Their names are Trône, Bailli, Montgomery, Tervuren, OTAN, Cinquantenaire, Reyers-Centre and Louise-Stéphanie (a complex of two associated tunnels). These eight road tunnels, over 300 m long, are all equipped with jetboosters (longitudinal ventilation systems for the air flow).
The work is challenging since it involves road tunnels in high-density urban areas. To minimize the impact on mobility in Brussels, the work will be carried out exclusively during night-time closures between 10 pm and 6 am. Each morning, the tunnels will have to be operational again and open to traffic. Planning and phasing will be crucial.
The jetboosters are to be replaced by new, more efficient, reversible fan models (capable of blowing in both directions), each equipped with temperature and vibration sensors. Operators will thus be able to ensure equipment availability, and monitor equipment behavior using the multiple measurements taken. In the event of fire, or any other incident, they can then trigger the appropriate scenario for the situation in question.
”The ventilation system in a road tunnel has two uses,” said tunnel department manager Simon Van Raemdonck, ”smoke extraction and sanitary ventilation of exhaust gases emitted by vehicles, when there's a lot of traffic”.
-Sanitary ventilation to evacuate toxic gases is achieved by monitoring the levels of carbon monoxide (CO) and nitrogen dioxide (NO2), which are measured by specific sensors and linked to each tunnel's BMS. Ventilation is triggered as soon as defined thresholds are exceeded.
-Smoke extraction ventilation consists of 2 successive phases:
oA safety phase whose role is to limit air velocity in the tunnel and stratify smoke so that it remains at the tunnel ceiling. This phase enables users to evacuate to the tunnel's emergency exits. To achieve this, anemometers are placed in the tunnel. They activate certain booster jets in the appropriate direction to obtain the desired result.
oA smoke evacuation phase, triggered by the fire department, to fight the fire and protect the integrity of the tunnel structure as quickly as possible. This phase also prevents smoke from the burnt-out tube from flowing back into the healthy tube.
Smoke ventilation will be mainly combined with 2 systems already in use in Brussels tunnels:
-A thermometric fibre optic fire detection system capable of detecting a temperature threshold or a rise in temperature and enabling fires to be located with a high degree of accuracy.
-An Automatic Incident Detection (AID) system consisting of cameras and software incorporating artificial intelligence, which not only identifies pedestrians, stationary vehicles or cyclists, but also detects smoke very quickly. This then triggers the appropriate ventilation scenario.
“In the event of a major failure or equipment unavailability requiring on-site intervention, the operator sends our maintenance teams a breakdown request. If the situation is not critical, we intervene at night during a scheduled tunnel closure, to limit the impact on operations. If the situation is critical, our technicians intervene on an emergency basis, 24/7, in compliance with the contractual on-call schedule”, explained Simon Van Raemdonck.
In total, our experts will work on 134 jetboosters (distributed among the eight tunnels), install 501 sensors and roll out 213 km of power and control cables, over the three years of the contract.
