This Compilation of TAC Papers was prepared courtesy of

Green Heart Tunnel, an environmental solution for the Dutch High Speed Line

Ir. Hans Burger Sr. Advisor DHV B.V.

Tunnel Engineering Consultants (TEC), the Netherlands

TEC is a permanent Joint Venture between Royal Haskoning, DHV and Witteveen+Bos

Abstract:

The green Heart Tunnel is a shield driven tunnel of 8 km length in the Dutch part of the High

Speed Line South from Amsterdam to Paris. The tunnel consists of a mono-tube with an internal

diameter of 13,30m, which is divided by a wall in the middle in two tubes. The TBM used for this

tunnel has a diameter of 14,85m, which is still one of the biggest soft soil TBM’s of the World.

Important keywords in the High Speed Line Transport are: Fast, Comfortable and Safe. Another

important objective was: it had to be properly assimilated into the urban and rural landscape

environment and the environmental impact had to be minimized. In this aspect the thorniest

problems during decision making process was the question: Should the High-Speed Line cross

through the Green Heart of Holland, or shouldn’t it. Finally the Parliament approved a route that

would run through the Green Heart. The most important feature of this route is the eight

kilometers long shield driven tunnel, which will conserve this unique Dutch landscape. The

tunnel is realized in such a way that both damage to the landscape and disruption to local

residents due is minimized. The construction started in 2000 and was finished in 2005. The

presentation will describe the Unique Green Heart area, the most important design and

construction items and the basic safety concept for such a long tunnel. It will show a lot of

pictures and animations of the construction principles and the TBM operation.

Keywords: Holland; shield driven tunnel; environmentally friendly; high speed rail link; reduced

energy consumption; European; Holocene Westland geological formation; Twente Formation;

Urk Formation; tunnel boring machine.

Burger, H.Sr. Green Heart Tunnel, an environmental solution for the Dutch High Speed Line. 2008 Tunnelling Association of Canada Proceedings.

1

Green Heart Tunnel An Environmental solution for the Dutch High Speed Line Ir. Hans Burger Sr. Advisor DHV B.V.

Tunnel Engineering Consultants (TEC), the Netherlands

TEC is a permanent Joint Venture between Royal Haskoning, DHV and Witteveen+Bos

ABSTRACT

A beautiful piece of countryside, located in the western part of the Netherlands, is surrounded by

the dense urban areas of four cities: Amsterdam, Rotterdam, Utrecht and The Hague. Because of

its location and its rural beauty, this central landscape within the urban agglomeration of Western

Holland is referred to as Holland’s “Groene Hart” (Green Heart). About 600.000 people live in this

area. Most of the land is countryside, mainly used for agriculture purposes, such as dairy farms

and market gardening. The Green Heart is one of last remaining undisturbed natural landscapes

in Western Holland. Fragmentation of this region will increase urban development and decrease

the value of the scenic countryside. Considering these factors, the Dutch Government decided in

1998 that the straightest possible and acceptable route between Amsterdam and Rotterdam

would be an eight kilometers long shield driven tunnel under the Green Heart to minimize

nuisance and disturbance during the construction, as well as during future operation.

The paper will describe the unique scene of the Green Heart area, the most important design and

construction items to reduce the environmental impact on this area and the basic safety concept

of such a long tunnel.

1. INTRODUCTION

From this year the Netherlands are connected to the European network of high speed lines. It is

now waiting for the rolling stock providers to start operation after delivering trains with the newest

ERTMS (European Rail Traffic Management System) and after finishing the try-out operations.

2

The new High Speed Rail Link offers an

efficient and environmentally friendly

alternative to transport by air or road. More

intensive use of rail at the expense of road

and air transport will mean less air pollution,

reduced energy consumption and fewer

potential fatalities and injuries. There will be

no motorway tailbacks or waiting at the check-

in desk at Schiphol Airport. Instead, travelers

will enjoy smooth journeys at up to 300 km an

hour, not only between the European

countries but also inside the Netherlands itself.

