Abstract:
Laboratory tests on ballast give insight into the behaviour and performance of the ballast layer
under passenger and heavy-haul traffic. It is important, however, to ensure that the simulation
of train loads on the ballast layer in the laboratory represents in-situ loading conditions.
Furthermore, the provision of ballast lateral confinement during laboratory tests should
model the confinement along the track. With adequate, representative loading patterns and
boundary conditions executed during laboratory tests on ballast, the overall response and
performance of the ballast layer can be estimated and predicted more accurately. This gives
an indication of an ideal response of the ballast layer in the field, as well as its impact on track
structure deterioration.
The objective of this study was to develop suitable cyclic loading and boundary conditions
for ballast box tests in the laboratory to represent similar conditions in the field. By conducting
box tests, the ballast deformation results revealed the suitable loading pattern that produced
a similar rate of ballast strain accumulation as the Field Loading (FL) pattern. Furthermore,
boundary condition results showed that decreasing the Level of Lateral Confinement (LoLC)
increased the permanent deformation of the ballast layer and the breakage of ballast. The
laboratory loading pattern developed in this research, as well as comparable laboratory and
field boundary conditions, could provide accurate predictions of the long-term behaviour of
ballast and support the planning for subsequent ballast maintenance interventions based on
realistic and accurate laboratory test results.
