Fundamental study on spontaneous corrugation pattern on dry sand due to moving vehicle

Abstract

On unpaved or snowy icy roads, it is known that corrugation pattern on road surface spontaneously emerges due to the repetition of loading by vehicle, and this phenomenon is named washboard road. Washboard road on snowy icy road causes serious problem on the driving of vehicles because the braking performance deteriorates due to lack of friction between road surface and tires. The authors developed an indoor experimental device to reproduce similar phenomenon in a laboratory. As the first step of the study, we chose fine dry sand as a surface material and we successfully reproduced the corrugation on the track. After scrutinizing the growing process of corrugation, we found that the running velocity of the track and the natural frequency of the oscillator are the most important factors for the growth. However, the frequencies of the corrugation converge to some specific value which is different from the natural frequency of the oscillator. Further, we adopted different road materials such as saturated sand, artificial snow and natural snow. This paper introduces interesting findings on formation process of washboard road.