Traveling from Amsterdam to Paris will be just

a matter of three hours in armchair comfort,

and the journey from central Rotterdam to the

centre of London will take three hours through

the Channel Tunnel Rail Link.

The section of the HSL between Amsterdam and the Belgium border consists of approximately

100 kilometers of new track, which is suitable for speeds of up to 300km/hour.

In order to ensure that the HSL would be properly incorporated into the urban and rural landscape

environment, the line includes more than 170 bridges, tunnels and underpasses. Much attention

was also paid to the architecture of the required infrastructure engineering.

2. FROM ROUTE DECISSION TO CONTRACTING

Since 1991, the High-Speed Line has gone through all the statutory procedures for major

infrastructure projects according the Dutch Infrastructure (Planning Procedures) Act. Following

the approval of the High-Speed Line KPD by the Parliament, at the end of April 1997, detailed

design of the route began. This was done in close consultation with local residents and the

relevant local, provincial and national authorities and governmental agencies.

In this aspect one of thorniest problems during the decision making process was the question:

Should the High-Speed Line cross through the Green Heart of Holland, or shouldn’t it? There was

an alternative route following the Highway A4 Amsterdam-The Hague and the Highway A13 The

Hague-Rotterdam. This alternative route alongside the highways should cause a lot of problems

as well in existing urban areas as in new to develop urban areas. Also this alternative route

alongside the Highways should cost about 500 million Euros more than the former plan through a

part of the Green Heart. Finally the Parliament approved a route that would run partly through the

Green Heart, provided that the impact on the surrounding countryside is minimized and the extra

costs of the environment friendly solution will not exceed 400 million Euros. The most important

feature of this route is an eight kilometers long shield driven tunnel, which will conserve a large

part of the unique Dutch landscape “The Green Heart”. This tunnel meant that relative little

excavation work was necessary in this area and therefore both damage to the landscape and

disruption to local residents due to construction work would be minimized.

The Design and Construct contract procedure for the shield-driven Green Heart Tunnel, which

started in September 1998, was an original and unusual way of tendering. There was no

traditional advertisements providing information, process to records and general specifications,

but, instead, an informal frank and public approach through an organized symposium with

domestic and foreign contractors. The main goal of this symposium was to issue a “call to the

market” for an intelligent, creative and original solution for the shield-driven tunnel project, which

is one of the biggest and most expensive structures of the High-Speed Line Rail Link.

3

3. PROJECT ORGANIZATION

The High-Speed Line Project Organization was responsible for the construction of 100 km of

high-speed line. Within the Organization ProRail (Dutch Railways Infrastructure Management),

Movares and DHV B.V. worked together under responsibility of the Ministry of Transport, Public

Works and Water management and the Ministry of Housing, Regional Development. In 1998 the

structure of this organization changed from a preparatory phase structure to a structure

emphasizing project construction. The total line was divided over five Project Offices with a

central steering board.

The Green Heart Project Office within the Project Organization High-Speed Line-South had the

following tasks:

• To realize the tunnel design and construction within the budget limit as stated by the

parliament;

• To establish the necessary conditions for realization of ground purchases, relocation of

cables and ducts, formal permissions, etc.;

• To communicate with local residents and authorities concerning the tunnel design and

construction and the environmental impact and the total safety concept of the a train with

300 km/hr in a 8 km long tunnel;

4. REFERENCE TUNNEL DESIGN

The purposes of preparing a reference tunnel design were:

•••• To formalize the Key Planning Decision as part of the Dutch Infrastructure Act;

•••• To establish a basement and conditions for necessary administrative consultations

with the local residents and authorities;

•••• To minimize design efforts (for the Design and Construct contract) of candidate

contractors;

•••• To provide a guide in design, together with a quality standard as envisioned by the

client

In the reference design the start shaft is located in the north near to the Highway A4 and a small

river. The end shaft at the south is near the Hazerswoude village. Two shield-driven tubes of 9.54

m inner diameter should connect start and end shafts. The distance between cross-passages

between the tubes is about 300m and an emergency and maintenance shaft is projected every

2 km. It was assumed that freezing and grouting techniques should be used to construct the

cross-passages. Both tunnel tubes would be built using two shield-driven machines along 7 km

4

length. The distance between the tunnel axes were projected from half the diameter at the

location of the shafts, till one diameter for the rest of the tunnel alignment.

