FEM dynamic analyses of soil-structure system with well-graded GRMs as GSI

Recent developments in End-of-Life Tires (ELTs) reuse emphasize their value in civil engineering applications. Shredded rubber, when mixed with soils to form Soil-Rubber Mixtures (SoRMs), is particularly promising for Geotechnical Seismic Isolation (GSI) systems. Previous studies with poorly graded soils have confirmed the effectiveness of SoRMs through laboratory and field investigations, but their preparation requires expensive grain-size selection. Alternatively, well-graded soils provide a more practical and economical solution for SoRMs, while preserving good mechanical performance. This research investigates the seismic efficiency of GSI systems employing mixtures made by well-graded gravel and rubber from End-of-Life Tires (wgGRMs) applied underneath a historical bell tower in Bronte (Catania, Italy). Finite Element Method (FEM) analyses were conducted on the fully coupled soil–wgGRM–structure system, employing advanced constitutive models. Specifically, the Hardening Soil with Small Strain Stiffness (HSsmall) and the Generalised Hoek–Brown (GHB) models were adopted to represent nonlinear soil and mixture behavior. FEM analyses of laboratory tests on the wgGRMs were performed for the calibration of the HSsmall model parameters. Dynamic parametric analyses explore different GSI layouts, rubber contents, and seismic inputs. Results confirm the effectiveness of wgGRMs, highlighting their potential as cost-efficient materials for the seismic protection of slender, heritage structures.