Experimental Study on Dynamic Modulus and Damping Ratio of Rubber-Sand Mixtures Over a Wide Strain Range

This paper systematically investigates the dynamic behavior of sandy soils mixed with recycled tire rubber over a wide strain range in the order of 10-5-10-2, using combined resonant column and cyclic triaxial tests for measurement of the shear modulus and damping ratio. The experiment integrates small-strain tests using a resonant column apparatus and large-strain tests using a cyclic triaxial apparatus. The results demonstrated that the addition of rubber particles significantly enhances the linear elastic properties of the host sandy soils and improves the critical shear strain from which the rubber-sand mixtures change from linear to nonlinear stress-strain behavior. The critical shear strain is therefore introduced as the function of rubber content (RC), to identify the influence of RC on the strain-dependent dynamic properties of the host sandy soils. Then, a well-calibrated prediction formula is applied in conjunction with the concept of binary packing material to describe the behavior of the host sandy soils with various RC. Remarkably, the obtained normalized shear modulus and damping ratio vs. shear strain relationships address the limitations of existing testing methods to simultaneously capture the soil dynamic properties at low-strain (stiffness) and the large-strain (energy dissipation) regimes. The model constants can be simply determined through a unique set of explicit expressions which incorporate some basic index properties of the host sand and recycled tire rubber. In this regard, the proposed procedure provides a significant advantage in the evaluation of strain-dependent dynamic properties of rubber-sand mixtures in practice.