Prediction of RCF Damage on Underground Metro Lines

London Underground (LUL) is one of the largest metro networks in the world and carried nearly 1.5 billion passengers in 2015. This increasing passenger demand leads to higher axle loads and shorter headways in the railway operations. However, this has a detrimental impact on the damage generated at the wheel-rail interface. In spite of the advances in rolling stock and track engineering, new developments in material manufacturing methods and rail inspection technology, cracking in rails still remains a major concern for infrastructure managers in terms of safety and maintenance costs. In this study, field data from two metro lines on the LUL network was analysed to identify the distribution and severity of the different damage types. Detailed vehicle dynamics route simulations were conducted for the lines and the calculated wheel-rail forces were investigated to assess the applicability current models for the prediction of rail damage on metro lines. These models include the Whole Life Rail Model (WLRM), previously developed for Great Britain (GB) main line tracks, and Shakedown theory. The influence of key factors such as curve radius, different friction conditions, track irregularities and wheel-rail profiles on the wheel-rail contact interface have been evaluated and compared with outputs from simulations on mainline routes. The study found that the contact patch energy (Tγ) and the interaction between wear and RCF in rails were highly influenced by the characteristics of metro tracks. It was also shown that both the Tγ and Shakedown methods can provide successful prediction of damage susceptibility of rails. However, in order to increase the accuracy of damage predictions and to ascertain the severity of different damage types, the duty conditions which are observed by the rail and the changes in contact conditions resulting from the successive vehicle passes should be considered in the modelling.