Because of the speed of 300 km/hr of the trains the vertical curves are between 20,000 m and

50,000m, and the horizontal curves are more than

4,250 m. The maximum inclination is less than 2.5%.

The total free tunnel cross-section was projected to be

a minimum of 60 m2, to fulfill the requirements of

comfort in the trains due to air pressure differences

that occur when a train drives into the tunnel at high

speed. Additional measures to prevent passengers

from feeling air pressure differences in their ears are

adjustment of several vertical airshafts to the surface

along the alignment of the tunnel.

5. GEOLOGICAL PROFILE OF THE TUNNEL SITE

The soil characteristics of the Green Heart are very challenging. There are multiple soil layers

consisting of salty and brackish water, with a fresh water table up to the ground surface. The

Holocene Westland geological formation, with 10 to 15m thick peat (specific weight of 1100-1300

kg/m3) and marine clay layers settled on loose sand, gives a proper picture of the difficult soil

conditions for any construction works.

Under this Westland formation is the Twente and Urk formation reaching till 25-30m under the

surface. This formation consists of fine sand layers with a density between 10% and 60%. This

means there is a great risk of squeezing, settlements and possibly liquefaction.

Any construction works planned to realize with these soil conditions should be carefully

considered, taking in account the influence of soil disturbance on the structures or shield-diving

process.

6. ADDITIONAL REQUIREMENTS BECAUSE OF ENVIRONMENTAL REASONS

Since the decision for a tunnel under the Green Heart was made for reasons of environmental

protection, these considerations play an important role in the project design of the tunnel. To fulfill

these requirements, especially all the logistic works for the shield-driving process like production

and transport of concrete elements, bentonite-soil separation factory, etc., it was concluded that

the driving of the tunnel with a TBM was only allowed to start from North shaft. This scheme will

entail serious restrictions on the site space and construction activities.

The critical environment was a main reason for establishing the Board Commission for

Construction Activities, composed of representatives of local residents and authorities, together

with representatives from the Project Office Green Heart Tunnel.

5

Conclusions from the frequent meetings of this group resulted in additional requirements or

challenging incentives to reduce construction hindrance or to minimize the environmental impact,

specified in “Terms of Reference” and communicated to the candidate contractors.

Examples of these wishes and/or requirements are:

• Realize TBM section as long as possible (in stead of longer cut and cover ramps)

• Minimize the dimensions of the construction sites

• Minimize the soil waist of out coming soils (thus maximize soil recycle possibilities)

• Minimize the transport of materials by trucks

• Minimize or avoid the construction nuisance at critical sites (minimize sheet pile driving

for retaining walls; limiting of working hours between 7.00h and 19.00h)

• Minimize the dimensions of definitive constructions at the surface, like ramps and

accesses to shafts

All these additional requirements and wishes were taken into account in the tender of the Green

Heart Tunnel to select the contractor with the most attractive bid.

Beside these environmental criteria there were also the following economical criteria:

• Total construction time (as short as possible)

• Project risk profile ( as low as possible)

• Quality assurance

• Innovation aspects

• Expected maintenance

• Price (of course)

The effects of all these items were translated into money. This was incorporated in a scheme to

evaluate all these effects in the bid of the pre-selected five contractors. The scheme was

developed with the reference design as starting point. For each issue a maximum amount was

set and a parameter chosen. The reference design solution was zero. Solutions better than the

reference design meant a bonus and solutions inferior to the reference design meant a minus.

The sum of total bonus and minus was adapted in the bid as an apparent decrease or increase of

the bid. The Total amount of bonuses could reach 55 million Euros on an estimated total

construction cost of 430 million Euros.

