Why an immersed tunnel?

Clearing the way
for the new waterfront
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The Sørenga construction site. The main south
going artery out of Oslo (Mosseveien) is temporarily
moved to quay areas to allow tunnel construction
work to be carried out.
The Norwegian Public Roads
currently acts as a barrier that
to public and residential/commercial
Administration (NPRA) is building the
separates the harbour areas from the
development for Oslo’s population,
Bjørvika tunnel in the centre of Oslo.
city. The new tunnel will accommodate
and visitors.
This will remove substantial traffic
a traffic volume of 100,000 vehicles a
volumes from a large area along the
day underground. This will release the
The Bjørvika road construction plan
fjord water front. The E18 motorway
quays and previously trafficked areas
has two stages. The first stage is the
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The first tunnel element was
towed into the Oslo fjord on
13 August 2006.
construction of the tunnel. The second
can then be started. This work will
and people will be able to walk and
stage starts after the E18 motorway
continue until 2012.
cycle from the inner city to the fjord.
has been realigned through the new
The Oslo Port Authority and the
tunnel, thus releasing the area to new
The benefits to the city will be cleaner
NPRA have taken responsibility for a
uses. The construction of the most
air and less noise. Large areas will
comprehensive clean up of pollution
important streets in the new city zone
be released for city development
of the seabed and of the piers.
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Why an immersed tunnel?
The seabed of the inner Oslo fjord mainly
consists of clay and in some places bedrock
is as deep as 50 meters below the top of
the clay layer. This means that if a sub-sea
rock tunnel were the adopted solution it
would, even with very steep gradients,
be several kilometres long. NPRA has
therefore chosen to build an immersed
tunnel. This type of tunnel is constructed
by building in elements on land that are
subsequently floated into position and
lowered onto the seabed. It is the first time
that the technique has been used for a
tunnel with passenger traffic in Norway.
The immersed tunnel is made up of six
elements. Each element is 112.5 meters
long, 28–43 meters wide and 10 meters
high. The tunnel roof will lie eight to eleven
meters below the average water level.
The immersed tunnel will consist of two
tubes, with three lanes in each direction
and sufficient height inside the tunnel
for signs, fans, surveillance systems and
lighting. The immersed tunnel is being
built at Hanøytangen dry dock in Askøy
municipality outside Bergen. Construction
started in 2005 and will end in 2008. The
elements are being built two at a time
in the dock. The two first elements were
towed to Oslo in August 2006. The last
two will be delivered in the spring of 2008.
The journey from Hanøytangen to inner
Oslo fjord takes around five days. The
dock is filled with water, the elements are
floated out and are towed along the coast.
The open sea sections expose the tunnel
elements to the highest loads they will
experience in their lifetimes. Prestressing
steel tendons are stretched through ducts
in the roof and bottom plate to reinforce
the elements during the tow. Where wave
heights of more than 5 meters are forecast,
the convoy will find harbour shelter. The
tunnel has sufficient strength and built-in
flexibility which enables it to withstand
earthquakes. All six elements will be
anchored alongside the Bjørvika quay-side
by the spring of 2008. The submersion
and installation work can then begin. This
will take around two weeks per element.
The element is equipped with an access
tower and a land surveying tower. Marine
based operations will be carried out using
special equipment from a Dutch operator.
A vessel will lay a gravel foundation
on the excavated fjord bottom with an
accuracy better than +/- 3 centimetres.
The immersed tunnel lies on the gravel
foundation without any other form of
foundation being required. The tunnel
elements have an unladen weight of 1.1
which means the load exerted on the
fjord bottom is marginal.
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Diaphragm walls
The concrete tunnel on the quayside at
Sørenga is being built using the diaphragm
wall technique. A 1 meter wide trench is
excavated down to a depth of 25 meters
and is filled with support fluid to prevent
collapse. Reinforcement baskets are
lowered into the trench which is then filled
with concrete from the bottom up. The
support fluid is pumped out and is reused.
Diaphragm walls act as an outer support
for the excavated construction area. Each
diaphragm is six meters long. After the
walls have been cast, sufficient clay is
excavated to allow the tunnel roof to be
cast. The roof then braces the walls while
the loose material between the roof and
floor is excavated. Finally the bottom plate
and walls are cast.
