N222 Roundabout upon EPS Embankment with Integrated Corrugated Steel Tunnel Structure Without Pile Foundation

Abstract

In April 2015 on a location with settlement sensible subsoil surrounded by greenhouses and water channels a large roundabout has been realized using 25,000 m³ EPS geofoam blocks. The roundabout is a part of the regional road N222 which connects Flora Holland (a huge marketplace for floriculture) with the nearest highways. The region is characterized by the largest greenhouse concentration in Europe. Due to its important economic function more than 11,000 vehicles pass the new roundabout over the lightweight embankments daily. During construction, unimpeded traffic passage had to be guaranteed. Bellow the roundabout a tunnel for the passage of bicycles was designed. Adjacent power line pylons made it impossible to place pile foundations as conventionally used in Dutch areas with peat subsoil. Consequently a structure using concrete tunnels was not an option. Therefore a 3.7 m high egg-form corrugated steel tunnel structure without pile foundations was integrated through the EPS embankment. The applied tunnel system with 7-mm-thick corrugated steel plates supports lightweight foamed concrete built in around. The tunnel structure is settlement free without pile foundations. Additional advantages include its lower building costs compared with conventionally designed tunnels made of concrete. Finally, the construction time was reduced thanks to this innovative design method. The paper deals with the design aspects related to the N222 roundabout structure with the lightweight embankments in general, and with the implemented tunnel solution in particular.