Stone blowing as a remedial measure to mitigate differential movement problems at railroad bridge approaches

Railroad track transitions such as bridge approaches often experience recurrent track geometry problems due to differential settlement between the bridge and the adjacent track. The resulting “bump at the end of the bridge” leads to significant passenger discomfort and causes rapid deterioration of the track as well as vehicular components. In general, railroad managers address recurrent track geometry defects through track resurfacing methods, such as tamping that involve raising the track through mechanically induced vibration and rearrangement of particles within the ballast layer. Although widely used for track resurfacing, the tamping process tends to destabilize the ballast layer, and the track may rapidly return to its former deteriorated state based on the traffic flow. The method of “stone blowing,” on the other hand, which was developed as an alternative to tamping, relies on the principle of injecting fresh ballast particles into gaps underneath ties and raising the track level rather than disturbing the packing condition of the existing ballast. In a recently completed research study in the United States, stone blowing was successfully implemented as a remedial measure to mitigate the problem of differential movement at a problematic bridge approach along Amtrak’s Northeast Corridor. Advanced geotechnical instrumentation was used to monitor transient deformations within individual track substructure layers before and after stone blowing. Moreover, tie support conditions and track geometry data were also analyzed to quantify the effectiveness of stone blowing on the improvement of track performance.