Immersed
tunnels worldwide
Links east to west
The Michigan Central railroad tunnel
opened in July 1910 and was the world’s
first immersed tunnel for passenger
transport. Busan Geoje in South Korea
will be when completed the world’s
second longest (3.2 km) and the world’s
deepest immersed tunnel at 50 meters
below sea level. Construction started in
2004 and the tunnel should be completed
in 2007. A 1.4 km long immersed tunnel
is also under constructed in the Strait of
Bosporus at 61 meters below the water
surface.
Bjørvika tunnel links Festning tunnel in
the west with Ekeberg tunnel in the east.
When completed, the tunnel will have an
unbroken length of six kilometres from
Framnes (Kiel ferry terminal) to Ryen.
Complex work from the quay side and
into the existing tunnels is currently being
carried out at both ends of the project.
An underground road intersection is being
built in the rock at Ekeberg with exits and
slip roads in both directions.
The section of the Festning tunnel adjacent
to the new Bjørvika tunnel must be lowered so that the road level can be aligned
with the immersed tunnel road level. A 100
meter long ‘basement’ is therefore being
excavated under the existing tunnel. ‘The
basement’ is three meters high and a new
floor is being cast with a profile that will
meet the immersed tunnel road. Moving
the traffic down one floor will be a critical
phase of the project.
There are 108 immersed tunnels for
passenger transport around the world.
Japan has 20 and there are 48 in Europe.
The most famous immersed tunnel
project in Scandinavia is the Øresund
link between Malmö and Copenhagen.
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Low heat concrete
The concrete used for immersed tunnels
has been extensively tested. Low heat
concrete design mix is used in very thick
constructions to reduce the likelihood of
cracking and to give a more dense and
water tight construction. Ingress of road
salt and salt water, which can generate
corrosion, is also concrete. 50 per cent of
the cement in low heat cement is replaced
with fly ash, which is a coal fired power
station by-product. Silica fume, which is
a common binder additive, is also used.
Low heat concrete hardens more slowly
than standard concrete and shuttering
must therefore stand a bit longer than for
normal concrete.
Casting at Hanøytangen dry
dock outside of Bergen.
Each of the six elements is
as long as the Plaza hotel
(central Oslo) is high.
Immersed tunnel facts:
Length: 675 meters
Width: 28– 43 meters
Weight: 30 000–37 000 tons per element
meter
Concrete consumption: 90 000 m³
Thickness of walls, roof, floor: from 1–1.4 meters
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Safe tunnel
Tunnels will be equipped with the
latest surveillance and safety systems
to ensure the road network is as safe
as possible. Cameras with incident
detection systems will be monitored
from the Traffic Control Centre in Oslo.
The Traffic Control Centre can remotely
control lane signals and barriers and so
close lanes and redirect traffic when maintenance is being carried out or in the event
of an accident. The Norwegian Public Roads
Administration has tested different types of
fire insulation for the Bjørvika tunnel. A fire
retarding material will be fitted to the inside
of concrete elements to ensure that the immersed tunnel can withstand extreme heat.
The tests were carried out by SP Swedish
National Testing and Research Institute in
Borås, Sweden. The materials were tested
against the RWS curve. This means that the
materials were exposed to a temperature
increase from 0 to 1,100 degrees Celsius in
the first five minutes of the test, and then
to 1,350 degrees for two hours.
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Urban development and
environmentally friendly transport
Project main goals
Urban development and environmentally friendly transport are the two main reasons
behind the implementation of the Bjørvika project. The tunnel will result in 7 of 10
vehicles in the Bjørvika area being transferred to an underground route.
We therefore achieve:
• Less dust
Reduced dispersion of particles and exhaust gases and therefore better air quality.
• Less noise
Traffic noise reduced by 50 percent.
• Cleaner port
The Norwegian Public Roads Administration is removing large amounts of polluted
ground and contaminated sediments from the seabed of the fjord. Clean clay
excavated from the immersed tunnel trench will be used to cover heavily polluted
areas in the harbour basin.
• Safer traffic
Accidents reduced by 50 per cent compared to existing surface roads of the same
standard.
The Bjørvika project in meters: 1 100 meters of tunnels, 675 meters of which is immersed • 8 000 meters of roads • 5 700 meters of
pedestrian and bicycle paths • 3 500 meters of public transport lanes
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Milestones
1983
Immersed tunnel included for the first
time in the ‘Fjordbyen’ study.
