The N31 is the direct (road) connection between Amsterdam and Leeuwarden in the Netherlands, via the Afsluitdijk and Harlingen. The road to, and through, Harlingen is still a single lane of traffic in each direction at ground level. The new N31 will become a motorway with two double-lanes and will be mainly deepened for about 2 kilometres.
The projected new road will be approximately 4.60 m to 10 m below surface level. And for this purpose, to a large extent, an open reinforced concrete structure will be created. After installation of the the sheet-piles, excavation will take place to approximately 2.50 m below ground level. After pile-driving, the prefab piles will be driven deeper with the help of a follower. Subsequently, the supporting struts will be placed in position so that the construction pit can be dug out to the necessary final depth. At the deepest areas of the access ramps, underwater concrete will be placed and the sheet-piling will be secured with grouted anchoring.
Crossing the Van Harinxmakanaal will be done by means of an immersed tunnel which will first of all be built in the access ramp. After construction, this element will be floated in the construction dock, dragged and immersed at its final location in the Van Harinxmakanaal.
GEO2 Engineering B.V. provides geotechnical design capacity to the design team, most specifically for the deep access ramps and the aqueduct. Specialised disciplines in this regard are the geotechnical design of the immersed tunnel, the design of a foil construction and the design of deep construction pits with tension piles. In addition to this, GEO2 is involved in the implementation design and in collaborating in the optimisation of the various stages.