The shapeirregularity of sand grains leads to eccentric distances in grains, and their variant positions when they begin to move results in the diversity of eccentric angle.
沙粒形状的不规则性使得沙粒的质心存在着偏心距，且沙粒所处位置的不同使其偏心角各异。
2
The influence of train running speed, wheel-rail friction coefficient, vehicle load, track geometric irregularity, partly load, gauge and the shape of wheel tread on derailment was emphasized.
The plastic deformation would more easily occur due to the impact contact, but it is independent to the shape of tread. However, to eliminate the irregularity between the wheel and rail is necessary.