In 2012, setec carried out the preliminary design of an experimental embankment intended to validate the reinforcement to be used under the
embankments of the SEA (South Europe Atlantic) HSL (High-Speed railway Line) in the Dordogne valley, near Saint André-de-Cubzac.
The experimental embankment was constructed between January and March 2013, and was instrumented to compare reinforcement by geogrids and inclusions with three different mesh sizes (1.6 m, 1.7 m and 1.8 m) with reinforcement test plot without geogrids but with pavers and inclusions (with a 1.6 m mesh). The observations, gathered during more than 6 months already under an embankment height including the effect of railway overload, confirmed that the project criteria (including settlement criteria) could be satisfied by each of the configurations tested. The test plots enabled optimization of the project in a difficult geotechnical environment. On this base, setec continued with the geotechnical detailed design of the reinforcement by inclusions and geogrids for all the embankments on the left
bank (total length 1400 m) and for the various technical blocks located either side of the civil engineering structures.
The preliminary design calculations carried out prior to the construction of the experimental embankment provided values for settlement and loads on the inclusion heads in good agreement with the measurements ; this also validated the mode for taking into account geogrids above a network
of inclusions, as introduced into the calculations performed using the Foxta software (Taspie+ module).