Improvement of rail creep data to measure the stress state of a tangent continuously welded rail (CWR) track

Monitoring the longitudinal rail movement or rail creep is regarded as one of the effective ways to understand the rail-stress states in critical locations such as fixed structures (level crossings,turnouts and fixed top bridges), in sags at the bottom of gradients or any track segment with a history of buckles. However, rail stress can be changed due to thermal and mechanical loads in both longitudinal and vertical directions. Many railway companies use a fixed schedule to assess rail creep, particularly in critical locations. This may not be adequate to reduce the risk of summerbuckling and winter pull-apart problems. Current practice of creep measurement does not consider the effect of rail temperature, the vertical movement of track, inherent inaccuracy of the measurement system and any non-uniformity in track structures. In a field test, Total Station Survey equipment has been used to monitor the changes inlongitudinal and vertical displacements of the rail at points on a tangent track section in the heavy haul Blackwater system of the QR National network at Edungalba. This 26 tonne axle load track section with 1% gradient and 60 kg/m rail was instrumented with strain gauges, thermocouples and rail stress modules. The creep in this section has been quantified in terms of rail strain and rail stress with respect to the rail temperature. In this paper, a method is proposed considering the longitudinal creep data, vertical displacement of the rail and rail temperature to accurately predict the stress state of a tangent rail track.