Centrifuge parametric study of the geosynthetic overlap for reinforced piled embankment

Geosynthetic-reinforced piled-supported embankments may require the use of several strips of geosynthetics. The overlap of two strips of equivalent geogrids, located at the bottom of the granular (Hostun sand mixture) load transfer platform of constant height, is studied. The methodology follows the physical modelling technique in Centrifuge. The instrumented small-scale models (scale 1/12th) are based on the use of the Mobile Tray Device in the Geotechnical Centrifuge of the Gustave Eiffel University. The width of the overlap (in the range between zero and the pile spacing) is studied, for three area ratios, in terms of efficiency (load transfer) and surface differential settlements. The objectives are: 1) to observe the behavior; 2) to understand the mechanisms; 3) to quantify the effects of the parameters studied on key design quantity for practice. Depending on the overlap, up to three successive mechanisms of deformation and load transfer are observed during the tests. For practical applications, the results provide a first set of bi-linear relationships for both the efficiency and the differential settlement versus the overlap width.