The proposed design of the English Channel Tunnel

The Proposed Design of the English Channel Tunnel* C. J. Kirkland

Abstract--This paper gives an overview of the history of the development of a fixed link across the English Channel, including reasons why the project is now going forward. The article provides an analysis of projected traffic volumes and revenuesfrom the Channel Tunnel, as well as a description of the tunnel scheme proposed by the Channel Tunnel Grvup/Franee Manche (the English~French partnership commissioned to design and execute the projecO. Engineering concepts and design, contractual arrangements, and financing issues are also discussed at some length in the article.

Introduotlon or more than two thousand years, Britons have been grateful for the various stretches of water that separate us from mainland Europe. It has given us a sense of security, though it has been breached many times, by Romans, Saxons and others. With the end of the Napoleonic wars at the beginning of the last century, and the rise in importance of Britain in that century, many have dreamed of constructing a fixed link with France. The first really positive move was made in 1882, when the First Channel Tunnel Company was formed and applied to the British Government for permission to construct a railway to France by means of a tunnel. Subsequently Colonel Beaumont of the Corps of Royal Engineers designed a rotary boring machine, with which he actually bored over a mile of tunnel extending out under the foreshore. The sad remains of this machine can still be found near the tunnel portal, and his unlined tunnel bore remains to this day. Interest in the project re-awakened after the Second World War, and in 1956 a Channel Tunnel Study Group was formed. A considerable amount of geotechnical investigation was carried out in 1964-65, as a result of which a feasible alignment for a bored tunnel link was established. The latter took advantage of the natural geological formation existing beneath the bed of the channel. In 1971 the governments of Britain

F

*Acknowledgement: This article is based upon a paper given to the JTA/ITA Japan Colloquium on Undersea Tunnels in March 1986, supplemented by further information provided by Eurotunnel. Mr Kirkland is recognised a fellow of the Institute of Civil Engineers (F.I.C.E.), Chairman of the British Tunnelling Society and Technical Director of Eurotunnel. Present address: Eurotunnel, Portland House, Stag Place, London SW1E 5BT, U.K.

and France decided to commence construction. Work began on the access tunnels in both countries, and on the main pilot tunnel on the British side, before this attempt was aborted in 1974 due to escalating costs and political problems. In 1985 the combination of improved political relations between Britain and France, and strong governments committed to private enterprise, led to agreement between them to issue a public invitation for proposals in April. The basic guidelines to which proposers had to adhere were: • The link was to be "fixed". • It was to be totally privately financed. • There would be no government guarantees. • Proposers had to demonstrate that their scheme was robust both as to technical feasibility and financial return to investors. As a result of this invitation, four acceptable proposals were submitted: (1) A bridge of 5-km spans with a totally enclosed multilane roadway (Eurobridge). (2) A system of 0.5-km span bridges from shore to two artificial offshore islands upon which spiral ramps would be constructed to carry the roadway down to an immersed tube tunnel linking the islands across the main shipping lanes (EuroRoute). (3) A pair of parallel 11-m-diameter bored tunnels carrying both roadway and a railway, incorporating artificial islands to permit ventilation shafts to be built to serve the tunnel (Channel Expressway). (4) The 1972 scheme comprising two 7.3-m-diameter bored railway tunnels, with a third 4.5-m-diameter pilot tunnel parallel and between them to provide emergency and other services. The railway tunnels would provide a "rolling road" of rail mounted shuttle cars, with facilities for through passage of the ser-

Turm.dling amt Un&TgroundSpace Technology,Vol. 1, No. 3/4, pp. 271-282, 1986. Printed in Great Britain.

R~,sum~---Cet article prlsente une vne glnlrale de l'histoire du dlveloppement d'un lien permanent fi travers la Manehe ainsi qne les raisons pour lesquelles le profit est dlsormais en cours. On analyse les volumes de traffic et les bln/flees projetls et on donne une description du tunnel tel qu'il a itl proposi por le groupe Channel Tunnel Group~France Manche (les partenaires anglais et franfais disignls pour concevoir et exlcuter le proje O. Les concepts techniques, la conception, les arrangements contractuels ainsi que les issues finaneikres sont amplement discutles.

0866-7798/86 $3.00+.00 ~) 1986 Pergamon Journals Ltd.

vices of both National Railway companies, British Rail and Soci6t6 Nationale de Chemins de Fer Fran~;ais. The approximate line of this scheme is shown in Fig. 1.

