Thermoelastic Enhancement of Damping of Sand Using Synthetic Ground Rubber

This paper examines the possibility of introducing synthetic rubber in constructed earthen systems to improve their vibration attenuation. The results of a series of controlled laboratory tests—aimed to investigate the improvement of low-strain dynamic properties of Ottawa sand by mixing ground rubber of similar size—showed a simultaneous increase in both the shear modulus and the damping ratio of the sand specimens up to an optimum volume proportion of the rubber. Predictions using Hertzian particle contact effects and mechanical damping, resulting from thermoelastic effects between the dissimilar particles, were employed to discern the observed behavior. It is postulated and examined through the available data that the large difference between the elastic modulus of the two materials results in the increase in contact area of the sand and rubber particles and consequently the increase in the stiffness matrix. Similarly, the large difference between the coefficient of thermal expansion of sand and rubber may effectively lead to high thermoelastic enhancement of damping in the sand-rubber mixture.