Elastic Anisotropy of Tire Shreds

This paper deals with anisotropic elastic properties of large-size tire shreds used as lightweight fills in road and embankment construction. The anisotropy is a result of compaction and overburden pressure, which induce a layered structure of the shreds. Laboratory experiments conducted in a novel biaxial apparatus revealed a difference in Young's moduli perpendicular and parallel to the layered structure; also, Poisson's ratios differ although their values could not be determined accurately. The out-of-plane shear modulus not readily determined from the tests was assessed by means of a layered material model. The results were used for determining the settlement of two road structures containing a layer of tire shreds modeled as either an isotropic or an anisotropic elastic material. Numerical calculations using the code CIRCLY indicated that the effect of tire shreds' anisotropy on road structure settlements is moderate, and the traditional isotropic elastic analysis overestimates the actual settlements.