Of course this bid evaluation procedure had to be completely transparent and known to all

bidders in advance and in accordance with EU ruling. The thought behind this approach is that

bidders can focus in their design on all those items that will give the most advantage in achieving

the order. For the Client this approach had the advantage that there was a real challenge for all

the bidders to optimize their design at those aspects. The whole tender procedure including the

design period for the contractors took about one year. During this tender there was a technical

dialogue between client and bidders to exchange ideas of alternatives and to verify if they meet

the requirements. The aspired innovation asked for a very “open” communication with the

individual bidder about his developments in the design and a positive attitude concerning

demands for changes in the Technical Requirements. The Bidders had to be assured that their

demands for changes in the Technical Requirements were treated confidentially because they

could easily be linked to their proposals.

6

7. ALTERNATIVE DESIGNS AND THE WINNING CONCEPT

Besides the concept of the reference design there were two other possible concepts:

• The double-O-tube, only practiced in Japan

• The mono-tube with two tracks, separated by wall in the middle

The Dutch safety concept for High-Speed trains requires separated tubes for each track with connections on regular distances between these tubes. In both above mentioned concepts these connections are easily to realize by rather simple doors in the separation walls. This in contrary to the reference design, where it is necessary to dig a cross-passage between both shield-driven tubes. Another advantage of both mentioned concepts is the smaller cross-section space which is needed and the less soil excavations.

Disadvantages were the technical feasibility of these concepts in terms of experience and

manufacturing of TBM’s with this kind of dimensions.

In the Design and Construct tender procedure five international combinations of contractors were pre-selected. Four of them did a bid according an optimized reference design. One of them considered also the double-O-tube concept and another the mono-tube, but both choose at the end still for the reference design concept with some optimizations.

7

The winning concept of this Design and Construct tender was a French/Dutch combination,

Bouygues/Koop, with their design of a mono-tube tunnel: a huge shield driven tunnel with an

internal diameter of 13.30m, which is divided by an internal wall in two tubes. To construct this

mono-tube tunnel a TBM is used with a diameter of 14.87m, which was till two years ago the

biggest soft soil TBM of the world. The shield-driven section runs at an average depth of 30m

below surface level over a length of 7,160 m. Here the tunnel is enclosed by the aquifreous sand

deposit, which is very appropriate for the bentonite shield-driving process. The ground water

flows are barely disturbed, because they have sufficient space to pass below and above the

shield-driven tunnel. Due to the depth, the TBM has sufficient soil and weight above it to prevent

flotation caused by the ground water. This is in contrary with beginning and end of the shield-

driven section where the TBM is passing through clay and peat layers with very small cover.

Without precautions here should occur real blow-out problems. Especially at the north side,

where also a small river is passed by the cover is too small. The original soil is removed here and

replaced by, sand with an over-height and in the river part by sand-cement mixture. At the south

end a 500m long temporarily embankment of sand is used on top of the surface above the tunnel

alignment. With both solutions the wish of a longer shield-driven section with shorter cut and

cover ramps, was fulfilled. The risk profile of this construction method was smaller and especially

the impact on the environment was reduced.

The last parts of the ramps of the tunnel are constructed as cut and cover works. At the north side

the first 540m of this access ramp is in open trough, the last 120m is closed. At the south side the

access ramp has a closed part of 420m and a connecting open access ramp of 350m.

Seven shafts for maintenance, air pressure discharge, and technical installation are embodied in

the tunnel. The shield-driven section of the tunnel has three combination air and access shafts,

which were also used during the shield-driving process for inspection and repair of the TBM.

Additional two smaller air shafts are located 500m after both entrances, which are used

exclusively as air pressure reduction shafts. Both the northern as well as the southern access

have again a combination air and access shaft in the closed section, positioned at the there

located service buildings. The roofs of these tunnel access ramps have additional been provided

with holes in order to create as gradual a transition as possible from the open air to the closed

tunnel.

