Characteristics of rubber-sand particle mixtures according to size ratio

In this study, rubber-sand particle mixtures are investigated to understand their stress-deformation and elastic modulus characteristics. Specimens are prepared with various size ratios, sr (=D_rubber/D_sand), between sand and rubber particles, and different volumetric sand fractions, sf (=V_sand/V_total). Small strain shear waves are measured under a K_o-loading condition incorporated with the stress-deformation test by using an oedometer cell with bender elements. The stress-deformation and small strain shear-wave characteristics of rigid-soft particle mixtures show the transition from a rigid particle behavior regime to a soft particle behavior regime under a fixed size ratio. A sudden rise of the Λ factor and the maximum value of the ζ exponent in G_max=Λ^{(σ_o'/kPa)ζ} is observed at sf≈0.4-0.6 regardless of the size ratio (sr). The transition mixture shows a high sensitivity to the confining stress. The volume fraction for the minimum porosity may depend on the applied stress level in the rigid-soft particle mixtures because the soft rubber particles easily distort under load. In this experimental study, the size ratio and volumetric sand fraction are the important factors which determine the behavior of rigid and soft particle mixtures.