Test Data Evaluation from Field Measurements of Sleeper Ballast Interface
During the last decades, high-speed railways have become one of the most advanced and fast developing branches of transport. Cruise velocities of such high-speed trains as French TGV, German ICE, Swedish X-2000, etc. are nowadays in the range of 200–300 km/h and increase continuously. This velocity increase brought a new problem to railway engineering, namely the problem of significant amplification of the train and track vibrations at high train speeds. In this regard better identification for the behavior of rails, sleepers and ballast stone bed under actual loading conditions during train passage is essential. The classical railway track basically consists of a flat framework made up of rails and sleepers which is supported on ballast. The ballast bed rests on a sub-ballast layer which forms the transition layer to the formation. The rails and sleepers are connected by fastenings. Railway sleepers are the main structural elements in the railway track system. As well as pressure distribution and load transfer to the underlying layers, railway sleepers maintain track gauge, guarantee lateral stability of the track and contribute towards providing better track geometry. Train axle loads are transmitted through the rails to the ballast bed and then into the underlying ground. Depending on the train speed, an inertia force can be generated in the whole track including the ballast bed and embankment, as a result of the dynamics of the track–ground system. As the behavior of the material is not exactly the same under all sleepers, and since the loading of the track is irregular, the amount of settlement will differ from one sleeper to another. The research presented here is conducted to provide a better understanding of the load transfer mechanism and pressure distribution changes under sleepers through different train passages. In this report the results of a field investigation on the loading pattern of railway sleepers are studied.