Reducing railway track settlement using three-dimensional polyurethane polymer reinforcement of the ballast

• First time track settlement behaviour of polyurethane ballast reinforcement presented.
• Significant reductions in track settlement using polymer GeoComposites possible.
• Rebound of the GeoComposite observed illustrating elastic behaviour of the geopavement.
• Application of the research technique at real railways sites confirm laboratory studies.

This paper presents the measured settlement results of full-scale testing of unreinforced and polymer reinforced ballast railway track under laboratory conditions, using the GRAFT I (Geopavement and Railways Accelerated Fatigue Testing) facility to show the significant reduction in track settlement that can be obtained using in-situ ballast reinforcement techniques. The measured settlement profile of each track specimen is monitored up to a maximum of 500,000 load cycles at different load levels and formation conditions, ranging from a subgrade Young’s modulus of 25–51 MPa. The results of a 3-dimensional polyurethane ballasted track reinforcement technique called XiTRACK, at an equivalent axle load of 44.4 tonnes, are then directly compared to the unreinforced settlement profile using developed settlement models from the tests. The polymer treated track is observed to reduce permanent track settlement by 99%, effectively giving slab-track like performance. The free draining properties of the formed GeoComposite are also highlighted. The paper concludes by presenting and commenting on, the application of the technique to real UK Switch & Crossing sites on the West Coast Main Line and at Clapham Junction. In the former case, at Points 215D, the application of the technique eliminated the need for track maintenance over the 10 year operating cycle at axle loads of 25 tonne and main line speeds of 125 mph confirming the measured laboratory observations.