Mechanically Stabilized Earth Walls (MSEWs) and Reinforced Soil Slopes (RSSs) are cost effective soil-retaining structures, that can tolerate much larger settlements than reinforced concrete walls. By placing tensile reinforcing elements (inclusions) in the soil, the strength of the soil can be improved significantly, allowing to build safely, even in a severe seismic areas, high steep slopes and vertical walls. In spite of a very development technology to build reinforced wall, the soil characterisation to fill the back on the wall is some time very poor.

The paper presents the geotechnical characterization of two kinds of sandy soils taken from the backfill of a reinforced earth wall, build has a prototype in Brazil.

To define the mechanical behaviour of Brazil sand a large number of static and dynamic laboratory tests were performed on dry reconstituted specimens. The static tests include direct shear tests performed on specimens reconstituted by the pluvial deposition method with different relative densities D_r.

By means of direct shear testing the shear strength parameter j was computed, paying attention to its relationship with the relative density D_r. For the dynamic characterisation of the backfill Resonant Column test were performed, to evaluate the equivalent shear modulus G_eq and damping ratio D. The soil non linearity due the decreasing of shear modulus and the increasing of damping ratio with shear strain was evaluated. The dry reconstituted samples were subjected to an initial isotropic confining pressure able to simulate in situ effective stress status.

An accurate static and dynamic geotechnical characterisation of the backfill is required to perform the analytical modelling to predict the mechanical behaviour of the reinforced wall.