ROAD TUNNELS/SAFETY | SECTOR
100 120 140 160 180 200
0
D50-2.6 D50-1.6 D50-0.6 Activation End of test
20 40 60 80
0 010 20 Time [min] 30
100 120 140 160 180 200
20 40 60 80
40 010 0 20 Time [min] 30
100 120 140 160 180 200
20 40 60 80
40 010 0 20 Time [min] 30 40
Left, figure 3:
Fire test temperature graph - Temperatures at 50m downstream (D50) from the centre of the mock-up fire, and sampled at 0.6m, 1.6m, and 2.6m above ground level. Left graph: full-scale fire test; middle graph: CFD model validation; right graph: CFD simulation for the Samruddhi tunnel
For the design of the Samruddhi fire safety system,
Danfoss used its Computational Fluid Dynamic (CFD) models that replicate data from full-scale fire tests with the water-mist system to match with the size and requirements of the project tunnel. The CFD model can also be used to analyse if the ventilation capacity could be reduced and whether the safety of people, fire brigades, and the structure is still adequate. Temperature data were recorded at different locations
and heights during the full-scale first tests, such as shown in the graphs in the Figure 3, at a location 50m downstream (labelled D50) from the fire incident. The temperatures were sampled at three different heights (0.6m, 1.6m, and 2.6m above ground level), defined to cover the zone in which people evacuate or which could impact people’s ability to evacuate. It is clearly seen that the temperatures in the evacuation zone were at tenable levels during the
required period of time in the full-scale fire test, i.e., at least 10 minutes after the activation of the water- mist system. It can also be seen that the criterion for untenable conditions was not reached throughout the full-scale fire test. The CFD model validation replicated the trend from the full-scale fire test with 80%–90% accuracy, which means the model is considered a good, validated CFD model. The model is then applied in the design of the SEM-SAFE®
high-pressure water-mist system as
part of fire safety provisions in specific tunnel projects, such as Samruddhi (see Figure 4). For that project, the CFD simulation showed that the temperature in the evacuation zone can be kept well below untenable conditions thanks to the water-mist system as well as the tunnel cross-section being much larger than the one in which the full-scale fire test was conducted.
Above, figure 4: Samruddhi road tunnel, India July 2024 | 33
Temperature [°C]
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