Ringtrac Geotextile Encase Sand Colums as foundation system for a 2.4 km long dyke
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Summary:
Germany – Hamburg
HUESKER Synthetic GmbH
Approximately 60.000 pieces of Ringtrac® Geotextile Encase Sand Columns (GEC) were installed at Mühlenberger Loch in Hamburg as a foundation system for a 2.4 km long dike. Amongst other things, the GEC solution saved 35,000 tonnes of sheet piling and more than one year of construction time comparing to the original design solution.
The new dike encloses a polder creating 140 ha of new land for the extension of the existing DASA Airbus plant (EADS) in Hamburg-Finkenwerder, required for the production of the new Airbus A 380. This enclosed area required to be raised up to 3 m above seal level. The main problem faced was construction in very soft soil
(cu between 0.4 and 10 kN/m2) with thicknesses between 8 and 14 m. The area concerned is also located in a tidal zone, with soil movement into the Elbe river not being permitted.
The original design solution for solving the stability problem asked for a 2.5 km long sheet wall to a depth of 40 m. The GEC, alternative solution, saved 35,000 tonnes of sheet piling, 15 ha of reclamation area, 1.1 million m3 of sand filling, 8 million litres of fuel consumption and more than one year of construction time.
The Ringtrac® geotextile casing with a diameter of 800 mm provides radial support to the sand column in the soft layers. The distance between the columns centres is generally between 1.7 and 2.4 m. Over the GEC a horizontal bearing and equalising reinforcement Basetrac® Duo is installed. Before construction of the dike is undertaken. Over the enclosed area both Fortrac® geogrids and Stabilenka® geotextiles were used as horizontal reinforcement. The main advantages of the system are the major savings in steel and sand transport as also the extensive reduction in settlements.