N222 Roundabout upon EPS Embankment with Integrated Corrugated Steel Tunnel Structure Without Pile Foundation Milan Duškov and Jeroen Tameling 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 Keywords Project case Lightweight embankment Innovative tunnel design Integrated tunnel construction Corrugated steel tunnel structure No pile foundation M Duškov (&) InfraDelft, Delft, The Netherlands e-mail: milan.duskov@infradelft.nl J Tameling Waalpartners, Naaldwijk, The Netherlands © Springer International Publishing AG, part of Springer Nature 2019 D Arellano et al (eds.), 5th International Conference on Geofoam Blocks in Construction Applications, https://doi.org/10.1007/978-3-319-78981-1_25 309 310 M Duškov and J Tameling Introduction As part of improving the accessibility of greenhouse horticulture, and to stimulate restructuring of the Wateringveldse Polder region, a new connection road has been realized by the municipality of Westland near The Hague Within that framework, a double-lane roundabout was realized at the junction of the Wateringveldse Polder accessing the regional road N222 (so-called Auction Route) In order to connect the roundabout, a height difference of about 5.5 m had to be realized The new roundabout was finished in mid-April 2015 This project had a variety of complex (boundary) conditions During construction, traffic on the regional road N222 had to have virtually unimpeded passage due to the economic function of the nearby auction To minimize the settlements despite very weak subsoil layers, a total of approximately 25,000 m3 of EPS was used under the roundabout and in the adjacent road embankments The project location is characterized by flat polder land and shallow groundwater and it is enclosed between adjacent greenhouse horticulture and the regional access road Further, west of the new round about, the N222 crosses over a 10 m wide canal (called Lange Watering) A new bridge was constructed next to the existing one (Fig 1) A new recreational bicycle connection was also part of the project Because an additional connection over the water was not desirable, tunnel construction beneath Lange Watering cycling tunnel N222 new bridge Fig The realized double-lane roundabout between the Wateringveldse polder and the regional road N222 (=the auction route) N222 Roundabout upon EPS Embankment with Integrated Corrugated … 311 the roundabout and existing provincial road had to be realized However, a concrete tunnel with pile foundations would cause too much nuisance to the project, due to the longer construction time High-voltage masts were also in the way, inhibiting construction of conventional pile foundations, so a lightweight variant was considered in order to meet project restrains and to minimize settlements An original solution was designed and realized through the EPS embankment The bicycle tunnel includes mm thick corrugated steel sheets with a foamed concrete enclosure integrated into the EPS embankment Such a prefabricated tunnel system is cheaper and constructable in a shorter period of time than a tunnel made of concrete because no pile foundation is needed The municipality of Westland was the owner of this multidisciplinary project, which was coordinated from planning and contracting up to the design by Waalpartners Civil Engineering The specialists of InfraDelft (responsible for the lightweight road embankments, pavement structures and the tunnel design) and Bergschenhoek Civil Engineering (responsible for the tunnel construction with the corrugated steel sheets) took care of engineering This paper describes the boundary conditions, selection method for settlement reduction during the design process and the unique integrated bicycle tunnel construction Complex Boundary Conditions and Trade-Offs Characteristic of the project is the diversity of design challenges As the Cone Penetration Test results explicitly pointed out the roundabout location had an evident problem related to thick compressible peat layers Implementation of traditional preloads within the available construction time was not possible due to the presence of adjacent greenhouses and the regional access road A bridge height of about 5.5 m had to be realized Also, the regional road N222 to the west of the new roundabout is crossed underneath by a 10 m wide water canal (Lange Watering) Furthermore, the high voltage masts and the local ‘peat quay’ (‘veenkade’), within the boundaries of the project, were factors that had to be considered Finally, traffic on the N222 to nearby Flora Holland auction could not be hindered during construction (Fig 2) During the design process, an evaluation was made between possible consolidation mitigation approaches such as implementation of (a) conventional preloading, (b) vacuum method, (c) ‘lightweight’ granular materials, (d) piled supported embankments and (e) EPS embankments Based on the extent to which the evaluated options have influence and/or limitations, the choice was reduced to a further elaboration of three variants These elaboration methods have been assessed on the following factors: occurring settlements, consolidation period, influence/damage on the ‘peat quey’ (‘veenkade’), environmental impact, implementation restrictions and costs The evaluation finally pointed out that the use of the EPS blocks was the overall, including economically, the best solution for this project The solution does not provide the lowest construction costs but scores very well on other factors, 312 M Duškov and J Tameling Fig Characteristic cone penetration test (CPT) results for the project location including maintenance costs Given the economic importance of minimizing traffic interruption delays, the municipality of Westland chose the variant which included implementation of EPS geofoam blocks During the project process, the municipality of Westland added the recreational bicycle link to the scope This decision created a design challenge regarding not only technical and financial aspects, but also the realization of such a connection An additional bridge connection over the canal was not desirable, so