Keywords: mud hole, detection, management, dynamic loads, numerical simulation, track bed quality.

Track bed stability is of major importance for the safety and comfort of rail traffic. Quasi-static and dynamic loads from train-traffic are applied to the entire track system: superstructure, substructure and subsoil. Owing to the dynamic loads on the track system and lack of maintenance of the track bed, an accumulation of excess pore water pressure can develop within the substructure. Furthermore, a pumping effect exerted on the track system, which depends on the axle load and velocity of the vehicle, may cause mud hole formation, rising of the underlying soil, ballast contamination and the clogging of gravel bed pores. Consequently, the subgrade resistance is reduced and hence the system loading capacity. The main objective is to detect mud holes, as early as possible, by non-invasive, non-destructive measurements to avoid costly interim or long term treatment. In this paper a structured overview will be provided about existing guidelines for mud hole detection and modeling techniques employed in track-substructure problems.

The paper focuses on a comparison of certain modeling parameters due to the moving train load. As a result of the high velocity, vibration speeds and vibration acceleration on the track system, elastic and plastic deformations might develop in the vicinity of the track-subgrade system especially in case of ballast breaks on soft cohesive soils. Two models simulating a moving train have been proposed and compared. Based on the results of further simulations, a proposal for an improved mud hole management will be provided in future.

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