Civil Engineering Reference
In-Depth Information
days. In order to avoid that activities would lead to a delay in the boring pro-
cess at pressures of 4.2 to 7.5 bar, the divers remained under pressure for a
longer period of time - this meant weeks. In this period the divers breathed
a gas mixture which consisted of a mixture of oxygen (12%), nitrogen (45%)
and helium (43%). In order to keep them under pressure continuously, a
special accommodation with a pressure of 4 bar was built on the site; the
decompression from 7 to 4 bar, in respect of the decompression from 7 bar
to atmospheric circumstances takes up much less time. This accommoda-
tion consisted of 2 rooms connected to each other, one with a length of 4.7
metres and the other with a length of 7 metres and a diameter of almost two
and a half metres. The accommodation provided space for a maximum of
9 divers who could stay for a period of 4 weeks at most.
In order to travel to the excavation front, the divers stepped out of the habi-
tat into a connected pressure-shuttle which transported them by train to the
TBM. Having arrived, the shuttle connected onto one of the air locks which
provided access to the pressurized section of the boring machine. In the air
lock the divers were brought to the required pressure. Once they had fin-
ished with their activities, the pressure of the air lock was reduced again and
they went 'home' in the shuttle. At the time of the switching of the cutters,
when the boring machines were positioned at the deepest point, the divers
remained under pressure continually for 2.5 weeks. Afterwards the decom-
pression time lasted two and a half days. That was also the time that would
have been required if they would have had to be transported out in a case
of disaster. That is why all divers had undergone a diving-medical training
beforehand, which includes an annual stint in a hospital. That is where,
The divers' habitat,
where they remained
under pressure for
longer periods
Fig. 11.30
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