Dynamic Behavior of Sand/Rubber Mixtures, Part II: Effect of Rubber Content on G/G_O-γ-DT Curves and Volumetric Threshold Strain

This paper examines the strain-dependent dynamic properties (G/G_O-logγ-DT curves) of dry and saturated sand–recycled rubber mixtures in a range of shearing strain amplitudes from (5 × 10⁻⁴) % to (6 × 10⁻¹) % using a fixed-free torsional resonant column device. The effect of the rubber content on the pore water pressure buildup and volumetric threshold strain γ_t^v of saturated mixtures, as well as the effect of specimens’ geometry on the experimental data, are also presented and discussed. Based on a comprehensive set of experimental results, a modified hyperbolic model, frequently used in practice, has been proposed. An increase in the rubber content leads to a more linear shape of the G/G_O-logγ and DT-logγ curves and a reduction in the pore water pressure buildup. Damping is expressed in terms of DT-DT_O, which eliminates the effect of the rubber content and the mean confining pressure. The final aim is to propose appropriate design G/G_O-logγ-DT curves for sand–rubber mixtures currently used in practice.