GEOSYNTHETIC supplier Huesker has used a geotextile to provide the foundation and to limit the land take of a bridge approach embankment in Germany.
The bridge carries the new B111 road over a railway line near the village of Mahlzow on the island of Usedom, on Germany's north east coast.
A site investigation showed the soil in the western ramp area contained peat layers and was prone to settlement. The area is also protected rare marshland so embankment design had to limit land take.
Without foundations it was calculated that the 7m high embankment would settle 220mm, which was obviously unacceptable.
Final design incorporated 800mm diameter vibrated concrete columns installed to 7.6m. Two layers of uniaxial geotextile support the structure between the columns in areas not carried by the arching effect, as well as taking up the spreading forces at the lower level. The polyester geotextile has a tensile strength of 100kN/m and was placed in two layers at 90infinity to each other.
The sand fill embankment has a 63infinity slope and is reinforced using geogrid at 0.5m spacing with an anchorage length of 6m and a wraparound upper return of 2m.
Rooted cuttings were planted between the reinforcement layers during construction before hydroseeding was carried out to give a grass finish.