Impact damage mechanism and mitigation by ballast bonding at railway bridge ends

Accelerated deterioration of railway bridge approaches often induces downtime or restricted railway operation; and importantly causes more frequent maintenance, which is costly and time-consuming. Such deterioration is believed to occur because of high dynamic impact loading from the difference of stiffness between railway track and bridge, and poor condition of track support at the bridge ends. The abrupt change in track stiffness often causes accelerated degradation of track geometry and components and poor ride quality, demanding higher maintenance. On this ground, there are a number of improvement programs that have been implemented in order to provide a transition to smooth the stiffness interface. In principle, the transitions were designed to either:
• Provide a gradual increase in the stiffness of ballasted track to match that of the stiffer track (stiffness ramping); or
• Equalise the stiffness and rail deflection, usually by controlling the resilience of rails on the stiffer track, or by adding more resiliency to the stiffer track.

This paper presents the ballast breakage mechanism at railway bridge ends, together with a field trial and the measured dynamic behaviour of the bridge ends improved by using ballast glue/bond method. This field study demonstrates an application of ballast glue/bond to improve the smoothness of stiffness along the ballasted track at bridge ends. The method appears to be useful for brown-field maintenance where adjacent aged infrastructure exists. The ballast glue/bond could reinforce the ballasted track stiffness through the aggregate adhesion whilst the drainage property of ballast in any existing track is not undermined. The field trail was conducted at a railway bridge in New South Wales, Australia. The results show that the ballast glue/bond suppresses vibrations over broad frequency ranges but excites the track resonances at low frequency range (0-10 Hz). After one year revenue services, the field survey investigation indicates the stability of track geometry at the bridge end systems. A discounted financial gain from the trial is also demonstrated as a case study.