Civil Engineering Reference
In-Depth Information
Progressive development
At the beginning of May 2000 a 'roundness measurement' of the tail section
took place. From that, it appeared that for the westerly machine it involved
deformations (dents) in the order of 40 mm, whereas the deformations of
the easterly shield increased to a maximum of 50 mm.
The degree of roundness had been measured previously anyway. After a com-
parison of the new results to the previous data, it was noticed that the situ-
ation worsened rather quickly: it involved progressive development of the
deformations.The boring machines were situated at the deepest point of the
route and in view of the safety, activities were halted immediately.
Another argument to stop, was the possible danger that on further deform-
ations, the shield could clasp the tunnel rings entirely at any moment. Not only
would that lead to damage of the lining, it also meant that the boring machines
would then be completely jammed.
That is why it was decided to take measures to prevent further deformations
and to investigate if the shield would break. With regard to the latter it could
be concluded rather quickly that the shield would not collapse.
Fig. 11.4
Diagrammatic
representation of the
shield deformations
of the westerly tunnel
boring machine
(reflected in red) at
the location of ring 543
in respect of the
assumptive position
(black)
R543
Location
27
40
20
0
20
40
1
26
2
25
3
24
4
23
5
60
80
100
22
6
21
7
20
8
9
19
10
18
17
11
12
16
15
13
14
The Colossus of Terneuzen
One of the alternatives that was developed to solve the problem of the deform-
ations, was a so-called ring-reformer: a steel ring with a large number of
jacks around the circumference which had to be placed on the inside of the
tail shield.The idea was, that with this ring it was perhaps possible to undent
the shield. However, for an undenting operation it appeared that forces which
were too great were necessary, which would also perhaps have a negative
effect on the (steel) quality of the shield. Repair of the shield was not pos-
sible, but an option which remained plausible, was the counteracting of further
deformations. While other solutions were also investigated, the manufac-
turer of the TBMs (Herrenknecht) were therefore commissioned to make a
stabilization ring. The eventual result - an enormous structure of approxi-
mately 80 tons nicknamed 'The Colossus of Terneuzen' - was never used
however. The reason for this was, that the investigation into other avenues
provided other prospects for managing the problem.The alternative - more
about this later - appeared to have a major advantage in respect of the
'Colossus': less loss of time. The installation of the ring-reformer would
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