In ABAQUS software, the gravel road can be simulated by using the properties of gravel. The main properties which includes Young's modulus, unit weight, Poisson's ratio, angle of internal friction and dilation angles. Further, the material behaviour is simulated by using various failure constitutive models like Mohr-Coulomb and Drucker Prager models. I also recommend you to refer ABAQUS manual for further details about the model..ok all the best..