Because the goal of the Green Hart Tunnel was to reduce the environmental impact as much as

possible special attention was given to

minimize the dimensions of all the structures

above surface, like the air and entrance shafts

buildings as well as the service buildings near

the tunnel accesses. This was realized by

locating most functions beneath surface level

and to give special attention to the architecture

in order to fit in these structures in the

surrounding landscape. A special function

related to the environment was the sound

damping boxes which were designed

underground of each air shaft.

8

8. DESIGN, CONSTRUCTION AND ENVIRONMENT

The design and construction of the mono-tube concept was totally the responsibility of the

French/Dutch combination, Bouygues/Koop. It was especially the international experience of

Bouygues that made it possible to design and construct such a huge shield-driven tunnel. The

design of the cut and cover parts in the typical Dutch soft soil is engineered by TEC in

subcontracting of Bougues/Koop.

8.1 The TBM

The four main sections of the Tunnel Boring

Machine together, form a traveling factory of

120 m long and weighing more than 3,300

tons and a diameter of 14.87m. The shield

of the TBM consists of a drill wheel (1,932

tons), the first follow-on platform (758 tons),

the bridge (217 tons) and the second follow-

on platform (439 tons). A TBM of this

magnitude had never been used before

anywhere else in the world.

The boring process took place from the

construction site at the north next to the

highway A4 and the Does River. That is the

site where the starting shaft and the

construction pits for the open and closed access ramps are situated. This is also the place where

the logistic centre of the shield-driving process is situated, like the storage place for tunnel lining

elements, the portal crane for lowering heavy loads down in the shaft and the soil/bentonite

separation plant, as well as the temporarily soil storage basins. Since the decision for a tunnel

under the Green Heart was made for reasons of environmental protection, this was the only

acceptable place to start the driving of the tunnel with a TBM with good accessibility for large

construction materials by trucks.

In 2001, the TBM has been assembled in sections in the starting shaft (30m wide and 80m long).

The TBM was built at NFM in France and transported in sections to Netherlands by sea ship. In

the Netherlands the further transport was carried out by flat barges over shallow Dutch waters.

The last km’s the transport of the sections took place from a jetty on multi wheel trucks to the site,

where the sections were lowered by the portal crane in the start shaft.

9

8.2 The drilling process and construction of tunnel lining

Behind the 12m long drill head is an erector situated. This places the pre-fabricated concrete

tunnel elements (14.5 tons each) into position within the shield of the machine. Together, ten

segments form a closed circle lining of 0.60m thick. Every hour a tunnel lining of two meters

length is completed. The drilling wheel at the front of the boring shield scrapes the sand loose.

The sand is mixed with bentonite, a natural type of clay, which is continually pumped to the front

of the drilling wheel. The bentonite has two functions. At first the hydraulic pressure of the

bentonite supports the drill front of sand by forming a membrane of bentonite cake. Secondly the

mixture of sand and bentonite is transported by a system of ever lengthening piping to the

separation plant on the northern construction site.

The bentonite is separated from the sand in this huge filter system of the separation plant and

pumped back to the TBM. The residual clean sand – a total of about 1,350,000 cubic meters – is

reused for other construction projects as much as possible. Because of this recycling of sand as

construction material the requirements to the separation plant were severe.

The average daily speed of the TBM was 9-12m. The maximum daily speed was almost 30m.

8.3 The finishing work of the inner tunnel furnish

Behind the drilling shield and erector moves the first follow-on platform, containing the operator’s

cabin, the pumps and other apparatus required. The second follow-on platform is sixty meters

behind the first one. Both platforms are connected through a bridge construction underneath

which the tunnel elements and the elements of the technical tunnel gallery are transported.

This tunnel gallery (2 m height and 2.5m wide) is situated under the future tracks. Besides the

gallery stabilized sand (sand/cement mixture) is deposited to give the tunnel weight, to prevent

flotation caused by the ground water. The second follow-on platform drives on the stabilized sand

fill.

After the second follow-on platform has passed a concrete floor slab is constructed across the technical gallery and the stabilized sand fill. A sliding formwork for the partition wall follows at about 600 m behind the second follow on platform. In this formwork the partition wall of 45 cm thick is cast across a length of 12 m.

