Abstract:
With past embankment failures on the heavy haul coal export railway line between Ermelo and
Richards Bay in South Africa, a study was conducted focusing on the modelling of embankments
in a geotechnical centrifuge. This was done in order to investigate the influence of static and
cyclic loading on settlement, and to evaluate the potential failure of the embankment under the
loading conditions. The effect that moisture has on the slope stability was also investigated. A
suitable loading system was developed that could be used to apply static and cyclic loading to a
model embankment in the centrifuge. Embankment models representing a standard slope and
using one material type with varying moisture content were built and tested in the centrifuge.
Clayey sand material was sampled from one of the sites where a failure occurred on the coal
line and was used for the tests. The loading system simulated the loading created by a heavy
haul coal train with a 26 t per axle load along the length of an embankment. The results from
the tests conducted in the geotechnical centrifuge indicated that settlement resulting from
the cyclic loading was on average 67% higher than that of the static loading when considering
loaded time. It was observed that the tests with increased moisture content exhibited
significantly reduced stability. A completely developed slip surface failure was not observed.
However, cracks formed at the crest of the embankment along its length, which indicated a
downward shift of material. The research therefore concluded that cyclic loading on railway
embankments increases permanent vertical settlement of the embankment compared to static
loading. As the moisture content was increased for the different tests, there was a clear increase
in crack development at the crest of the embankment along its length.
