Effect of Stress Rotation and Intermediate Stress Ratio on Monotonic Behavior of Granulated Rubber-Sand Mixtures

The rotational failure of backfills and embankments is known to be involved with inhering anisotropic effects resulting from different stress paths along the rotational shear plane. The granulated rubber-sand mixtures have been lately used in embankments and backfills as light additives while their anisotropic effects are not well understood. This paper investigates the effect of stress rotation angle (alpha) and intermediate stress ratio (b) on shear strength and excess pore-water pressure (PWP) variations of granulated rubber-sand mixtures (GRSM) under undrained conditions using a hollow cylinder apparatus (HCA). Specimens are prepared using different percentages (by weight) of granulated rubber. The experimental results show that for a specific granulated rubber percentage, increasing alpha from 0 degrees to 60 degrees and/or b from 0 to 1 reduces the shear strength and increases PWP of GRSM. Moreover, by increasing granulated rubber percentage (up to 20%), the mixture becomes more isotropic, and the effects of alpha and/or b on shear strength degradations and PWP variations are reduced. The reducing effect of anisotropy is further investigated quantitatively through evaluating the rotational shear strength and failure potential of an embankment resting on a granulated rubber-sand mixture layer.