Small strain behaviour of a lime treated silty sand

Road construction often involves big amount of waste soils. With the growing concern for environment, the re-use of those soils as construction materials is spreading. Waste soils have poor mechanical properties and need to be improved in order to be used as construction material. Lime treatment is often adopted to improve stress-strain behaviour of soils usually in the embankment construction. At University of Naples an extensive project is in progress to evaluate the use of lime treated soils as seismic geomaterial attenuation system. In this paper the results of an experimental investigation, carried out to analyse the influence of lime addition on the pre-failure behaviour of a silty clayey sand, will be reported. The soil used for this study is from Parco del Cilento, 100 Km south of Napoli. Soil treatment was made by compaction and adding different amount of lime. To investigate the mechanical behaviour of the compacted material and the influence of lime addition monotonic, cyclic and dynamic torsional shear tests have been carried out using a RCTS apparatus. Tests have been performed on specimens compacted at different moisture water content of untreated and treated soil saturated at constant volume. Influence of moulding water content and lime addition have been analised in terms of initial shear modulus and damping ratio and their variation with confining stress, strain level and curing time. From experimental data, it was observed that lime addition induces an increment of stiffness and a reduction of damping ratio. The effectiveness of lime addition depends on the moisture water content and grow up with curing time.