a connection through the future roundabout and existing provincial road embankment became the economically most interesting solution Still, a concrete tunnel was practically not constructable Therefore, lightweight variants were investigated which could prevent settlement differences between the existing and new road parts and could be quickly constructed N222 Roundabout upon EPS Embankment with Integrated Corrugated … 313 Lightweight EPS Embankments The height difference between the lower part of the ground level and the highest point in the center of the roundabout is more than m The local soil is notorious for its settlement sensitivity due to the thick peat and clay layers The exceptionally high percentage of freight traffic on this Auction Route made the design of such a high roundabout embankment at this location with such unfavourable soil conditions even more challenging Indeed, the amount of freight traffic had consequences for the asphalt pavement thickness, which was unfavourable to the weight of the pavement structure Thanks to the ultra lightweight EPS blocks used (approximately 25,000 m3), the vertical load on the subsoil was reduced to a great extent This also minimized the settlement-related consequences for neighboring objects Optimum dimensions of the realized EPS embankment were determined iteratively from finite elements analysis using Plaxis models By using these sophisticated models the expected stress values within the relevant roundabout and road embankment profiles were also controlled Additionally, those calculations enabled the use of a less expensive type EPS in the embankment parts where lower stress values are expected (Figs 3, and 5) Unique Design for Lightweight Cycling Tunnel Construction In order to design a settlement-free tunnel integrated in the EPS embankment of the roundabout, the arching principle was used The tunnel system used 7-mm-thick corrugated steel plates supporting lightweight foamed concrete The modular system of corrugated steel sheet elements without a pile foundation fulfilled the specific project requirements of free space for cyclists and pedestrians and suitability for the expected traffic load over the tunnel In terms of both building costs Fig Plaxis model of a representative profile of the regional road N222 314 M Duškov and J Tameling Fig Lightweight EPS-geofoam embankment (in the north) of the access road and the roundabout of the N222 Fig Lightweight EPS-geofoam embankment (eastward) of the roundabout of the N222 and construction time reduction, the system offered advantages The high-voltage masts also made it impossible to use a conventional pile foundation necessary for a concrete tunnel alternative The oval tunnel system is based on the load distribution by normal force along the “pressure points” in the steel shell construction According to the Klöppel & Glock method, interaction between the thin corrugated steel wall of the tunnel and the support pressure—generated by the surrounding mass—was considered As an alternative to the standard design with compacted sand around the culvert, adequate side support is ensured by a lightweight foamed concrete enclosure combined with stronger EPS blocks There were no technical restrictions regarding either the profile or the traffic load over the considered tunnel system In the strength calculation, the tunnel was tested in three aspects N222 Roundabout upon EPS Embankment with Integrated Corrugated … 315 Fig Construction of the corrugated steel sheets tunnel under the N222 • Both the arch of the profile and the joint plate connections had to be sufficiently strong • The weight of the cover on the tunnel construction had to be sufficient to provide adequate back pressure when maximum traffic loading passes over • The foamed concrete enclosure had to be sufficiently strong (Fig 6) Considering this project, the lightweight character of the tunnel construction including the foamed concrete enclosure was essential Obviously, conventional sand fills would lead to unacceptable settlements A newly developed design methodology offered a cause oriented solution A reference project did not exist because such a design solution had never been realized before (Figs 7, and 9) The entire tunnel design has been calculated using Plaxis models for various representative profiles Plaxis models were used to analyze and optimize the behaviour of the N222 bicycle tunnel section In this way, the effects of applying a variety of foamed concrete and EPS types were calculated to figure out adequate tunnel designs (Fig 10) Fig Assembling the corrugated steel sheets 316 M Duškov and J Tameling Fig The corrugated steel sheets covered by the membrane before pouring the foamed concrete enclosure of the cycling tunnel Fig Plaxis model upper part with the EPS fill under the auction route (N222) and a foamed concrete enclosure around the cycling tunnel Fig 10 The auction route (N222) with the cycling tunnel in service N222 Roundabout upon EPS Embankment with Integrated Corrugated … 317 Conclusion The realized road constructions for the Auction Route (N222), with the cycling tunnel below, complies with the project requirements including the required design life This tunnel design method for modular steel elements integrated in the EPS fill is an ingenious but multi-beneficial solution The tunnel system with 7-mm-thick corrugated steel sheets and a foamed concrete enclosure was more cost effective than a tunnel made of concrete because no pile foundation was required ... auction route) N222 Roundabout upon EPS Embankment with Integrated Corrugated … 311 the roundabout and existing provincial road had to be realized However, a concrete tunnel with pile foundations... was tested in three aspects N222 Roundabout upon EPS Embankment with Integrated Corrugated … 315 Fig Construction of the corrugated steel sheets tunnel under the N222 • Both the arch of the profile... service N222 Roundabout upon EPS Embankment with Integrated Corrugated … 317 Conclusion The realized road constructions for the Auction Route (N222), with the cycling tunnel below, complies with