Wheel slip/Slide and low adhesion caused by fallen leaves

Abstract On the sloping section of a train service line located in mountainous areas, idling and skidding of the wheels caused by leaves that fall on the railhead in autumn often occurs, and this hinders the scheduled operation of the train. Although countermeasures such as spraying sand or ceramic particles onto the contact zone of wheel/rail are adopted, the effect is insufficient in late autumn. For clarifying the mechanism of the decrease in the adhesion between the wheel and the rail based on fallen leaves and acquiring information useful for practical implementation of countermeasures, the authors conducted a vehicle running test with driving and braking operations on a test line to investigate the occurrence of wheel slipping/sliding under various railhead states such as dry/wet leaves and dry/wet black accretion films, as well as the adhesion coefficient between the wheel and the rail when dry/wet black accretion films exist on the railhead. The results clarified that the wheel slipping/sliding was likely to occur under wet conditions, in particular frequently occur while wet black accretion films exist on the railhead, and then a low adhesion coefficient was recognized under the same conditions. Regarding the black accretion film formation process, the authors reproduced by a rail cooling device which can simulate atmospheric temperature in mountain area, and clarified that the tannin contained in the crushed fallen leaves has a reaction with steel comment of rail under wet (condensation, frost, light rain etc.) conditions and then black tannin iron was generated and adhere to the railhead. The countermeasure of wheel slip/slide should be focused on how to prevent the formation of the black accretion films or remove the black accretion films in the future work.