Improving the performance of railway tracks through ballast interventions

Maintenance and eventual renewal of a ballasted track constitute major operational costs for a railway network. Thus, significant benefits would accrue from a more robust track design having a longer service life and reduced maintenance requirements. This paper presents the results from a laboratory study and explores the potential to achieve this through improving the ballast grading and reducing the ballast shoulder slope. Cyclic loading tests were carried out on a section of track representing one sleeper bay in plane strain, in the Southampton Railway Testing Facility. A cyclic load representing a 20 tonne axle load was applied at 3 Hz for at least 3 million cycles, during which measurements of permanent and resilient vertical deflection were made. Certain interventions are found to result in lower rates of permanent settlement and different resilient ranges of movement. Supplementary measurements to determine longitudinal pressure, ballast breakage and attrition, and shoulder slope movement were used to explore the mechanisms responsible for the observed improvements in ballast bed performance. It is concluded that the use of finer ballast gradings and a shallower shoulder slope have the potential to reduce maintenance requirements.