Civil Engineering Reference
In-Depth Information
Monthly production
Fig. 11.26b
Progress of the boring
process
450
TBM east rings
TBM west rings
Total rings
KMW schedule
(rings per tube)
400
350
300
250
200
150
100
50
0
Fig. 11.27
Arrival of the tunnel
boring machine
Diving activities
Introduction
Never before had boring taken place with a slurry shield at such a great
depth (60 metres
NAP) and under equally (soft) soil conditions as for the con-
struction of the Westerschelde Tunnel. It was known beforehand that divers
would regularly have to be at the excavation front, sometimes even in front
of the cutting wheel for inspections and the carrying out of maintenance
activities, such as the switching of cutting teeth. Prior to diving operations,
the space between the cutting wheel and the excavation front was 'cleared' of
bentonite suspension - if the situation so permitted.The bentonite slurry was
pumped away up to a certain level while at the same time the compressed
air took over the support of the excavation front. Thus an air bubble was
created in which the divers, who entered the excavation chamber via an air
lock, could carry out their work. However, working in compressed air was
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