Where track needs to be constructed over soft subgrade with a poor load bearing capacity the use of large aperture high modulus geogrids has been proven to reduce ballast settlement and maintain track geometry.
GEOfabrics’ RK4 combines the filtration performance of RK1 with large aperture geogrids for optimal performance and improved installation times. The high elongation of the RK1 ensures that the ballast is able to interlock with the geogrid, thus preventing lateral movement and thereby reducing settlement.
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 (although these maintenance costs are high, by far the most important cost factor is the reduction in revenue caused by the disruption of services). GEOfabrics’ RK4 geocomposite laid on the base of the railway ballast, constrains the aggregate by laterally confining it, and creating the necessary tensile forces. The aggregate’s thickness may therefore be reduced to give cost savings.
GEOfabrics’ RK4 allows the installation of both the geotextile component and the grid at the same time, giving a product that will function for confinement for ballast and provide filtration and separation.