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Vous êtes Local Informations Applications Case Studies Tunnel de Cointe, Liege

Success story : Road Tunnel Protection

Area : Liège, Belgium
Road Tunnel Protection

 

Like many cities, Liege in Belgium is a hub for heavy lorries and vehicles on their way to other destinations within Europe. Over the last few years, the heavy traffic crossing the city from North to South and from East to West reached excessive levels and became a hazard. The engineers in the city transport department were given the task of finding a solution to this problem.

 

Liege is located in a valley, crossed by the river Meuse and surrounded by steep hills, because of this topology it was clear to the engineers that finding a solution was going to involve important and difficult civil engineering works.

Tunnel de cointe

The chosen plan involved building a series of structures: a tunnel, 376m long followed by a 480m underpass in the city, joined to a further tunnel of 635m, via a suspension bridge over the river some 327m long. This was then followed by a curved tunnel of approximately 1600m long.

 

The traffic flow along this new route was estimated to be 60,000 vehicles per day. Design considerations were given to the environment and the surrounding residents, in addition to the compliance with the necessary standards of safety for the construction of the tunnels and bridge.

 

The tunnels were provided with safety equipment comprising comprehensive signs (for guidance, safety etc) lighting, ventilation, surveillance and communication equipment, pollution control, fire protection, automatic incident detection and much more.

 

Safety was of paramount importance as an ordinary incident in a tunnel could assume dramatic proportions; fire and explosion being very real hazards.

 

Electrical power to the tunnels is supplied by a 500 kilometre low smoke and halogen free cable. All the equipment is dependant on the quality of the power supply and it is essential that in the event of a mains failure or in the case of a fire, the critical equipment continues to operate without detriment.

 

In order to secure 100% of the power supply in all situations, the engineers were asked to identify which loads were absolutely critical to ensure safe traffic movement through the tunnels especially in the event of a major incident.

 

Solution

The electrical loads were split and identified as critical and non-critical. The non-critical loads which could accept a short mains interruption whilst waiting for an alternative supply were ventilation and pumping station equipment, whilst critical loads which could accept no interruption were lighting, fire detection, exhaust vents/fans and all the equipment for communication purposes.

To guarantee a permanent, uninterrupted power supply to the critical loads, 4 x NO-BREAK E1 systems were installed in addition to an emergency standby diesel genset for the non-critical loads.

These machines are tested once a week and once a month a mains failure is simulated.

The 4 x NO-BREAK E1 systems are rated at 1000kVA  and each has sufficient fuel capacity to run for 48 hours.

The systems are placed in four different, conveniently chosen locations so as to be easily accessible but somewhat remote from the tunnels. To ensure their readiness to operate, the diesel engines are pre-heated and the rooms in which they are located are maintained at a constant temperature.

Since they are located in urban areas, much attention was paid to lower the noise levels from the exhaust outlets and reduce any noise nuisance to local residents. Residential silencers and widely dimensioned air inlet and outlet silencers were fitted to guarantee a comfort noise level compatible with the latest requirements.

An interesting feature of the system is that, when operating in normal mode, the NO-BREAK E1 provide a service to the user by injecting reactive power back to the mains, improving the power factor thus reducing the energy costs.