An Immersed Tunnel, better than a Long Span Bridge?

Traditionally long span bridges are applied for river crossings and often in delta areas and in soft soil conditions. As an alternative to a bridge, in countries like the US, Japan and the Netherlands many of these fixed links have been constructed as a tunnel with the immersed tunnel technique. In these countries this technique is quite mature and common practice. However, over the past years there is also a growing interest for this technique in other countries. Recent tunnel projects have shown that immersed tunnels are feasible and competitive to a long span bridge under more challenging circumstances. Immersed tunnels have been constructed successfully in water depths up to 58 m below sea level, in very poor soil conditions, with increasing lengths, increasing design lives and in offshore conditions.