A Channel Fixed Link: Why Now? The creation of a fixed link to cross 22 miles of sea is not a venture to be entered into lightly, even if the cost is to be met from the public account, and the eventual facility seen as an essential part of a country's infrastructure whose people as a whole will benefit. In the United Kingdom the whole of the existing railway network was constructed by private railway opeators, who sought and obtained government permission to construct railways in response to a forecasted growth of private and commercial traffic. The proposed Channel Tunnel is similar in many aspects. The volume of traffic which crosses the English Channel each year grows steadily, and with the continuing development of the European Economic Community seems set to continue. Why is it now considered desirable to build a fixed link across the Channel? • Passenger and goods traffic between the U.K. and the Continent has been increasing in recent years and this trend is expected to continue. (Europe is Britain's major trading area; in 1984, 64% of U.K. exports of goods and services, excluding oil, were to the EEC.) • The existing sea ferry services and the already congested sea lanes of the Channel will be unable to accept this increasing traffic burden. • Modern technology has made it possible to build the Tunnel quickly and to establish a modern shuttle system to transport passenger cars and commercial vehicles efficiently across the Channel, providing a competitive addition to existing modes. • The Tunnel will be able to accommodate through train services 271

X\ Deal

XXX\\

Cheriton

Cl,iff

'~'~ ,~ '%~,,%, Proposed tunnel [ink

Fotkestone

""

Dover straits

i//

. IL)7,

\"

Figure 1. Plan for the proposed Channel Tunnel Link. operated by the U.K. and French national railways. • The British and French Governments are strongly in favor of a fixed link. • The Banking Group Study published in 1984 demonstrated that the Tunnel scheme can be financed and built privately, without recourse to public funds. • The construction of a fixed link will give a stimulus to employment and trade, particularly in the economically depressed area of the Pas de Calais.

Analysis of Traffic Volumes As part of the 1985 submission to the governments, a comprehensive study into the likely traffic volumes and revenues from the Channel Tunnel was carried out by leading consultants SETEC 6conomie and Wilbur Smith & Associates. The evaluation was carried out in three stages: (1) Analysing existing cross-Channel traffic and its recent evolution; (2) Establishing the size of the total market for each category of crossChannel traffic and determining the percentage of each category likely to divert to the fixed link; and (3) Estimating the amount of n e w traffic that will be generated by the existence of the fixed link. According to the research carried out, cross-Channel traffic grew between 1977 and 1983 at an annual rate of 7.9% for passengers and 4.5% for freight, so that

Table 1. Cross-Channel traffic volumes, 1977-83.

Traffic In 1983 Annual Growth (In millions of u n l t s ~ 1977-1983 Passenger Car

6.7 6.1 2.6 30.6

Coach

Excursionists by coach (special tariff) Other foot passengers (incl. air)

Total

46.0

7.9%

Freight (tonnes) Ro-ro Containers Wagons Bulk (incl. new vehicles)

17.7 4.6 1.1 30.0

Total in 1983 the level of traffic was as shown in Table 1. In the analysis shown in Table 1, cross-Channel traffic is defined as those journeys between the U.K. and countries in Western Europe. The principal modes of travel are sea ferries, hovercraft (Dover straits) and air. With regard to sea journeys, the area covered ranges from the Western Channel (South Coast of EnglandNormandy) to the Southern North Sea (East Anglia-Netherlands/Germany). Within these corridors, freight traffic is fairly evenly spread, the Southern North Sea sector having the largest share at 43%. Passenger traffic, however, is very much concentrated in the French/ Belgian straits area, which accounts for

272 TUNNELLINGAND UNDERGROUNDSPACE TECHNOLOGY

53.4

4.5%

74% of passenger traffic carried by sea. Using the consultants' central case forecasts, future traffic demand and Tunnel share are forecast as shown in Table 2. Figures 2 and 3 show the projected total market and Tunnel shares in chart form. For the ten-year periods up to 1993 and 2003, this represents an annual growth rate of 3.9% for passenger traffic (both periods) and 3.3% and 4.3% growth rates for freight (see Table 3). It is anticipated that 9% of the passenger traffic will be new business, generated by the existence of the new facility.

Projected Revenues It will be the operator's policy to adopt tariffs which match those that are

Volume 1, Number 3/4, 1986

Table 2. Projected traffic demand and Tunnel share. 2OO3 1983 1993 Total Tunnel Total Total Tunnel demand demand ,here demand sham P ~ a e n g e r a (m.) Car pe&sengers Coach p ~ e n g e r s Excursionists (coach) Other foot passengers

(incl. air) Additional rail passengers

6.7 6.1

9.6 8.4

6.3 4.4

11.9 11.7

7.3

2.6

3.2

3.1

3.5

3.4

30.6

46.1

10.9

71.5

12.9

with high speed trains

5.5

5.0

Total Freight (m. tonnes) Re-re freight Containers and rail wagon Bulk (incl. new vehicles) Total

