Deflectometer-based analysis of ballasted railway tracks

The falling weight deflectometer (FWD) device is used in the UK for the dynamic testing of ballasted railway track. Using the deflection data obtained from the test, elastic modulus values of the track substructure required to build a numerical model of the track can be determined using a procedure known as back-analysis. The numerical model so calibrated can be used to determine the effect of the traffic loads on the stresses, strains and deformations in the railway track system, and is an important component of an analytical approach to track substructure design. In this paper, the use of dynamic finite-element analysis to back-analyse the material properties of the railway substructure from FWD deflection data has been demonstrated by means of an example. The numerical approach presented is the rational method for FWD-based inverse analysis and condition evaluation of ballasted railway tracks, and becomes practicable owing to continued advances in finite-element and computer technologies.