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A small good sets fire to in the medium of the underwater tunnel will recall us many memories... Ah, short-term profitability, what one would not make for it!!! Sieur Ponsolle was in a good place with the SNCF and in La Vie du Rail, it prefers the road solution, for a ex-railwayman, it is very intelligent...
You one will still need many innocent carbonized or gazed to put a little lead in the brain of these " brains "?
Eurotunnel proposes two solutions in drilled tunnel
Like held to recall it Patrick Ponsolle, president executive of
Eurotunnel, Wednesday January 5 2000, it is in accordance with
the obligations of the treaty of concession of 1986 (article 34.1)
that Eurotunnel has just given to the French States and British
a project of second fixed link under the Sleeve. Presented in
December, this project aims to supplement the existing tunnel,
«when the technical and economic conditions of realization
of such a connection allow it and when the increase in the traffic
justifies it without calling into question the awaited profitability
of the first work ».
Without anything to prejudge possible realization, Eurotunnel
thus entrusted to two consultants - French Scetauroute (Egis group)
and the Maunsell British - the realization of a feasibility study
of which we present the contents here. The treaty of concession
evoked only one road link, but it
was finally decided to also think of a
railway link. The exercise comprised a relatively flexible
schedule of conditions, the project especially having «to
answer criteria of safety at least as rigorous as those of the
existing tunnel », to be «complementary to current
operating system », and «to offer a capacity adapted
to the long-term forecasts of flow of the trans-manche traffic
».
Neither bridge, nor immersed work
If ten alternative projects of additional fixed
link were the subject of a feasibility study, only two solutions
in drilled tunnel were adopted.«The bridges and the immersed
structures, as in 1996, presented insurmountable difficulties,
while the recent technical developments as regards drilling make
it possible to plan to dig tunnels of large diameter »,
indicates one at Eurotunnel. Scetauroute and Maunsell thus proposed
a tunnel monotube 15 m in external diameter. A curious choice,
when it is known that the experts of the underground works recognize
as ideal the solutions bitube!
On the road assumption, the new
Channel tunnel is equipped with two flagstones of bearing forming
two levels reserved for the light vehicles, in a way identical
to the work currently in construction in Paris area, on western
A86. Here, each stage comprises two lanes and a hard shoulder.
As on western A86, the work accomodates neither heavy lorries
nor coaches. And, in this case, the existing tunnel under the
Sleeve is borrowed more only by the shuttles freight, Eurostar
and the goods trains, the coaches continuing to be transferred
onto shuttles with simple bridge.
On the railway assumption, the tunnel is equipped with a flagstone which receives
two separate ways of railroad one-way for Eurostar and the goods
trains.
In this case, the current tunnel is exclusively reserved for the
Eurotunnel shuttles transporting the cars and the trucks.
Tunneller with ground pressure and voussoirs prefabricated
The fire resistance , of course, was taken into account in calculations.
Thus, the structure even of the tunnel largely takes part in it,
by means of an exceptionally thick ring external (1 m) and flagstones
of reinforced concrete floor. «As a need, an additional
protection in the form of thermal plates would be added, specify
the consultants. The whole of the road version was calculated
on the basis of extreme assumption of fire during two hours, which
corresponds to the fire of a tanker of 50 m3 hydrocarbons reaching
1350°C»a data to be taken with much precaution, the
firemen being shown surprised by the violence of fire in the tunnel
of Mont.Blanc, March 24, 1999.
In the project, it is expected that each stage has of its own
distribution and its own sheath of extraction of the fume. In
addition, a play of communication would make it possible to regulate
the contribution of fresh air on each side of a fire starting
from the nonaffected stage. Lastly, as it has been just decided
for Mont Blanc, the tunnel would be equipped with two rescue stations,
located at two thirds of the course and accomodating permanently
of the personnel.
Same principles in the railway version which would be, it, equipped
with an automatic stopping device of the trains, side pavements
acting as device anti-derailment in addition.
Concerning underground work, the consultants estimate that they
can be carried out using a tunneller with ground pressure. «This
machine must make it possible to work either in closed mode, or
in opened mode, and seems adapted to the excavation of the grounds
met by the second fixed link », explain. The coating can
be ensured by precasted concrete voussoirs. As for the works of
accompaniment, they can, them, be embanked into traditional. Cast
iron voussoirs would be used with the right of these works.
Which cost?
Except cost of land acquisitions, the road project is evaluated
at 4,12 billion euros (27 billion francs), and the railway project
to 4,57 billion euros (30 billion francs). These figures advanced
by the consultants are regarded as «reasonable »by
Eurotunnel, which estimates that the control of the costs will
have to be guaranteed by a complete definition of the project
before publication of the invitations to tender, and by an extreme
rigour of these invitations to tender.
GUILLAUME DELACROIX Le Moniteur du BTP of 14-01-00