7.9

46.0

67.2

29.7

98.6

37.0

17.7 5.7 30.0

24.2 7.9 41.8

6.0 4.0 3.2

35.2 12.7 64.5

7.5 6.8 4.6

53.4

73.9

13.2

112.4

18.9

Passenger traffic (miLtions per annum) 80 7O 6O

~_ 50 o

4o

Air

Air

3(3

Surfoce

Surfoce

20

++++++++++++ I++++~i/++++ + ++ ++++++v+T+' :++++++++ + l +

I0-

Surface 0 1983

Surface

i.++++÷-~¥++++ ~I 1993

2003

Foot : w i t h o u t

1983

1993

2003

Foot :with TGV

TGV

expected to be offered by their major competitors after the Tunnel is opened. Assesments have been made of the lowest tariffs currently available; these are not brochure prices but, rather, charges net of the substantial commissions and discounts offered by the air and ferry operators. It is further assumed that: • the ferry operators will cut these lowest tariffs by an additional 10%; and • air fares between London-Paris/ Brussels/Amsterdam will be cut by 20/ 25/10%, respectively, once the Tunnel is opened. These discounted and reduced tariffs are built into the traffic and revenue forecasts (see Table 4; figures are expressed in sterling at 1985 prices). Figure 4 shows the total projected revenues, divided into passenger, road, rail and freight traffic revenues. Figure 5 outlines the length of a typical journey between London and Paris, and compares the current forms of transport with the projected time required using the proposed Channel Tunnel. The points to note here are: (1) On the shortest ferry r o u t e - between Dover and Calais--the journey time is about 1 h 15 min to 1 h 30 min, with other formalities adding a further hour or more. (2) Journey time for the hovercraft is much shorter--only 35 miD; but, again, formalities can add a further hour. (3) Both of these services are vulnerable to adverse weather conditions; a tunnel would not be. (4) With the French High Speed Train operating, the journey time using the Tunnel will be 3 h 15 rain, which is competitive with air services on a city centre-to-city centre basis. Even with conventional trains, the journey time should be reduced from the present 6 h 20 min to about 4 h 30 min.

o I0 0 1983

~++++++++++÷ ~++++++++++~ 1993

2003

1983

Car

1993

2003

Coach (incLuding excursions)

I00 90 80 70 ~= 6O o 50

40 30 20

- -

I0 0 1983

With TGV

~ ~

Without TGV

~+++++++++++ ~+++++++++++ +++++++++++ +++++++++++ p++++++++++~ 1993

2003

Totat

Figure 2. Projected total market and Tunnel share of passenger trajOfc, 198.3-2003.

Volume l, Number 3/4, 1986

Proposed Mode of Transport

Channel Tunnel Group~FranceManche (CTG/ FM) The C T G / F M scheme consists of two single-track railway tunnels, each with a diameter of 7.3 m. There will also be a 4.5-m service tunnel between the railway tunnels to provide for ventilation, maintenance and safety. Tunnel length will be approx. 50 kin, of which 37 km will be below the sea. The Tunnel is due to commence operations in spring 1993. Operations. Roll-on/roll-off shuttles, capable of carrying all kinds of vehicles (cars, coaches, caravans and commercial vehicles), will operate between the two terminals. Initial demand will probably be for about 1000 vehicles per h, but the Tunnel will be capable of handling over 4000 vehicles per h in each direction with shuttles leaving, at peak times, as frequently as every 3 min. (This capacity is higher than that of an ordinary two-lane motorway.)

TUNNELLING AND UNDERGROUND SPACE TECHNOLOGY 273

Freigh± t r a f f i c (miLLions of tonnesper annum) 80 70

6O 4w

g

50 40

30 2O I0 r - ~ - r t-e-i- -i- + + + + + -

~+++++++++++

IF+++++++++++t

0 1983

1993

IF+++++++++++I

200:5

1983

Ro-ro freight (excLuding containers, bu kk and new vehicles)

199.3

200.3

Rail freight (i nctuding containers, bulk and new operations)

I00

90 80 7o E c g

60

Journey time between terminals, with shuttles travelling at a maximum speed of 160 kph, will be approximately 35 nlin. No reservations will be necessary; users will buy their ticket and go through customs/immigration facilities before boarding the shuttle. There will be no formalities on exit. Passengers can either stay in their vehicles or walk around the shuttle to take advantage of refreshments and other facilities. Hence, it will be a fast, relaxing and safe means of transport. The Tunnel will operate 365 days a year, without disturbance from the weather. Through train services of British and French National Railways will also be able to utilise the Tunnel, and there is the possibility of French high-speed trains operating through to London (running at normal speeds in the U.K.). Suitable trains will be designed, compatible with Tunnel specifications. Including this through rail element, the Tunnel will be capable of handling 20 trains per h, initially. Total costs of the scheme: £2.7 billion (in 1985 prices).

~n 50

g_

Provision of a Link

40 ~

Tunnel share

30

~ + 7 +

20

+.

i+--q- + + + + + + + + + i+++++++++++_ |+++++++++++-

10 o

I+++++++++++t f993

1983

2003

Total freight

Figure 3. Projected total market and Tunnel share orfreight traffic, 1983-2003.

Table 3. Annual growth rate in traffic demandfor 1983-1993 and 1993-2003.

Traffic forecasts

Annual growth rate 1983-1993 1993-2003

Passengers Freight

+3.9% +3.3%

+3.9% +4.3%

Table 4. Projectedrevenuesfrom cross-Channel traffic in 1993 and 2003.

