Effect of softening of cement asphalt mortar on vehicle operation safety and track dynamics

Cement asphalt mortar (CAM) softening is a common phenomenon that results from ageing and rain soaking when a high-speed railway is in service. CAM softening seriously affects vehicle operation safety and track dynamics. In this paper, a 3D coupling dynamic model of a vehicle and a China railway track system I (CRTS-I) slab track is developed. By using the proposed model, the wheel-rail contact forces, derailment coefficient, wheelset loading reduction ratio, and the track displacements are calculated to study the influences of CAM softening on the dynamic characteristics of a vehicle-track system. A track-subgrade finite difference model is developed to study the effect of CAM softening on track damage. The results show that track interface shear failure develops when the CAM softening coefficients reach 10-100. The CAM softening coefficient should not be less than 1000, otherwise a high-speed running vehicle may risk derailment.