Simulations of Segregation and Ripples on Unpaved Roads

In this work we present a study on the ripples formation in unpaved roads. This effect, also known as washboard road, annoys thousands of people around the world and it does not exist yet a closed theory about it. This study is made with Molecular Dynamics Simulation applied in soft grains in two dimensions. In this model, the grains are 2d disks with motion of translation and rotation and under action of a constant gravitational field. The simulations are performed in a box with horizontally periodic boundaries. The force of contact has a radial component, also called spring dashpot model, and a tangential component, which charges the friction between the grains. Simulating a rolling wheel, a large grain rolls over the other small disks. In the simulations we observed that the ripples can arise or not together with the segregation of the grains, but recent articles showed that this phenomenon is not determinative to the formation of the corrugations, although they are observed in the real roads. We investigate the evolution of the ripples through of fast Fourier transform (FFT) and we analyzed the segregation by radial distribution function (RDF). We also verified some cases by changing the basic model parameters: physical quantities and geometric elements which play some role in this problem.

Acknowledgment: UFOP, CNPQ, CAPES and FAPEMIG