Effect of Rubber Inclusion on the Friction Angle at Critical State for Different Host Sands
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.
KeywordsSand-rubber mixture Critical state Inter-particle friction Interlocking Particle breakage
This study was supported by the Environment and Conservation Fund (ECF) under the project ‘Recycling tyre waste as a useful geo-material to enhance sustainability’ (Project number 55/2016). The authors acknowledge the grant 7200533 (ACE) funded by City University of Hong Kong.
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