed, their electronic systems simplified and waterproofed. The TBMs ‘ public presentation improved enormously and shortly they were interrupting universe records for burrowing rates. Miners and workers were besides incentivized for good work advancement so that their morale remained high. Their wage was reviewed to stay market-competitive. Eurotunnel besides formed a policing arm known as the Project Implementation Division to maintain cheques on the building advancement and on TML to make more to remain on the scheduled timetable.

The entire decease toll for this undertaking was increasing at a dismaying rate towards 1990. Safety at the building sites was put under intense examination. This prompted TML to encompass DuPont’s safety patterns and rules and made a few inventions to its safety program. First, a series of chiefly one-to-one audits were carried out by the chiefs and supervisors on the workers at work. These were no-risk audits, and the auditee was encouraged to state the hearer of his ascertained actions that were less safe than coveted and was besides encouraged to do safety suggestions. Completed audits placing the hearer ( but non the auditee ) were analyzed by a senior line director and summarized for the local line director to place tendencies and program follow-up actions. As a consequence, many antecedently unidentified safety issues were found and later resolved or mitigated. Second, safety awards were awarded, through a lottery, to persons or squads of forces who managed to accomplish 25000 accident-free work activities. Third, posting runs were carried out to turn to safety issues such as path safety and proper PPE. These runs were complemented by other signifiers of media such as safety notes in payslips, on-site picture presentations, and toolbox briefings to all employees. These safety patterns resulted in zero deceases for the following two old ages of building.

To reason, the Channel Tunnel was a gigantic privately-funded undertaking in its ain right. It was of no average effort for the completion of an undertaking affecting 2 states separated by a sea 34 km long and both being traditionally challengers. Even though it was completed a twelve-month tardily and at least cost overproduction of at least 80 %, the Channel Tunnel can still be considered a success, this in position of the direction, proficient and funding challenges faced by the parties throughout the undertaking. Apart from the celebrated senior direction conflicts and arbitration between the proprietor and contractor, it must be noted that the direction and proficient inventions led to an addition in productiveness and should be used as a mention for future undertakings.

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