Central case (1985 prices) 1993 Car passengers Coach passengers Rail passengers Rail freight Roro freight Ancillary (incl. duty free)

£m

2003

124.2 35.8 86.2 46.9 60.4 35.7

140.4 42.5 102.8 77.7 75.5 41.7

389.2*

480.6

*annualised

274 TUNNELLINGAND UNDERGROUNDSPACE TECHNOLOGY

As has already been outlined above, such a link has been under consideration for very many years. Despite this, the present plans for the link must be governed by the Invitation to Promoters (issued in April 1985), which set a new scenario---total private financing. The Channel Tunnel Group/France Manche proposal was rapidly drawn together, based upon the 1973 scheme, by a group of contractors who had kept the scheme alive over the intervening years. This Anglo-French contractor grouping, whose primary interest was the construction work, was joined by two British and three French banks. Together they have created two "owner" companies, one in the U.K. and the other in France. The proposal to the two governments was made jointly by a partnership of these two owner companies. They have contracted for the design and construction of the proposed link with a joint venture comprising the Anglo-French Contractor Group. A further requirement of the Invitation to Promoters was the employment by the promoter of an independent "project manager" to be responsible for providing assurance to both governments and investors of the technical and financial viability of the project. To meet this requirement, a group of international consulting engineers has been appointed, with terms of reference similar to those of maftre d'eeurre in French construction practice.

Volume 1, Number 3/4, 1986

Passenger 63 %

Road 5 9 %

Rail 3 4 %

Year

Total

1993

~.389.2 m

Freight 28 %

Speed. The speed of a train is controlled and subject to defined parameters; the speed of a "drive-through" crossing would be related to the speed of the slowest driver. Therefore, the rail crossing will be faster. Finance. Because the tunnel uses proven technology and anticipates generally favourable geological conditions, reliance can be placed on the cost estimates and programmes. This factor, added to the relative cheapness of the scheme, makes it an attractive financial proposition. Traffic. Using shuttle trains, the tunnel has an ultimate capacity in excess of a two-lane motorway, i.e. the rail tunnel is very efficient in terms of throughput against tunnel diameter. Ventilation. To operate a tunnel of this length with anything other than electrically operated trains necessitates a very expensive and extensive ventilation system.

Passenger 59 %

Description of the Proposed Tunnel The tunnelling works for the Tunnel embody the following features travelling from the U.K. to France:

Cor

Rail passenger

Rail 3 8 %

[

Road 5 5 %

J AnciLLary Coach

Rail freight Ro- ro freight

Year 2003

Total ~480.6m

Freight 32 %

Figure 4. Projectedtotal revenuesfrom road, rail andfreight traffic (expressedin sterling at 1983

prices).

Engineering Concepts Choice of Concept A detailed engineering and financial appraisal of a number of tunnel schemes was carried out prior to submission of the rail shuttle scheme in order to ensure that a viable offer was made. We concluded, as others have in the past, that a rail shuttle scheme was the only feasible choice under the government guidelines, which insisted upon a feasible, financially robust proposal. The reasons for our conclusion involve considerations of safety, reliability finance, traffic, and ventilation. Each of these is discussed below. Safety. In a transportation route of up to 50 km in length there are considerable hazards. These can be lessened by con-

Volume 1, Number 3/4, 1986

• Twin 7.3 m-diameter tunnels through Castle Hill for a length of approx. 515 m. A 4.5-m service tunnel runs between these for a length of 200 m to comply with safety access requirements; • A 650-m length of cut-and-cover box section tunnel to carry the railway between Castle Hill and Holy Well on twin tracks; • Single-track tunnels of 7.3-m diameter spaced 30 m apart with a 4.5 m-diameter service tunnel positioned centrally between them, running from Holy Well to Beusingue Farm near Sangatte. The tunnels cross beneath the Channel from Shakespeare Cliff to Sangatte. Other features are:

veying people and their vehicles in shuttle trains which are controlled by trained staff and run in a controlled environment. (Private motorists have proven on numerous occasions that they cannot be trusted to abide by safety rules and signs.) An emergency situation can be coped with in a controlled and safe manner, an all-important criterion in a tunnel. Reliability Breakdowns. Trains running as a shuttle such as is proposed can provide a reliable, predictable service. This could not be said of anything which involves road transport. For example, the Dartford Road Tunnel under the river Thames in London recorded 359 breakdowns during 1983, i.e. an average of one per day.

• Cross-passages of 3.3-m diameter which are required for safety and operational reasons to connect the railway tunnels and the service tunnel at 375-m centres; • Piston relief ducts of 2-m diameter to reduce aerodynamic drag on the trains connect the railway tunnels at 250-m centres; • Full-section cross-over tunnels which connect the railway tunnels, located at approximate chainages 25 and 47 (measured in km from the British terminal); • Drainage sumps to collect seepage water at the low points of the tunnel profile; and, • Adits and niches for underground electrical equipment and catenary tensioning devices.

