Monitoring of transition zones in railways

Transitions between railway track on embankments or natural ground and fixed structures such as bridges and culverts often require substantial additional maintenance to preserve line, level and ride quality. This extra maintenance not only increases costs but also causes delays. Despite its importance for railway infrastructure owners, the fundamental cause of the poor performance of transition zones is not fully understood. To gain a better insight into the physical mechanisms involved, an extensive field investigation has commenced on a transition zone in The Netherlands. The transition zone consists of two reinforced concrete slabs which span between the normal track and a concrete culvert – a form of structure common on Dutch Railways. At the study location, the track is generally on a 4 m high embankment, initially built of sand, on top of a peat/clay layer 7 m thick. At a depth of 11 m below the track there is a natural sand layer, in which the piles that support the culvert are founded. The transition zone requires substantial additional maintenance. This paper presents data on the dynamic behaviour of the transition zone in response to scheduled passenger trains. Accelerations and velocities of the track, soil and approach slabs were measured, from which displacements were calculated. The dynamic track stiffness and the motion of the embankment and approach slab are also discussed