Effect of Rubber Inclusion on the Friction Angle at Critical State for Different Host Sands

Abstract

Triaxial shearing tests were conducted on five types of pure sand and the corresponding sand-rubber mixtures, to comprehensively investigate the effect of rubber inclusion on the friction angle at critical state (φ′ _cs) for different host sands. In general, it has been considered that φ′ _cs is mobilised from two aspects: inter-particle friction φ′ _μ and particle rearrangement φ′ _b. In this study, φ′ _μ values at different sand and sand-rubber interfaces were measured by an inter-particle loading apparatus and used to correlate the macro-mechanical response with the micro-scale index. It was found that the φ′ _cs of glass bead/river sand-rubber mixtures increases comparing with pure sands, while the φ′ _cs of completely decomposed granite (CDG)-rubber mixtures decreases comparing with pure CDG. The φ′ _μ shows a similar trend with φ′ _cs that the φ′ _μ at glass beads/river sand-rubber interfaces increases notably in comparison to pure sand contacts but there is an obvious drop from CDG to CDG-rubber interfaces. The φ′ _b shows an opposite trend that the φ′ _b decreases in glass beads/river sand-rubber mixtures since the reducing sand-sand contacts will weaken the effect of interlocking, whilst the inclusion of rubber prevents the breakage of CDG particles therefore leads stronger interlocking effect, i.e. φ′ _b increases. Interestingly, when adding rubber particle into 50% river sand-50% CDG mixtures, all those factors are balanced therefore the φ′ _cs values before and after adding the rubber particle keep constant.