Dynamic stabilisation of the tracks is a successful method developed by Plasser & Theurer for the optimum conservation of the track geometry. There is scarcely another method in the track laying and track maintenance sector that has been investigated by railways and research institutes as intensively as dynamic track stabilisation. The findings from these wide-ranging tests have contributed towards further optimisation of the technique. Today the dynamic track stabilizer is an established feature of the machine fleets of railways and contracting firms all over the world.

The aim of dynamic track stabilisation is to achieve an improved anchoring of the track skeleton in the ballast bed. After dynamic stabilisation, the condition of the track offers greater operating safety and enables travel at the maximum line speed, particularly on newly laid track or after full track maintenance. This helps to avoid speed restrictions and reduce operational hindrances overall.

Moreover, the track should be available for a longer period in its geometrically correct position or within the tolerance range. The influence of the dynamic track stabilizer on the track results in a considerably longer durability of the track geometry, a fact which has been documented extensively, and this brings additional quality reserves into the track.

Systematic application of this method of track maintenance brings a good rate of return on investment for the entire track maintenance by extending the intervals between maintenance operations and also brings savings in the operating sector by dispensing with speed restrictions.

The dynamic track stabilizer sets the track in horizontal oscillations whilst applying a static vertical load at the same time. This causes the ballast stones to re-arrange their position, with the result that the track is lowered and "rubbed" into the ballast bed. The vibration transmitted to the ballast lies in the natural frequency range of the ballast and causes the ballast stones to settle closer together in their cavities. The result is a dynamic re-arrangement of the ballast stones. The number of cavities is reduced, instead of individual contact points the ballast stones have a larger number of contact surfaces and contact edges. Between sleepers and ballast stones too, the sum of contact surfaces rises considerably. The vertical static load serves basically to transmit the oscillating movement and to regulate the controlled settlement.

When maintenance is performed using a tamping machine, the track is levelled, lifted, lined and tamped. The tamping machine consolidates the ballast underneath the sleepers in the area of the tamping zones. The subsequent dynamic stabilisation produces a homogeneous ballast structure.

This homogenisation of the ballast bed raises the durability of the track maintenance. The overall larger frictional surface between sleepers and ballast produces a larger resistance to lateral displacement both for the loaded as well as for the unloaded track. In contrast to other conventional methods of ballast treatment there is a spatial consolidation with a completely altered ballast structure.

A new bearing support is produced for the sleeper, while retaining or even improving the perfect track geometry, wider areas of the ballast bed take over the transmission of the forces. The resistance to longitudinal displacement is raised too.

The track's resistance to lateral displacement (RLD) provides fast information about the safety standard of the track.

The measurement of the RLD during operation of the dynamic track stabilizer was derived mathematically from the known and measurable parameters and adapted for measuring technology by the Plasser & Theurer research and testing department. The basis for the establishment of the resistance to lateral displacement is the fact that its value is proportional to the energy consumed by the vibrating units (friction work). The track's resistance to lateral displacement is calculated from the constant amplitude, the constantly set frequency and the variable working pressure of the hydraulic motor and can be measured and recorded as an absolute value (kN) and as a percentage value in comparison to the state before the work.

By measuring and recording the resistance to lateral displacement directly during the last working pass performed on the track, the dynamic track stabilizer provides an ideal option to evaluate the parameters for the track's safety against buckling.

This method of work is mainly used on new track laying, track relaying and in the course of ballast cleaning. For optimum homogenisation, the ballast bed is tamped and dynamically stabilised layer by layer.

The first tamping pass is made after placement of the first layer of ballast: the track is lifted and tamped. This is followed by the dynamic track stabilizer operating without levelling measuring device, that is to say, the stabilizer works with a constant basic setting and thus produces optimum homogenisation. The settlements achieved may be uneven in some cases, but the compactness of the ballast bed is outstanding. A varying number of ballast placements and machine passes are required, depending on the thickness of the ballast bed.

At the last tamping pass the track is put into the correct final position and then the dynamic track stabilizer is applied, using the levelling system. The result is an exactly positioned track in a homogenised ballast bed which can be re-opened for maximum line speed immediately after treatment.

The purpose of every track maintenance must be to place the track in the geometrically correct position and to conserve this state for the longest possible period.
To minimise irregular settlements caused by the train load following maintenance with the tamping machines, these initial settlements are anticipated in a controlled way by dynamic stabilisation. The settlements are performed by the dynamic track stabilizer with the help of a measuring reference system. A settlement value is pre-selected and the pressure in the loading cylinders is controlled by the levelling system. This means that after stabilisation the track geometry is as accurate as after the operation of a levelling, lining and tamping machine and remains so over a longer period.

The track is then immediately available for traffic at the respective maximum speed

Homogeneous, spatial consolidation of the entire ballast bed

Increase of the resistance to lateral displacement

Careful treatment of the ballast material by dynamic re-arrangement of the ballast stones to avoid fines

The danger of track buckling is reduced

Durability of the accurate track geometry over a longer period, raising the quality reserve of the track

The intervals between maintenance are extended

Great savings in the sectors track maintenance and operational hindrance costs when the technique is applied regularly

Dynamic stabilisation raises the safety and helps to lower costs