Reinforcing compressible soils by rigid inclusions is a method to reduce and homogenize settlements under many types of structures. A granular mattress, located between the structure and the group of piles, transfers part of the loads on the surface to the head of the piles anchored in rigid substrate. An experimental device, a mobile tray, has been especially designed in order to allow a better understanding of this reinforcement technique. This mobile tray simulates the settlement of the soft ground (not present here) located between the piles. With this device, a parametric study of the loadtransfer mechanism in the mattress is conducted in centrifuge at 20g. Loads at the top of the piles and settlements at different places above the granular mattress are measured during the the mobile tray going down. A possible way to improve this reinforcement technique is to insert a geosynthetic layer between the head of the piles and the granular mattress. In centrifuge, due to scaling laws, the choice of the geosynthetic has to be taken very carefully. Tests with and without geosynthetic are performed for different thicknesses of granular mattress. Then the improvement of the load-transfer mechanism by the addition of a geosynthetic is studied in centrifuge.