Static and Dynamic Characterization of Soil in a Reinforced Earth Wall

Reinforced earth walls 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 wall with vertical facing. In spite of a very development technology to build reinforced wall, of soil 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 as 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 Dr. For the dynamic characterization resonant column tests were performed, to evaluate the equivalent shear modulus Geq 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. 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.