Analysis of Dynamic Behavior for Slab Track of High-Speed Railway Based on Vehicle and Track Elements

Abstract

Slab tracks are used worldwide in high-speed railways. The slab may be cast in situ, resulting in a continuous length of concrete, or it may be constructed in discrete precast sections laid end to end. According to structural characteristics of the China Railway Track System (CRTSII) slab track system, a model for dynamic analysis of vehicle-track-subgrade coupling system has been developed. Based on the model, a new type of slab track element is presented, and the associated stiffness matrix, mass matrix and damping matrix for the element are deduced. This element includes rail, rail fastening and pad, prefab slab, cement-asphalt mortar, hydraulically bonded layer, and subgrade. By means of the Lagrange equation, a numerical method for coupling the moving wheel and the rail with explicit formula is presented and the associated finite-element equation is formulated. As application examples, parameter studies on the track vibration of the slab track structure, such as stiffnesses and dampings resulting from the rail pad, CA mortar (cement-asphalt mortar) and subgrade, are investigated. To understand dynamic behavior of track transition from conventional ballast track to slab track, the effects of train speed and track stiffness on track vibration in the transition are evaluated. The obtained results show (1) reasonably chosen parameter values of the slab track structure and suitably specified stiffness of the transition will significantly improve the behavior of the track performance; (2) changing track stiffness in transition has an influence which increases with an increase of railspeed, on the vertical rail acceleration and the wheel/rail contact force; (3) smoothing of track stiffness in transition can reduce track vibration and improve the operational quality of the train. Countermeasures include long ties, additional rails, hot mix asphalt (HMA) underlayment, slab track approach, stone columns and piles to strengthen weak subgrade, rail seat pads, rubber tie mats, and other countermeasures.