Civil Engineering Reference
In-Depth Information
Fig. 5.1
Various fire curves
1400
1260
4
1350
1200
1300
1300
1200
3
2
1200
1080
1029
1200
1080
1078
1068
1000
1014
986
928
867
925
1
800
822
761
4
3
RWS curve
RABT curve
658
600
556
2
Hydrocarbon (EC1)
482
400
1
Standard (ISO-834)
200
0
3
5
10
20
30
40
50
60
70
80
90
10 0
110
120
Time (min)
therefore, that certain insulation materials do indeed perform well when the
other fire curves in the figure are dealt with, but they function inadequately
under the circumstances which occur during a fire in accordance with the
RWS curve. For the structural integrity of the tunnel - in relation to the dan-
ger of spalling concrete - it is particularly the rate at which the temperature
increases shortly after the coming about of the fire which is of importance.
Besides, the maximum temperature attained and the duration of the fire
play an important role.
Factors which are dangerous for the
structural integrity
In the period prior to the construction of the Westerschelde Tunnel the
amount of attention paid to the fire safety of tunnels (read: immersed tun-
nels) was confined to the reduction of the concrete strength and the tensile
strength of the reinforcement steel as a result of high temperatures. The
third factor - spalling - was simply not in the picture, because for immersed
tunnels, the lower concrete density hardly played any role (having been
proven in fire tests).
As a result of two fires in the Netherlands, being under a viaduct and a small
underpass, the factor was brought to the attention of the Directorate-
General for Public Works and Water Management and an investigation was
initiated. The potential seriousness of the phenomenon was confirmed
shortly thereafter, by a fire in the tunnel boring machine during the construc-
tion of the Great Belt Tunnel in Denmark (1994) and the fire in the Channel
Fig. 5.2
Damage to the Great
Belt Tunnel in Denmark
TBM tail
with brushes
Ring 1158
11 5 7
11 5 6
11 5 5
11 5 4
11 5 3
130 mm
170 mm
200 mm
200 mm
270 mm
Fire ring 1
2
3
4
5
6
Jack almost at the
end of the stroke
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