Effects of maintenance operations on railway track's mechanical behaviour by field load testing

Abstract

Deterioration of track causes variations in different mechanical parameters such as value and distribution of track vertical stiffness, which would change the way track mechanical components behave in service condition or maintenance operations. As a result, studying deterioration effects and that of maintenance operations such as tamping and dynamic stabilisation on the mechanical behaviour of both standard and deteriorated tracks could give a better picture of track condition and effectiveness of maintenance operations. In this paper, by carrying out static and dynamic tests and using 89 measurement sensors, the influence of mechanised maintenance operations on mechanical behaviours (strain, acceleration and displacement of rail and sleeper) of a high-deteriorated track and a low-deteriorated track is investigated. The tests were carried out in three different stages (before tamping, after tamping and after track dynamic stabilisation) under a passing train (a 6-axle locomotive and a 4-axle wagon) with 20-ton axle load. Observations indicate that track deterioration causes non-uniform track stiffness and load distribution along the track, such that rail heel strain time history under train loading changes from maximum tensional pattern under the wheels to maximum compressive pattern between two wheels of a bogie. Tamping and dynamic stabilisation cause a more uniform load distribution, which reduces strain and increases acceleration in rail and sleeper. Effects of these maintenance operations on sleepers are far more than that of rail. Deteriorated track is stiffer than low-deteriorated track; stiffness distribution is less uniform and its rails are subjected to less strain and acceleration.