TUNNELLINGAND UNDERGROUNDSPACE TECHNOLOGY 275

Seo

-ferry

Hovercraft

Air Train/metro Transfer |~:..'::':~::'::'::':i~:~:~:t FormaLities I I Crossing/fLight l~/////f//J

Channel Tunnel

I

I

I

I

1

I

I

L

J.

h

0

I

2

3

4

5

6

7

8

h Figure 5. Comparison of lengths of a typical journey between London and Paris, by sea ferTy, hovercraft, air and the proposed Channel Tunnel. Ventilation Ventilation requirements are not onerous. The most important aspect is the provision of a fresh air supply to the service tunnel because in emergency conditions, this is the place of safety. There is, in addition, an obvious requirement to provide a satisfactory working environment for all personnel working in the tunnels and crosspassages. Our system for normal ventilation is, therefore, based on pressurising the service tunnel and allowing air to exhaust from the railway tunnels. Emergency ventilation or smoke extraction is also required in the railway tunnels for emergency situations.

Engineering Design Basic Arrangement The basic design concept (Fig. 6) provides for twin 7.3-m tunnels with a service tunnel positioned centrally between them, bored through the lower chalk marl. The service tunnel, which is required to locate services as well as for safety purposes, is driven as a pilot in advance of the main bores. Its size is governed by: • • •

Construction phase transport vehicles. Operation phase transport vehicles and safety requirements. Sufficient space for the installation of fixed equipment.

The size of the main bores (7.3-m internal) is governed by (cf. Fig. 9): • •

The loading gauge of the rolling stock (5.24 m) The minimum height necessary for track bed construction.

• •

Clearances for the catenary equipment. An all-embracing construction tolerance of 300 m.

C~oZo~ Site investigation for the Channel Tunnel has been going on since as long ago as 1865, when Sir John Hawkshaw carried out some boring in St Margaret's Bay and some samplings at sea. In more recent times the Channel Tunnel Study Group carried out a study (1958-59) that included marine borings, a geophysical survey, and sea-bed sampling. A major site investigation was then undertaken in 1964-65, including nearly 100 marine boreholes and 20 land boreholes, in-situ and laboratory testing of the rock, and a thorough seismic survey at sea. This formed the basis for the 1973 R.T.Z. Proposal. Further investigation was included in Phase I of the 1972-74 works; 7 additional inshore boreholes and 15 marine boreholes were sunk and a geophysical survey of areas where specific problems had been encountered during earlier work was carried out, together with a survey of part of the route near the British coast that was previously unsurveyed. Further investigation has been provided for in our proposal. Briefly, the geology of the strait comprises chalk layers overlying Gault clay and Greensand (see Fig. 7). On the U.K. side of the Channel some folding is evident, but this is quite gentle. On the French side, however, it is more folded and complex. There are three principal strata along the chosen route of the tunnels. In descending order, these are: Middle

276 TUNNELLXNOAND UNDERGROUND SPACE TECHNOLOGY

Chalk, Lower Chalk and Gault Clay. The Middle Chalk and upper portion of the Lower Chalk comprise relatively brittle fractured chalk. The lower part of the Lower Chalk comprises a combination of clay and chalk distinguished as Chalk Marl. Chalk Marl provides a moderately strong, uniform and slightly plastic material generally free from open discontinuities, making it a virtually impermeable stratum, ideal for tunnelling. The Gault Clay, while also impermeable, is weaker and exhibits strongly plastic behavior, leading to nonuniform deformation when stressed. The tunnel alignment, subject to operational and performance constraints, has been developed so as to locate the maximum length of the tunnels within the most favourable medium (the Chalk Marl) whilst minimising, wherever possible, the incidence of disturbed or unfavorable ground conditions. Sections of poor ground are anticipated: to allow for these, probing ahead of the tunnel face will be undertaken and modified tunnel linings will be provided (see discussion below). The features which could give rise to tunnelling problems are fissures and faults. Fissures will increase the permeability of the ground and could cause delays due to increased water seepage. Faults could also cause increases in permeability--either by seepage down the fault plane or by fissures in the disturbed ground adjacent to the fault: However, indications are that there will not be problems of face stability, and that erosive action by permeating water is unlikely. Furthermore, there is no evidence to suggest the existence of any major longitudinal dislocations within the chalk, nor

Volume i, Number 3/4, 1986

15.00m

15.00m

The spoil will be removed from the closed face machines hydraulically, as a mud slurry. Treatment stations for this removal will be positioned at the tunnel access point.

I

i

i

Concretesegment Safety door

Cross passage

L/

Spoil Disposal

7.3m Internal diameter railway tunnel

~ ~

7.3m Internal diameter railway tunnel

4.5m Internot diameter service tunnel

Figure 6. Tunnel cross-section. of any faults with displacement or "throws" greater than 15 m. The faults thus far identified appear to be generally sub-vertical, although subparallel faults with minor throws have also been identified in local areas (see Fig. 7).

Probing Ahead An important area in the development of our proposal to date has been the consideration of the risk of unstable ground or areas of very high permeabilities. Minimisation of these risks will be achieved by probing ahead of the service tunnel on a regular basis and always maintaining at least 20 m of "probed" ground ahead of the face. Probes will be up to 100 m long and drilled ahead and slightly upwards of the face, vertically downwards to locate the Gauh clay layer, and laterally to the railway tunnel locations (see Fig. 8). Once an area of instability of high permeability is identified, it will be treated using a rapidsetting cement grout.

