Rail tracks are conventionally built on compacted ballast and structural fill
embankments overlying the natural subsoil. Ballast plays an important role in
providing track stiffness to support heavy traffic loads, and providing rapid drainage.
However, ballast deforms and degrades progressively under the heavy cyclic loading
of passenger and freight trains, which may lead to a loss of track geometry, and
require costly regular maintenance. In particular, track construction requires
appropriate stabilization techniques for ballast, the extent of which depends also on
the type of subgrade.
Comprehensive field trials were carried out on two rail lines in Bulli and recently
in Singleton, New South Wales, Australia. In these studies, several track sections
were reinforced with different types of geosynthetics placed beneath the ballast
embankment. Both fresh and recycled ballast was examined for varying subgrade
conditions. Recoverable and irrecoverable deformations of the substructure were
routinely monitored. It was found that geogrids and geocomposites can decrease the
vertical strains of the ballast layer, resulting in reduced maintenance costs. This
paper describes the comprehensive field instrumentation, construction procedures,
and field performance evaluation of these full-scale geosynthetic- stabilized ballast
embankments in Bulli and Singleton.