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PANDROL Under Tie Pads

Under Tie Pads are tailor-made resilient systems designed to reduce track maintenance, increase the quality of the track and provide vibration mitigation by fixing elastic elements to the bottom surface of the ties.

Pandrol UTP’s are designed to be bonded into the wet concrete sleeper during manufacture, by using the patented CDM MFF® technology (Micro Filament Fastener).  The CDM MFF® is suitable for use with any type of sleeper making process (long line or carrousel) and concrete type.

Product features by product sector

  • Lifecycle Cost Reduction
  • Transition Zones
  • Ballast Contamination
  • Noise and Vibration Control
  • By using Pandrol CDM Track Under Tie Pads, an improved load distribution and a reduction in the pressure on the ballast and superstructure will be obtained. This is the result coming from:

    • An increased contact surface between tie and ballast: contact surface can be increased up to 35% using the appropriate Under Tie Pad, compared to 5-10% on a non-padded tie.
    • An increased number of ties supporting the axle load: the elastic line of the rails increases by the introduction of a resilient element, distributing the axle load over a greater number of ties.
    • A direct reduction of the dynamic loading from the ties into the ballast

    USP Track Quality

  • Main advantages by using Pandrol CDM Track Under Tie Pads:

    • Increased longevity of the track and all the components

    • Reduction of rail corrugation, especially in tight radius curves = extending the grinding interval by at least a factor 2

    • Possibility of reducing the ballast bed thickness (up to 10cm)

    • Minimising maintenance efforts: Levelling, Lining and Tamping (LLT) period extended by a minimum factor of 2

    • Payback period is approximately 3-4 years

  • Transition zones are sections along the track where the track superstructure changes on a relatively short distance – such as bridge approaches, approaches from ballasted track to slabtrack, switches and crossings, etc… typically areas that are difficult to maintain. The change in track superstructure results in a change of the track stiffness, which generates larger stresses in the track components during train passage and therefore will result in higher maintenance cost.  That’s where elastic elements such as Pandrol CDM Track Under Tie Pads can significantly reduce the loading in the track and protect the track component to consequently keep your maintenance costs under control. In transition zones, two main issues can be noted:

    • Differential track settlement, due the different track structures and leading to increasing forces on the track components as the number of train passages increases. Track components, such as tie and ballast, will start to wear down (eg.hanging ties), which will increase even more the impact forces.

    Pandrol CDM Track Under Tie Pads help to distribute the loading more evenly in the track, which has a positive influence on the track settlement, reducing the impact loadings and consequently increasing the lifecycle of the track

    • Differential track stiffness, resulting in a differential rail deflection, and thus leading to increased dynamic rail-wheel forces in the track structure.

    Pandrol CDM Track Under Tie Pads are designed to minimize the deflection differences by using its Track Elastic Model.  This Track Elastic Model allows Pandrol CDM Track to calculate the deflections in function of the project specific track parameters and as such define the most suitable under tie pad.

  • Ballast fouling by subgrade pumping, coal and iron ore spilling is understood as major cause of track deterioration in many countries over the world. As contamination clog the ballast voids, the subsequent stiffness degradation results in reductions in track performance and lead to major maintenance costs.

    Pandrol CDM Track Under Tie Pads help to distribute the loading more evenly in the track, which has a positive influence on the track settlement, reducing the impact loadings and consequently increasing the lifecycle of the track

    In desert areas one of the most important issues is ballast layer solidification due to windy sand accumulation. This phenomenon increases track modulus which leads to serious damage in railway track components. In addition, since the contamination of the ballast is random, areas with high contamination will alternate with areas with lower contamination, resulting in differential track stiffness, comparable to transition zones.

    Pandrol CDM Track Under Tie Pads help to keep the overall track stiffness at a lower level, regardless of the presence of sand in the ballast, resulting in higher track quality and less maintenance costs.  In addition, when selecting the suitable stiffness of the Under Tie Pad, the differential deflections along the track can be kept under control and as such reduce the dynamic rail-wheel forces.

  • Noise and Vibration control is achieved thanks to the insertion of an elastic layer between the rigid concrete tie and the ballast. The level of vibrations reduction will depend on the stiffness of the material introduced

    • Alternative to Under Ballast Mats (UBM): Soft UTPs may be a good substitute for UBM if the requirement is to control vibrations in the frequency range above 40-50 Hz
    • Ground-borne noise control: it has been demonstrated that up to 10 dBv reduction in vibrations within the frequency band of maximum energy can be achieved
    • Air-borne noise control: Although not the main objective, the possibility exists for reducing train passage noise in curves indirectly, due to the improvement in the quality of the track

    Pandrol CDM Track has a full range of Under Tie Pads, each with different stiffness characteristics and Noise & Vibration isolation performance.  The specific type of  Under Tie Pad for your project is selected using our Track Elastic Model, which allows us to calculate the isolation performance  in function of the project specific track parameters and boundary conditions and as such define the most cost-effective under tie pad to meet your requirement.