DEPTH OF BALLAST, BALLAST POCKETS, BALLAST FOULING, REMEDIATION
BBRI-Zetica carried out a rail radar scan between mileposts MP575 and MP576 to image ballast, sub-ballast and top of formation to identify irregularities which may identify the causes of a track geometry (cross level) exception. This exception had resulted in a slow order extending between MP575.068 and MP575.754.
The location of the significant track geometry left/right surface exception (arrowed above) at approximately MP575.488 is characterised by a well-defined ballast pocket that extends across the width of the trackbed and to a modelled depth of 36 – 40 inches below top of tie. In order to remediate the existing problem it was recommended that the trackbed be re-engineered (formation treatment / re-ballasting) between MP575.450 and MP575.550 (length of 528ft) to a minimum depth of 40”. The use of a geotextile liner and sand protection blanket was recommended to improve trackbed stiffness and drainage over this section.