Determination of the characteristics of local instabilities, taking intoaccount their causes and loads

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The purpose of subproject EPIB 1.1, entitled Determination of the characteristics of local instabilities, taking into account their causes and loads, is to determine the causes of locale instabilities on existing conventional ballast tracks. The characteristics of local instabilities will be determined by evaluating the data measured on selected track-sections; primarily the amplitude and wavelength resulting from the relative displacement of the track subjected to traffic loads in the vertical direction. The knowledge generated will be used for the analytical calculation of the traffic load, (quasi static and dynamic forces), which results from a local instability and that affects the existing track. The main goal is the early detection of local instabilities by evaluating the axle bearing acceleration. Through in-situ measurements (EPIB 2) on a track bed in equilibrium and for arising local instabilities, first a typical pattern for local instabilities will be developed based on wheel-rail forces. The axle bearing acceleration will also be determined by the same wheel-rail forces. Finally, an algorithm based on the characteristic of local instabilities will be developed. With this algorithm local instabilities can be detected systematically and at an early stage by axle bearing acceleration. Taking into consideration the knowledge acquired in subproject EPIB 1.1, the goal of the collaborative project includes the determination of the causes of local instabilities as well as the determination of a rough prognosis of the further process of track quality deterioration in consideration of an existing operating program. Subproject EPIB 1.1 is part of the main project known as Early detection of local instabilities on existing track beds for conventional ballast tracks by fine-grained soils in substructure/subsoil. The results obtained from subproject EPIB 1.1 serve as the basis for the development of two more sub-projects EPIB 1.2 and 2 EPIB. Moreover, EPIB 1.1 contributes to the overall objective of the joint project by achieving the main objective, which is the early non-destructive detection of local instabilities using axle bearing acceleration.