2002
A construction site in the middle
of the traffic
120,000 vehicles a day drive through
the construction area, including ferry
traffic and heavy goods vehicles
from the busy container port. All
temporary roads must therefore have
the same number of lanes during the
construction period as the existing
roads. Pedestrian and bicycle paths will
also be maintained at an acceptable
standard. New traffic patterns will
be introduced on several occasions,
so that contractors can gain access to
the site areas where the permanent
constructions are to be built. In the
spring of 2006, the south going artery
Mosseveien was moved closer to the
quay so that tunnel work could be
carried out. The south going railway
line ‘Østfoldbanen’, the railway line
to the port and the port access road
Havneveien will also be moved to
provide space for construction work.
Building roads to give buses
and trams faster routes
The Norwegian Public Roads
Administration on 23 September 2002
presented a development plan proposal
for a new E18 motorway route between
Festning tunnel and Ekeberg tunnel.
2003
The city council approves the road plan
on 18 June 2003.
2005
First construction contract signed on 30th
May 2005 with AF Spesialprosjekt for the
Sørenga contract. The contract for the
sea (“sjødel”) or immersed tunnel section
was signed with Arbeidsfellesskapet
Bjørvikatunnelen (Skanska with partners
Bam Civiel and Volker Stevin) on 11th
August 2005. The last main contract was
signed with NCC on 27th September
2005 for the Havnelager contract.
2005
The challenge for the Norwegian Public Roads Administration is to create a modern road
system which meets the cities and the new city area’s needs at the same time as providing
an efficient and safe road system for users. Public transport is therefore an important element in the new Bjørvika. Buses and trams will have a separate public transport lane in the
new main street and an extensive network of pedestrian and bicycles paths will be built.
Construction start on 15th August 2005.
Highway 4 ‘Nylandsveien’ has today an annual average traffic level of 40 000 vehicles a
day. The ‘Bispelokket’ interchange will be demolished and the elevated section of Nylandsveien will be lowered to ground level and become an important local street in Bjørvika.
A new bridge connecting the streets Bispegata and Schweigaards gate (adjacent to the
Middle Age Park) across the railway shunting yard area will also reduce congestion.
The two first elements towed to
Oslo. The Norwegian Public Roads
Administration has excavated 200,000
tons of polluted ground/contaminated
sediments.
2006
The two first immersed tunnel elements
completed at Hanøytangen in May 2006.
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Bjørvika, largest port clean up i
As of May 2006, the Norwegian Public
Roads Administration had excavated
and removed around 200 000 tons of
contaminated sediments from the Bjørvika
area. The sediments contain heavy metals,
oil and organic compounds. This is the
most extensive harbour clean up project
ever carried out in Norway. The polluted
materials are removed from the seabed of
the fjord, from piers and the land areas at
Sørenga and Havnelageret. This volume
contained 500 kg of heavy metals, which
have been removed and neutralized. These
are mainly PCB, lead, copper, chrome, nickel,
zinc, arsenic and organic components
such as oil and tars. The sediments are
transported to a land tip at Langøya and
to other approved tips.
A major problem experienced in the harbour
is that propeller wash from ships and
small boats every day churns up bottom
sediments and spreads particles containing
environmentally hazardous substances
through the water. The particles are
further transported by water currents.
Environmentally hazardous substances are
therefore easily available for absorption by
marine organisms. 43 000 tons of polluted
harbour sediment have been removed and
tipped at Malmøykalven deep sea fill. These
contained 177 kg of pure heavy metals.
Dredging through the Bjørvika pier. Oil
absorbent booms and curtains contain
the contaminated sediments.
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Health, Environment
and Safety
p in Norway
In 2006, 500 people were working
on the Bjørvika tunnel in Oslo and at
Hanøytangen outside Bergen. Around
10% of the workers are foreign
nationals coming from other countries
in the European Economic Area.
Environmental monitoring
The consultancy company Rambøll, on
behalf of the Norwegian Public Roads
Administration, regularly took samples
at up to 10 stations before construction
was started and continues their sampling
work while construction is in progress.
Some stations near construction activities
which are particularly critical to the
environment are monitored daily. The
Norwegian Public Roads Administration has
received permission from The Norwegian
Pollution Control Authority for dredging
and excavation work in the harbour and
on each land approach. Particle dispersion
limits have been set which are not to
The Norwegian Public Roads Administration has a full-time Health, Environment
and Safety coordinator (HES) for the
Bjørvika project. Contractors have HES
managers for their own contracts and their
own HES planning. A safe work analysis
is carried out for all operations where
there is a certain degree of risk. Safety
inspections are carried out each week, to
uncover conditons which could potentially
lead to accidents and injury. All employees
are encouraged to report undesirable
occurrences. Every third month, the NPRA
awards a prize for outstanding HES work.
be exceeded during dredging and this
is continuously followed up. Dredging
(underwater excavation) for the immersed
tunnel in Bjørvika affects water quality.
