Planar sliding is a typical failure mode of dip slops, in which an unstable rock block slides along a weak plane, resulting in a rapid movement. Based on the previous studies, the friction coefficient of the sliding plane varies with the velocity. To reflect the velocity-dependent friction behavior, this study proposes a particulate interface model (PIM) of the particulate DEM to simulate the planar sliding behavior. To validate the performance of the proposed model, the results of a DEM simulation of the planar sliding of a rigid block are compared with the analytical dynamic solution. The results reveal that the PIM simulation is consistent with the analytical dynamic solution with or without consideration of the velocity-dependent friction law. The ordinary contact model does not accurately reflect the theoretical dynamics owing to the high resistance. With respect to the deposition distribution, the different interface models yielded the various velocities before impact, and therefore various failure patterns of the block and appearances of the deposition. The block velocity significantly influences the number of cracks. The results of the analysis reveal that the PIM can capture the planar sliding and deposition behavior of dip slope failure.