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Geosynthetic Reinforcement for Railbeds
Geosynthetics are used to reduce or replace traditional layers in track-bed construction and rehabilitation worldwide to improve track support and reduce track maintenance costs. . Reinforcement geosynthetics, such as planar geogrids and three-dimensional geocells in particular, which rely on soil confinement, have demonstrated efficacy in stabilizing soft subgrade soils and reinforcing the substructural layers to limit progressive track degradation under cyclical loading. Reinforcement geosynthetics which rely on soil confinement increase soil bearing capacity, limit ballast movement and degradation and reduce differential settlement that affects track geometry. The increased use of geosynthetic reinforcement solutions is supported by high-performance geosynthetic materials (e.g., NPA - Novel Polymeric Alloy), published research, case studies projects and international standards, such as ISO WD TR 18228-5, ASTM D8269-21 , and CROW/SBRCURnet Pub. C1001 (in Dutch). The hybrid use of high-performance geogrids at the subgrade and high-performance geocell in the upper subbase/subballast layer has been shown to increase the reinforcement factor greater than their separate sums, and is particularly effective in attenuating heaving of expansive clay soils. . A field test project on a section of Amtrak's NE Corridor suffering clay mud-pumping demonstrated how the hybrid solution improved track quality index (TQI) significantly reduced the rate of track geometry degradation and track surface maintenance by factor of 6.7x. .Geosynthetic reinforcement is also used to reinforce railway embankments, which must be robust enough to withstand repeated cyclical loading. Geogrids in general and geocells in particular, can utilize recycled marginal or poorly graded granular material to create stable embankments, thereby making construction more economical and sustainable.