Tunnelling Method To justify necessary financial confidence to be placed in the scheme as a whole, the methods proposed have been developed from tried and proven techniques and previous experience, including experience of group companies in the length of service tunnel constructed in t974/75. Since then, full advantage has been taken of developments, but no attempt has been made to break new frontiers in either construction techni-

ques or technology. Cost estimates and programme times, therefore, can be viewed with some confidence. The tunnels will be driven from two sites, one in the U.K. and one in France. One each side, the tunnels will be driven from a working site located adjacent to the coast. In all, 11 tunnel boring machines (TBMs) are expected to be used. The U.K. tunnels will use the open-face type machines; the French undersea tunnels will use convertible machines (from pressurised to openface); the French underland tunnels will use the closed-face pressurized type slurry machines. Boring of all tunnels will proceed in parallel with the exception of the French underland section, for which the railway tunnel TBM will bore these relatively short tunnels sequentially. The open-face TBMs will be equipped with conventional back-up systems for spoil removal, segment handling, grouting, fixing of temporary services, etc. Spoil transport from the face to the disposal point will be by electric construction locomotives hauling muck wagons and, also, segment cars and personnel cars. Temporary double track will be placed throughout the tunnel for this purpose. The tunnelling is programmed to proceed on a 24-h, 7-day basis, with interruption of work for statutory holidays only, and working four 6-h shifts per day. Of these 28 weekly shifts, up to 7 will be reserved for probing (as described above).

The tunnelling work will yield approx. 6.5 million m s of spoil---4 million m s on the U.K. side and 2.5 million m 3 on the French side. Spoil will be utilised depending upon where it arises. At Holy Well, U.K. all spoil arising (1.1 million m 3) will be placed on the terminal site as fill. At Shakespeare Cliff, an area of land reclamation is proposed to produce a larger working site, necessary for the efficient servicing of the tunnelling works. At Sangette, France, spoil arising as slurry at the head of the "Descenderie" (inclined adit) will be placed in a slurry separation pit on the adjacent Fond Pignon area, and the solid spoil will be transported from the "Descenderie" to the terminal site. By arranging to handle disposal/ utilization adjacent to the point where it arises from underground, the environmental problems connected with the transportation of spoil have been minimized.

Linings A number of lining types have been developed (see Fig. 10) to suit the ground conditions and the construction methods envisaged. Most of the U.K. section will be lined with precast concrete expanded-type linings, varying in thickness to take into account the different loading conditions. Although this procedure will involve a varying internal diameter, it offers significant financial savings for tunnels of such length (see Fig. 9). Where less favourable ground conditions are encountered, or an impermeable lining is required, or at junctions, nodular iron bolted linings have been designed. In the French section, the more locally varied nature of the ground conditions have led us to propose a heavy-duty precast concrete bolted lining throughout.

U.K.terminal UpperandMiddleChaLk J ~ h CastLeHiLL HaL akespeareCliff

~

~

Frencht,ermlnal.

L~eLC~_~

/ ~ ~

M,ddleChalk

GauLt C ChaLk Marlf Green Sand

Figure 7. Geological section of the tunnel route.

Volume l, Number 3/4, 1986

TUNNELLING AND UNDERGROUND SPACE TECHNOLOGY 277

~ ~ ' - - - .

Note I 2N°probesxlOOm tongat 5°offset to both horizontal and vertical planesare driven every 75m, leaving a minimum coverof 25m Side probesare driven every 500m

-~--. ~'~

<..

Z \ Figure 8. Planned probing from the service tunnel. Space for overhead fine and pantograph

~ CooLing pipes, cable

and LiGhting

Shuttle train

racks '

~

Tunnel Lining

SNCF/UIC SNCF/L IC

~

~ B r i t i s h

Standard track gouge

rail

London transport

1.432 m (4" 8 ~z'

"U nderground"

Figure 9. Rail structure gauges. Drainage On the basis of an assessment of the permeabilities measured in the boreholes along the route, the water inflows into the tunnels have been predicted. The profile produced by following the Chalk Marl layer has four low points; provision has been made for collecting sumps at these points so that the water can be pumped to the surface. Sumps have been designed not only to cope with the normal inflow expected, but also to cope with emergencies such as pump breakdown, burst drainage, or cooling water pipes and fire-fighting water.

Ventilation N o r m a l ventilation. Each tunnel section half will be supplied with ventilation air from the British and French coasts. On the French side, a ventilation plant room is located at the top of a 3.6-m-

diameter shaft connected to the service tunnel. On the British side, the ventilation plant building is located at the entrance of an inclined adit at the lower Shakespeare Cliff, which connects with the service tunnel. Railway tunnels will be ventilated by air flowing down the service tunnel and through each cross-passage. Dampers which control the air flow into the railway tunnels are fitted to each crosspassage door to achieve a regular distribution of the air flow along the 25 km of each system. An airtight door situated at the mid-point of the service tunnel will separate the two systems. Emergency ventilation. In an emergency situation, separate ventilation shafts and equipment at each coast can supply fresh air directly to the railway tunnels; or, by reversing the fans, smoke and fumes can be extracted.