However, this is limited to a small area
surrounding the dredger. Measurements
taken by the company Rambøll show
normal particle consentrations in water
layers 50–100 meters from the dredger.
The churning of particles caused by
the dredger can be compared with the
churning which occurs when a ferry boat
departs. The dredging work is of limited
duration and does not lead to long term
deterioration of water quality.
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The city’s history
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Construction work takes place in an area
that can be considered to be the cradle
of Oslo. The work is therefore being
followed closely by archeologists from
the Norwegian Maritime Museum and The
Norwegian Institute for Cultural Heritage
Research. Archeological surveys were
carried out prior to the commencement
of construction. However, the Bjørvika
project provides a special challenge
because archeological finds can lie many
meters below ground level/fjord floor.
Archeologists therefore carefully follow
each bucket-load excavated along the
tunnel route. In the course of the first
year alone, archeologists have found
relics which provide good insight into
the use of the port across a period of
several hundred years.
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Bjørvika’s industrial history
– in brief
• Bjørvika tunnel is being built in an area
which has a 150 year long industrial
history. The river Aker, which runs out into
the Bjørvika bay, brought with it waste
and effluent from the saw mills, textile
factories, ironworks, mills and paper
factories that were located along the
river for many decades. Environmentally
hazardous substances have therefore been
washed straight out into the port basin.
The piers are built on frames of creosote
impregnated timber which were filled
with stone and city rubble. This today is a
pollution problem.
• The immersed tunnel route cuts right
through what once was the dry dock at
Nyland shipyard. There are therefore very
high levels of ground pollution here. The
coal and coke bunkers and oil tanks on
Paulsen quay have also left very clear traces
of this earlier use.
• Prior to 1976, a number of industrial
companies and households released
waste and sewage straight into the
river. For example, the nail manufacturer
Spigerverket in Nydalen released heavy
metals such as iron, copper and zinc
into the river Aker. Most of the factory’s
activities were shut down in 1989.
• Enormous amounts of sawdust have
been transported by the river Aker since
saw mill activities started in the 1500’s.
Hydrogen sulphide develops in the sawdust
in the anaerobic conditions. This is a volatile compound and the rotten egg smell
is easily detected when the sawdust is
excavated.
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Do you want to
visit us?
The Norwegian Public Roads Administration information centre is located in the
Bjørvika project office on quay called “Paulsenkaia”. The centre gives the public
an excellent opportunity to be informed about the urban development plan and
the tunnel and road project.
Everyone is welcome. We are happy to accommodate groups from high
schools, universities and interested clubs and associations, residents and
individuals. Opening hours are weekdays 12 pm – 3 pm. Groups can
however book other times.
Contact Ida Kojedahl on email:
idakoj@vegvesen.no
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Contact us!
The Norwegian Public Roads
Administration information centre
is located in the project office on
the quay “Paulsenkaia” in Bjørvika.
Reception
Vigdis Amsjø Berge
Tel: +47 24 05 87 30
vigdbe@vegvesen.no
Information consultant
Kjell Solem
Tel: +47 24 05 87 69 /+47 91 66 82 92
kjell.solem@vegvesen.no
Site Manager Sørenga
Oddmund Jessen
Tel: +47 24 05 87 33 /+47 91 83 15 73
oddmund.jessen@vegvesen.no
Oslo S
Site Manager Sjødelen
Geir Sorte
Tel: +47 24 05 87 51 /+47 91 75 40 63
geir.sorte@vegvesen.no
Site Manager Havnelageret
Kjetil Fløtre
Tel: +47 24 05 87 31 /+47 91 13 95 22
kjetil.flotre@vegvesen.no
Information
Centre
Opera
For more information:
You can obtain more information on the
E18 Bjørvika roject at this web address:
Produced October 2006
www.vegvesen.no/bjorvika
The aerial photographs in this brochure
were taken by Prosjektfoto AS. Other
pictures and illustrations: Karl-Fredrik
Keller, The Oslo City Museum, Bård
Gudim, Via Nova and Arild S. Solerød.
Design: Melkeveien designkontor
Printing: Rolf Ottesen AS
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