Sand-tyre chip (STCh) mixtures can be used in many geotechnical applications as alternative backfill material. The reuse of scrap tyres in STCh mixtures can effectively address growing environmental concerns and, at the same time, provide solutions to geotechnical problems associated with low soil shear strength and high dilatancy. In this paper, the shear strength and dilatancy behaviour of STCh mixtures have been investigated. A series of monotonic triaxial tests has been carried out on sand mixed with various proportions of tyre chips. It has been found that tyre chips significantly influence the shear strength and the dilatancy behaviour of STCh mixtures. The effects of confinement and relative density on the shear strength, dilatancy and initial tangent modulus of the STCh mixtures have also been investigated. Moreover, a dilatancy model for STCh mixtures has been proposed and validated with the experimental results.