FEM investigation of full-scale tests on DSSI, including gravel-rubber mixtures as geotechnical seismic isolation

Soil-rubber mixtures underneath foundations are an eco-sustainable and low-cost Geotechnical Seismic Isolation (GSI) solution. Using rubber grains from end-of-life tyres in the mixtures can provide a modern recycling system that reduces the stockpile of scrap tyres worldwide. In recent years, gravel-rubber mixtures (GRMs) properties have been investigated, finding good behaviour in static and dynamic conditions. Laboratory tests on GRMs advantages as GSI in the form of a layer underlying the foundation of a structure are available in the literature. Nevertheless, only one experimental campaign on a full-scale prototype structure resting on GRMs with 0% and 30% rubber content per weight was performed (SOFIA-SERA Research Programme). This paper presents 3D advanced nonlinear FEM analyses to reproduce and furnish new results about the above-mentioned full-scale test. The calibration of the parameters of the different constitutive models used for modelling the foundation soil and the GRMs was supported by an extensive geotechnical characterization. The developed FEM model was validated by the results from the above-mentioned full-scale test in terms of accelerations and velocities. Then, the dynamic behaviour of the GRMs was studied, also considering the shear strains versus the shear stresses and the horizontal and vertical displacements, quantities not investigated experimentally. Finally, the GRMs static behaviour was also investigated, considering the GRMs axial strains and the GRMs and foundation vertical displacements. The paper highlights the fundamental role of both experimental tests and numerical modelling, as invaluable tools for coupled analyses of the seismic behaviour of soil-structure systems, including innovative materials, such as GRMs, and the main advantages of using GRMs as GSI.