Next in each tube two concrete platforms

at both sides are constructed. The

platforms along the partition wall have the

function of evacuation path in case of

emergency. The platform at the outer side

has the function of inspection path. Both

the free spaces under the platforms have

a function as cable duct.

8.4 continual, industrial and logistical optimized construction process

The TBM with follow-on platforms and finishing work was a continual process that operated daily

24 hours, seven days a week, during a period of approximately 3 years. Supply and discharge of

materials, equipment and personnel took place through the tunnel sections that already have

been built. To make these possible special trucks were designed for this purpose. These trucks

had operating cabins at the front and back sides, which was required because the trucks could

not turn around inside the tunnel. Strict procedures and traffic rules concerning safety and

progress supervised this continual logistical process of very high level.

10

The three air and escape shafts in the shield-driven section to the surface had also an important

maintenance function during the drilling process. The TBM drilled through these circle shaped

shafts, which were constructed as slurry walls and filled up with low-strength concrete. Inside the

shaft the TBM remained some days to undertake any necessary maintenance or to replace the

teeth of the drilling wheel if they were worn or damaged.

9. SAFETY CONCEPT IN THE GREEN HEART TUNNEL

The most important safety measure is already incorporated in the basic design concept of the

tunnel: two separated tubes for each track, provided with safe escape routes for the passengers

to reach in short time a safe haven. Important in respect to this escape route is that passengers

have to evacuate on their own, without necessarily, the help of rescue-workers. This so called:

self evacuation is essential in minimizing the amount of casualties.

That is why in the mono-tube a partition wall is incorporated, provided with adjoining platforms

over the whole length of the tunnel. The height of the platforms is about 0.35 till 0.55m above

railhead and with a width of about 1.45m. This platform directly at the inside along the partition

wall between both tracks provides an acceptable and fast dis-embarkation even in emergency

circumstances. Also at the outside of the tracks are 0.80m wide platforms, which are not intended

as escape route, but may be seen as additional if the situation requires. The main escape route is

lit up during an emergency,

equipped with pictograms

showing the shortest way to an

emergency door to the safe

location in the other tube. The

distance between these doors is

at most 144m and therefore the

longest distance to the safe

location 72m. This is an important

advantage of this mono-tube

concept in comparison with the

reference design (cross

connections every 300m). Other

safety provisions are a handrail

along the wall, a rough surface of

the platform, no obstacles and staircases in this escape route to the save location. The escape

doors to the other tube are sliding doors and are 2.40m wide.

In case of emergency, when passengers evacuate to the other safe tube, they can wait there for

assistance or leave the tunnel via the emergency shafts, which are situated every two kilometers.

The safe haven, which is the not-incident tube, will be safe against smoke and fire for at least 4

hours. Emergency services can use the tunnel entrances and the escape shafts for the supply

and removal of equipment and possible victims. There are lifts for the emergency services inside

the shafts. Evacuees have to use the staircases in the shafts.

In case of emergency the ventilation system is automatically started and geared towards the

driving direction of the train. This implies that there is no smoke behind the train and the fire

brigade can approach the train safely from there.

11

10. CONCLUSION

The High Speed Line is a unique project, interplay of state and private enterprises, resulting in a

safe and fast transport system that meets both the needs of our times and the needs of tomorrow

and beyond. It has been realized with respect to the environment and the remaining traditional

Dutch landscapes. The shield-driven tunnel under Holland’s “Green Heart” was constructed as an

environmental friendly solution to realize the High-Speed Line-South, to meet future needs of

development and mobility.

The parliament considered the Green Heart Tunnel as a sustainable solution, which justified the

extra cost of this tunnel of about 400 million Euros. The dimensions of this shield-driven tunnel

were so extra ordinarily, that considerable research and development was performed and new

experience was gained. These results have been of use and will be available for use on other

underground projects.

The whole High-Speed Line south is now finished and in short time the High-Speed Trains will

transport passengers fast, comfortable and safe everywhere to other Capitals in Europe. This will

add an environmental friendly opportunity in comparison to traveling by car and plane.

.