MARMARAY TUNNEL, ISTANBUL

Marmaray has been described as the project of the century, and the tunnel will connect two continents with the rail-tunnel running deep beneath the Bosphorus Straits in Istanbul. The tunnel consists of a series of earthquake-proofed immersed tubes, assembled from 11 sections, each 130 metres long and weighing up to 18,000 tons. These are placed down to 55 metres below sea level, making it the world’s deepest undersea immersed tunnel tube. When in full operation it is expected that around 1.5 million passengers will cross the Bosphorus Straits.

Acrefine Engineering has provided technical support to FlaktWoods, UK, who is supplying a range from their super-powerful axial fans for eight shafts ventilating the new crossing. Measuring up to 2.8 metres in diameter, the fans will be capable of providing emergency ventilation in the worst-case scenario – a fire on a freight train more than a kilometre long.

Earthquake protection is a key factor in this scenario and Acrefine is assisting with expert advice and consultancy to achieve best practice. Beside the local Turkish code, FEMA is also used for compliance with the latest international standards in seismic.

Seismic and anchor calculations are performed to provide secure mounting for the fans, which are classified as critical, i.e. life safety equipment. New heavy duty AS-AR-10000 reinforced type seismic snubbers, specifically designed and manufactured to restrain large equipment, have been used in this project. Each fan will be mounted with four seismic snubbers that can resist the highest earthquake loads.