Dimensioning the Rijnland Route

The Rijnland Route forms a new link between Leiden and Katwijk. A new tunnel, the Corbulo tunnel, has been built, and a new road, the N434, will be constructed. Sections of the N206 will also be modified and improved. On behalf of the contractor consortium Comol5, Iv carried out the dimensioning for the construction of the N434, the new east-west link between the A44 and A4 motorways near Leiden, and the 2,200-metre-long Corbulo tunnel. The tunnel is approximately 30 metres below ground and is largely hidden from view due to its deep location.

The Leiden area has a 6-metre-thick peat layer, meaning the ground can subside easily. The ground level was temporarily lowered during construction, followed by a gradual and controlled return to the original water level. This was particularly important for the deeply recessed position of the Corbulo tunnel to ensure that the ground beneath the tunnel was stable. The excavators quickly encountered water during construction, even though the work was conducted fifteen metres below ground level. The project covers a large and complex area in terms of the construction site and the number of critical borings for the tunnel. The area comprises houses, football pitches, golf courses and high-voltage pylons. Boring must be carried out safely under these structures without causing damage to the surrounding area.

The Rijnland Route is being developed to strengthen the region’s economy and improve both accessibility and the quality of life in the area. The Rijnland Route aims to improve traffic flow around the A44 and A4 motorways, which are often congested. A tunnel with sunken box structures at the entrances is the best solution both ecologically and in terms of infrastructure. It is also a solution that is visually acceptable to local residents.