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RK4 - Trackbed Geocomposite
RK4 is typically employed at the base of rail ballast to whereby the geogrid locks the ballast into place to limit lateral movement and maintain tack alignment and the geotextile acts as a filter to prevent the intermixing of soils with the ballast layer maintaining the integrity of the drainage system.
The rapid passage of trains applies dynamic loads to the soil resulting in very intense compression and decompression cycles. The foundation, being thus subjected to fatigue stresses, can undergo fracturing up to the point of collapse. Under these conditions, both very thick layers of aggregate, and frequent and expensive maintenance are required and although these maintenance costs are high, by far the most important cost factor is the reduction in revenue caused by the disruption of services. RK4 laid on the base of the railway ballast, constrains the aggregate by laterally confining it, and creating the necessary trackbed stiffness. The aggregate’s thickness may therefore be reduced to give construction cost savings.
RK4 uses RK1 needlepunched nonwoven which is specified by engineers due to its robustness and its proven ability to function in the most demanding conditions – especially important under dynamic loading beneath track ballast. Extensive testing has demonstrated RK1’s class leading robustness and long service life under dynamic loading conditions. This is due to its; high puncture resistance, high elongation to break, superior abrasion resistance, excellent filtration characteristics at all strains and high UV resistance.
RK4 allows the installation of both the geotextile component and the grid at the same time, giving a product that will function for ballast confinement, soil filtration and separation.