Dynamic properties of polyurethane from resonant column tests for numerical GSI study

The paper focuses on the detailed analysis of the dynamic characterisation of polyurethane to evaluate the effects of polyurethane injections into soil with the aim of geotechnical seismic isolation. To determine the dynamic properties, resonant column (RC) tests were performed at the University Kore of Enna (Italy) on specimens of pure polyurethane with different values of density and subjected to different mean confining pressures. The results obtained by means of RC tests, in terms of shear modulus G and the damping ratio D as a function of shear strain gamma(c), allowed to develop an analytical formulation for G-gamma(c) and D-gamma(c) curves, taking into account the linear relationship with density, of both the maximum value of shear modulus G(max) and the minimum value of damping ratio D-min. The analytical formulation derived from the experimental results is applied for ground response seismic analyses of cohesive soils injected with polyurethane, using a finite element code. The numerical results show that the polyurethane injections reduce the value of maximum acceleration on the ground surface and the reduction varies with the thickness of the soil modified by polyurethane injections.

Automated summary

The paper focuses on the dynamic characterization of polyurethane in order to evaluate its effects on geotechnical seismic isolation when injected into soil. Resonant column tests were conducted on pure polyurethane specimens with varying densities and subjected to different mean confining pressures. The results were used to develop analytical formulas for shear modulus and damping ratio, taking into account the relationship with density. The analytical formulas were then applied in seismic analyses of cohesive soils injected with polyurethane using a finite element code. The numerical results demonstrate that polyurethane injections reduce the maximum ground surface acceleration, and the reduction varies with the thickness of the soil modified by polyurethane injections.