278 TUNNELLINGAND UNDERGROUNDSPACE TECHNOLOGY

Contractual A r r a n g e m e n t s

(see Fig.

11) The brief description of the basic outline of contractual arrangements given above (under "Provision of a Link") does not disclose the complexity of the total scheme. It is probably fair to say that the time-scale forced upon the promoter by the twin constraints of eventual economic viability and the U.K. democratic Parliamentary system have brought about the ultimate in "fast tracking." Under normal circumstances, the promoter of a scheme would define the objectives, outline the project, obtain necessary authority from the government, invite tenders for design and construction against a prepared form of contract, and enter into a contract--in that sequence. Because the promoter has no source of income until the project is commissioned, the earliest commissioning date controls the entire process. In this case, until the date on which the two governments gave their approval to the selected scheme, all design development was not only speculative, but--even if selected--depended upon the limits of the concession ultimately granted. Neither negotiations on the concession nor work on the enabling Bill to be placed before the U.K. Parliament could begin in earnest until the preferred scheme had been identified.

Volume 1, Number 3/4, 1986

A Service tunnel Railway tunnel

ELevation B-B

Section through Circumferential joint

C

BL_

_jB Section A - A radial joint

LC

C-C

Figure 10. Tunnel linings for the service tunnel and railway tunnels.

France

U.K. J Government

J Government

Treaty

J

0

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ol

Ul

Channel TunneL Group

[Finance J I I

J I j

J

I

I

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I l I

J J I

Maitre d'oeuvre

J consultant Audit

I

U.K. contractor

France Manche

Design and construct contract Joint venture tronsmanche Link

French contractor

I

Programming

Figure 11. Overall organization structurefor the Channel Tunnel Project. The Invitation for Proposals required that proposals be accompanied by a reasonable cost estimate, and by some form of commitment from banks and other possible lenders and investors to providing the necessary funding. Thus, the contractors were obliged to prepare a cost estimate before the project was defined and the conditions of contract established.

Volume 1, Number 3/4, 1986

link concept has been kept alive over the years since 1973 by a small group of contractors. Much of the funding which permitted the present scheme to be prepared for submission in October 1985 was provided by this same group of contractors, who also formed the Promoter Group. It is, therefore, not surprising that this same group of contractors should expect that the work of construction of the link should fall to them. The construction contract will, in fact, embrace the whole of the design and construction of the proposed link, and the procurement of the specially designed rolling stock and locomotives. However, such a mammoth project carries such a large volume of risk of one kind or another that the sharing of that risk is of more than usual importance. The sheer size of the project, and the refusal of either government to provide any kind of financial support, also presents a problem of capability to spread the risk. Basic sharing of risk within the contract is achieved by subdividing the work into three separate streams: (1) The design and construction of the terminal facilities and other fixed equipment, covered by lump sum contractual arrangements. (2) The design and construction of the tunnels, covered by target cost contractual arrangements. (3) The design and construction of locomotives and rolling stock, covered by procurement arrangements within a budget provision. The construction contract will be directed by the promoter's engineering teams, who will require the contractor to provide details of programme and forward cost estimates, safety and quality assurance procedures, etc. Management of the project will be the responsibility of the contractor, along similar lines to those envisaged by the FIDIC form of contract, although there will be no designated "Engineer". Monitoring of the contractor's performance will be carried out by the maitre d'~uvre, who has been appointed by the promoter. The maitre d'eeuvre's task will include a responsibility to the lenders of funds and to the governments, as well as to the promoter.

.In order to keep within the construction time-scale offered, and to have the enabling Act passed by the U.K. Parliament before the next general election, the owner has had to perform the various functions listed at the beginning of this section simultaneously instead of in sequence, and has had to accept the risks inherent in such a process (see Fig. 12). As noted above, the rail tunnel fixed-

The overall project programme for the Channel Tunnel Project (depicted in Fig. 13), is expected to cover a total design, construction and commissioning period of seven years, with the first operation aimed at meeting the peak summer season demand for passages across the Channel in 1993. The construction programmes in England and France are expected to commence at dates approx. 12 months apart. This situation is forced upon the

TUNNELLING AND UNDERGROUND SPACE TECHNOLOGY 279

ChanneL Tunnel

Master programme b o r c h o r t

1986 l r Jz13141~161?le19

I p 1987 IoJnl4z113}i41 i5116li7 IlSllel2Olzt 2 21,~11241~612"~1~1301311321~1

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1993

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16 I Construction (France) 21

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Figure 12. Master programme bar chartfor the Channel Tunnel Project: control dates, construction and commission of the project. Promoter by the differing political systems in the two countries. The French are able to commence almost immediately following upon a Presidential Decree, whereas the British must follow a very delicate and protracted parliamentary process. The construction programme itself is, of course, governed by the speed at which the tunnels themselves are constructed, with some early linkage between the recovery of spoil from the tunnels and the basic earthworks for the terminals. Final commissioning will later be controlled by the installation of fixed railway equipment and signalling and other train control systems. The financing programme is, of course, tightly geared to the construction of the works, with a complex procedure within the construction contract for monitoring the creation of value against the provision of funding by investors and lenders.

plan is to ensure firmly committed availability of all finance needed for completion of the project prior to the start of main construction. This eliminates any conceivable possibility of cancellation due to lack of funds. Although main construction is not scheduled to commence until the latter part of the second quarter of 1987, commitments are already in place for substantially all of the monies needed. Understandably, the principal caveat to such commitment at this stage is continued economic viability of the project in the light of concession terms finally issued by the U.K. and French governments. Based on a seven-year design and construction programme, with an average inflation rate of 7% and an average interest rate of 11%, the total cost estimate and related funding requirement are as shown in Table 5.

