Effect of Different Rainfall Intensities on Wheel-Rail Adhesion Characteristics under Large Slip Ratio Conditions

When the slip ratio reached 24%, due to the rupture of the water film, the adhesion coefficient sharply rose to the dry state level (approximately 0.4). Under moderate and heavy rain conditions, with the increase in slip ratio, due to the combined effect of the rough wheel-rail contact surface and higher relative sliding speed, a double-peak in the wheel-rail adhesion coefficient was observed. Under torrential and extreme torrential rain conditions, due to the thicker water film at the wheel-rail interface, the adhesion coefficient showed a typical trend of initially increasing then decreasing as the slip ratio increased.

In the unloading stage (slip ratio from 30% to 0%), under all rainfall intensities, with the decrease in slip ratio, the adhesion coefficient initially increased, then decreased. Furthermore, with the increase in rainfall amount, the adhesion coefficient decreased. Therefore, under light and heavy rain conditions, the slip ratio should be controlled within the range of 5% to 12.5% to improve the adhesion coefficient.

Once the adhesion coefficient is recovered to the dry state level, the slip ratio should be decreased promptly to avoid severe wheel-rail damage. However, under torrential and extreme torrential rain conditions, if the adhesion coefficient decreases significantly, the method of sanding should be applied to improve the adhesion coefficient to ensure train operation safety.