GEOTEXTILE REINFORCED MOTORWAY EMBANKMENT OVER INDUSTRIAL WASTE, AULNOIS SITE, FRANCE

This case history shows the technical and economic effectiveness of a combination of geotextile techniques and the use of an ultra-light material for an embankment of the A26 motorway at Aulnois, France. Here, the motorway crosses an alluvial area, consisting of compressible soils about 3m thick. Its route includes a settling pond for mud washed from sugar beets. For a 320m stretch, the pavement was planned 7m above the existing level of the heterogeneous wastes, about 6m thick. The chosen solution had the following stages: (1) partial punching of the compressible soil; (2) preloading; (3) unloading the embankment to a certain level; (4) constructing a light embankment, to support the pavement at its final level. The 6.5m punched embankment had to be reinforced, to ensure the embankment's integrity during punching and its stability during later consolidation. The reinforcement consisted of two layers of Enka 200 polyester woven geotextile, with tensile strength 200kN/m and working tensile force 100kN/m per unit width. An experimental embankment was built to refine the final design. The motorway embankment's performance since 1987 has been excellent. For the covering abstract see IRRD 865821.