In modern track systems, sleepers are soled to reduce the demands placed on the ballast while at the same time lowering the track costs.
What are sleeper soles?
Designated as a sleeper sole is an elastic layer on the bottom of a railway sleeper. This layer may be applied in the course of the manufacturing process for the sleeper (placing of the layer on to the unset concrete) or subsequently by gluing the layer to the bottom of the sleeper.
Improved bed qualities through plastic soling
In certain technical parameters concrete sleepers cannot match the properties of wood sleepers. With an elastic plastic layer on the bottom of each sleeper, however, the bed qualities of a wood sleeper are achieved in respect of the contact surface between sleeper and ballast.
Stability and long-term durability
Increasing hand in hand with the increasing speed and operational loading in railway traffic are the demands placed on the ballast of a permanent way. In order to master the resulting increased loadings, Paul Müller engineers have developed a sleeper sole that satisfies all the relevant requirements.
The sleeper sole is firmly bonded to the soffit of each concrete sleeper. It relieves the loadings on the ballast, increases the stability of the track bed and improves the dynamic and acoustic properties of the permanent way.
The facts in brief
- Reduction of maintenance work on track systems
- Amortisation of the cost of soling within 2 to 3 years
- Increasing of passenger comfort
- Long-term durability (fatigue resistance) of the soles > 35 years
- Recyclability of the soles = 100% to German Closed Substance Cycle Waste Management Act
Mode of functioning
Through the selection of a sole material with properties meeting the particular demands, the elastic and plastic deformation behaviour of the soles is matched to each customer's particular conditions of use.
1. Plastic deformation component of the sole
Through the tips of pieces of ballast being pressed into the sole, the plastic deformation of the latter ensures positive locking up to an equilibrium of forces and in this way protects the ballast and increases the resistance to lateral displacement through the geometric matching between ballast and sole.
Photogrammetric evaluations following long-term tests have confirmed a contact surface of approx. 23 % on the example. The contact surface between ballast and sleepers without soling is assumed to lie between 5 and 8 %.
- Reduction of the contact pressure per unit area between sleeper and ballast by approx. 250 %
- Reduction of the settling of the track by a factor of 4 relative to unsoled sleepers
- Reduction of maintenance costs by a factor of 2 to 3
- Reduction of the rate of deterioration of the position and levelness of a track by a factor of 3 to 4
2. Elastic deformation component of the sole
In every phase of the time-related pressing of tips of pieces of ballast into the soling the sleeper sole acts in a constant "elastic" and load-distributing manner. The amplitude does not depend on the degree of plastic imprinting but is solely a function of the composition of the material, the thickness of the sole and the dynamic loading from the rail traffic. The elastic deformation component is defined by the ballast module and is characterized in addition by the relationship between the static and dynamic components of the latter. We will be pleased to send you on request technical data on these criteria "customized" to your conditions of loading.
- Under conditions with our sleeper soling, the oscillation amplitude of the ballast beneath the sleeper is reduced from 0.4 mm to 0.1 mm.
- Passenger comfort is increased and noise emissions reduced.
- The formation of grooves and other damage to the rails is prevented to a very large degree.
- Dynamic stiffening < 1.5
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