The effect of non-linear soil behavior on mixed traffic railway lines

Railway freight services can be added to lines that have previously only be used for passenger services, with the aim of increasing network capacity. Freight trains have larger axle loads and thus can have a negative effect on track longevity, particularly on ballasted lines supported by sub-optimal ground conditions. This is because larger subgrade strains are generated, which can result in non-linear behavior. Therefore it is important to be able to determine the effect of the new rolling stock on track behavior before operation. This is challenging to do because non-linear soil behavior is challenging to simulate. As a solution, this paper presents an equivalent non-linear, thin layer element soil model, coupled to an analytical track model. It is capable of quickly and accurately computing the response of non-linear track behavior. The model is used to investigate the effect of introducing freight wagons on an existing ballasted passenger line with poor ground conditions.