Direct shear behavior of gravel-granulated tyre rubber mixtures
The objective of the work presented in this paper is to investigate the direct shear strength of gravel and granulated tyre rubber (GTR) mixtures for possible use as seismic-isolation foundation systems for low-rise buildings. Specimens of gravel, GTR, and selected mixtures (10%, 20%, 30% and 50% GTR - % by mass) were tested in the direct shear apparatus under three normal stress levels of 25, 50 and 60 kPa. The addition of GTR significantly influenced the shear strength and volumetric response of the mixtures. In particular, it is observed that the mechanical behaviour of the mixtures progressively changed from gravel-like (i.e. strain-softening/dilative) to rubber-like (i.e. strain-hardening/contractive), the transition occurring for GTR content between 20% and 35%. Importantly, although a progressive decay of the peak shear strength with GTR content is observed, the friction angle at failure is found to be equal to or greater than 39 degrees for all mixtures.