Immediately after laying a new track and following tamping work or ballast bed cleaning, not all ballast stones are lying in a consolidated and therefore ideal stable position. Up to 1973, trains could travel over such tracks for certain periods of time only at reduced speed.
Plasser & Theurer developed dynamic track stabilisation to avoid these temporary speed restrictions as well as any irregular settlements. Stabilising units form the heart of this technology.
After construction jobs on the track such as maintenance, ballast bed cleaning or new track laying, some of the ballast stones are not in an ideal position to each other. Very often the ballast stones only touch at the points and edges. This means there is a lack of density and stability which is necessary to anchor the track in the ballast ideally.
Originally, the ballast bed settled over time under the train loads. But temporary speed restrictions had to be imposed while these initial settlements took place. Above all, this did not achieve the initial quality of the track and the long durability that is possible nowadays. This changed with the advent of dynamic track stabilisation.
The stabilising units are friction-locked to both rails via rollers. Flywheel gears produce a horizontal vibration acting crosswise to the track. This is transmitted to the ballast bed achieving a virtually force-free re-arrangement of the ballast stones to produce a denser structure. The resulting settlement of the track is controlled with the help of the levelling system. Dynamic track stabilisation anticipates the unavoidable initial settlements deliberately and in a controlled way. This increases the quality reserve of the track and produces a more durable track geometry. At the same time it raises the track’s resistance to lateral displacement.