We present a SPH numerical model to simulate rapid, free-surface flows of dry granular material. SPH (Smooth Particle Hydrodynamics) is a meshless numerical approach based on a Lagrangian description of continuum fluid mechanics equations, using a particulate discretization of the simulated domain. This method is well adapted, in particular, to simulate free-surface flows of complex fluids in complex geometries. The formalism requires considering fluids as slightly compressible, pressure being evaluated from density variations. The rheology of flowing dry granular materials is implemented using the 3D constitutive law recently proposed by Jop et al. (Nature, 2006), which considers granular materials as pressure-sensitive, viscoplastic fluids.