Development of a simple 2D model for railway track-bed mechanical behaviour based on field data

Abstract

From a practical point of view, it is important to empirically predict the mechanical behaviour of railway track-bed of multi-layers using simple models. In this study, Field monitoring was performed using several accelerometers installed in different layers along a conventional railway track. The accelerometer signals were recorded during the passages of train at 6 different speeds from 60 to 200km/h. The particle displacements were estimated by integrating the acceleration data. Emphasis was put on the dynamic amplification with speed, the attenuation of vibration over depth and the wave propagation along longitudinal direction in a given layer. The obtained results showed that the measured dynamic amplification with train speed depends on the relationship between the train speed and the surface wave velocity. The amplitude attenuation over depth can be represented by an exponential expression. In addition, it was found that the propagation of vibrations along the longitudinal direction had a sinusoidal shape, exponentially attenuated in distance, similar to the displacements calculated by the Winkler beam model. Based on these three mechanisms identified as well as the field data, a 2D analytical model was developed, allowing the prediction of conventional railway track-bed deflections with the axle loads and train speeds. Comparisons between prediction and measurement showed the relevance of the proposed model.