Experimental and theoretical analysis of the seismic risk mitigation through interventions on soil with synthetic materials

The PhD thesis has been finalized to study the influence of synthetic materials on propagation of waves coming from earthquakes; since soil modifies seismic waves in terms of maximum acceleration and frequency content, how underground inclusions affect the propagation has been focused by the work. Materials analyzed have been polyurethanes, i.e. cellular polymers widely applied in different fields; from a geotechnical point of view, they are mainly used for settlement reduction or consolidation of foundation soils. Polyurethanes have been first studied under static and cyclic loads, by performing oedometric, triaxial and resonant column tests, in order to analyze their behavior for geotechnical tensional states. The thesis aim has been focused after the realization of an experimental system for unidimensional wave propagation studies, consisting of a containing box, where impact hammer tests have been performed. The experimental set-up has been theoretically and numerically calibrated on sandy specimens; composite specimens have been then realized. Polyurethane has been included in slab form, showing reductions of recorded accelerations increasing with width, for such impacts that accelerometer stability is guaranteed. For higher energy impacts, the experimental system has shown its limits, confirmed by theoretical modeling. Inspired to Deep Injection technology, polyurethane has been injected in soil, by means of syringes; however, this solution does not allow to realize in-pressure injections, typical in soil intervention techniques. A numerical model, calibrated on the experimental results, has allowed to numerically deepen the experimental campaign, analyzing further aspects, difficult to be experimentally investigated because of practical efforts and limits.