Woven geotextile reinforcement embankments on piles
Location of work/project:
Reeuwijk - The Netherlands
Geosynthetic reinforcement offers technical, cost effective and environmentally friendly alternative to traditional solutions. Particularly on soft soil, basal reinforcement of piled embankment with woven geotextile limit the use of fill material (no need of berms or preload), reduce the construction time and post construction deformation.
Reeuwijk is a small village in South Holland, in the central part of the Netherlands and was established as a good location for peat harvesting. Indeed, the subsoil consists of 8 m very soft and compressible peat and organic clay deposits, with a groundwater table as high as 0.2 to 0.5 m below ground surface.
To improve the capacity of the existing road but also limit the consequence of the traffic downtown, a 3.5 km bypass road was constructed around the village. The road is 10 metres wide and has one lane in each direction, with extra lanes at junctions.
To build a road and a bicycle path in parallel, with these very poor ground conditions, construction method needs to be selected carefully. A traditional construction method consisting of a sand embankment was investigated as it is generally considered as an economical solution. However, this technique would have induced large deformations in the extremely soft, compressible soil and affected the underground infrastructure along the new track. It was shown that, in this case, an embankment of sand with vertical drainage is more expensive than applying a basal reinforced piled embankment.
The solution retained was a basal reinforced piled embankment with precast concrete piles driven into the firm substratum. The geosynthetic reinforcement was placed at the embankment base. The fill material consisted of recycled crushed demolition waste aggregate, mainly concrete, with a friction angle of 35° and the total embankment height was H = 1.20 m.
The design of the whole structure followed the Dutch design guideline CUR 226 (2010) and incorporated two layers crossed of a woven geotextile, TenCate Geolon® PET400 across the tops of the pile caps. The strengths were determined based on allowable design loads, strains and required design life.