Funding Requirements Financing and Cost (see Fig. 14) The principal intent of the financing

Funding requirements for the Tunnel project are given below:

2 8 0 TUNNELLING AND UNDERGROUND SPACE TECHNOLOGY

£ Million Equity raised from U.K., French and worldwide markets Main bank loan Stand-by bank loan

Total funds committed for completion of the project

1000 4000 1000

6000

NB: On current forecasts, the main bank loan will only be drawn to the extent of £3696 million.

Equity U.K. and French owning companies will be set up as single-purpose organisations so that all surpluses after deduction of operating and financing costs will be available for distribution to shareholders.

Volume 1, Number 3/4, 1986

Table 5. Total cost estimate and construction cost breakdownfor the Channel Tunnel project.

Table 6. Three phases in which equity moniesfor the Channel Tunnel project will be raised.

£ Million 236 684 284

Construction cost b r e a k d o w n

British terminal and surface works British tunnels British fixed equipment French terminal and surface works French tunnels French fixed equipment

153 486 261

Rolling stock and locomotives

227

Total at 1985 prices Total at current prices

£ Million

Equity 1: Provided by current shareholders of Channel Tunnel Group and France Manche in accordance with commitments already held.

2331 2725

Owners costs during construction period. Allowance for inflation during construction period. Allowance for capitalised interest during construction period. Sub-total of cost estimate Overall financing contingency, additional to normal contingencies provided within design and construction price.

368 586 1057 4736

Equity 2: To be raised in October 1986 by a widespread international private placement.

200

Equity 3: To be raised internationally, including by public subscription in the U.K. and France, immediately after the Ratification of the Treaty and prior to the commencement of main construction work. Initial issue date is to be during the third quarter of 1987, with the balance being called, probably in two tranches, during the eady years of construction.

750

1000

Total cost estimate

50

Total of equity monies to be raised In cash

5736

1000

ChannelTunnel master progrommebarchor~c 1986

1988

1987

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1993

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Volume l, N u m b e r 3/4, 1986

TUNNELLING AND UNDERGROUNDSPACE TECHNOLOGY 281

Equity monies will be raised in three phases, described in Table 6.

Finance How is it raised?

How much is needed?

Loan Monies (see Fig. 15) r-

~m

[m

Contingency

IOOO

1057

Capitalised interest

586

InfLation

368

Owners cost

2725

Capitol cost

IO00

Standby bank Loans

3696

Bank Loans

Interest received on cash

40

Equity

I000

£5736 m Total

£5756 m Total

Figure 14. Financingfor the Channel Tunnel project.

4700 °°°° L 5000

r I : Standby credit for I I contingency I I I_1 I Unutitised Loon facility

:/

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o1:::7 1986 Key events

1988

Equity Equity I 2 3 loans Commitments

1990

1994 1996 Z~ A Dividends Opening start

1992

1998 2 Z~ Debt repaid with retinoncit~

Z~ Debt repaid without refinancirR

Both the main and stand-by bank loans, totalling £5000 million, are already fully underwritten in principle and will be syndicated on the international markets during the latter part of 1986. The loan agreement will be signed immediately prior to ratification of the treaty so that monies are available for drawdown after Equity 3 has been successfully issued. The bank facility so created may then either be drawn directly in different currencies or used to support alternative methods of funding if these are less costly. Once the T u n n e l is in full operation, it is intended that the bank debt will be progressively refinanced by the issue of long-term bonds repayable out of future cash flow. Such refinancing is entirely normal for a project of this kind and will serve to lengthen the maturity of debt, thereby freeing additional funds for distribution to equity shareholders. Any part of the bank debt not refinanced will be repaid out of a dedicated percentage of T u n n e l revenues. As a consequence, it is estimated that all bank debt will be refinanced or repaid within a period of 15 years from the date on which it was incurred. Conclusion

All of us who have been involved in the development of this project and the frenetic preparations which preceded the submission of our proposal, are excited at the prospect which now lies before use, and are very conscious of the scale of our task. We know that tunnellers worldwide will be watching our progress, as they have done in recent years for the Seikan Tunnel, aDd we shall no doubt be able to rely upon their collective experience when we are in need of advice. []

Figure 15. Equity and debt repayment plans for the project.

282 TUNNELLINGAND UNDERGROUNDSPACE TECHNOLOGY

Volume 1, N u m b e r 3/4, 1986