XiTRACK™ Projects:  WCML Bridge Resonance Programme

XiTRACK Polymer was applied to ballast on a series of bridges on the West Coast Main Line in Network Rail’s Test Site A, in the Trent Valley and in Scotland in a programme starting in 2001.

The bridges in the series were usually based on a steel plate decking and had been found to be subject to pre-resonance problems at normal passenger train speed.  They had been shown to be susceptible to ballast movement due to induced excitement with consequent loss of track alignment.  This problem had been demonstrated to be likely to get worse with Pendolino increased line speeds.  Under prevailing traffic, frequent re-alignment of the track and ballast repair was necessary and imposed speed restrictions were common. 

A design and specification using XiTRACK Polymer was drawn up with Mott Macdonald and Railtrack’s WCML Upgrade Team.  The solution was intended to be short-term before the bridges were replaced in a planned future programme.  All treatments have exceeded their planned operating life, some by 100%.  A number have now been replaced as part of the upgrade programme, none has needed any ballast attention since application.  The bridges performed as expected during high-speed Pendolino trials.

Alternative conventional ballast treatments had been discarded because they were considered ineffective.

Part of the specification developed was that, even though it was the source of the problem, the dynamic performance of the bridges could not be altered; it has been demonstrated subsequently that this requirement has been met.  Ballast porosity was not affected.