Immersed tunnelling

Executive Director and immersion commander Martijn Smitt, who specialises in immersed tunnels, has been involved in numerous multidisciplinary, international construction projects for over two decades. Amongst them over 15 immersed tunnel projects. As one of the few in the world, he is acknowledged as one of the world’s leading experts and he knows how to combine the complex immersed tunnelling technology with the dynamics that come to the immersion process. He explains: “Because of the high buoyancy, we can float tunnel elements in a controlled manner, using Archimedes Law. By using a system combining winches and pontoons we are able to position the tunnel element with high precision. Although the lifted weight is very low, the mass varies between 25,000 and 60,000 tons. Controlling that amount of mass that is moving dynamically underwater is complicated. Depending on the location, each immersed tunnel has, for example, to deal with different currents, weather conditions, tides, waves and salinity, and sometimes we even have to take the influence of seiches into account. Managing the dynamically moving mass combined with these complex conditions requires complex calculations and smart techniques.”