Field Validation of Polyurethane Technology in Remediating Rail Substructure and Enhancing Rail Freight Capacity

The structural integrity of rail substructure can be compromised due to ballast fouling thus leading to poor ride quality, track instability, and potential train derailment. This problem is quite costly for the railway industry as it increases maintenance costs, creates operational downtimes, and generates conditions for potential train derailment events. A creative procedure to reduce the detrimental effects of ballast fouling is the application of polyurethane (PUR) as a void-filling and particle-bonding technology. This study assesses the use of expanding rigid PUR foam to remediate substructure deficiencies in railroad track at field-scale. The investigated site is constructed on a 3-m-high embankment, has a length of 80 m with standard rail gauge, and was historically used to stage coal cars. Field investigation profiles showed the presence of soft, wet subgrade beneath the ballast/subballast. Railway substructure condition was evaluated by measuring the track modulus (u) before and after injection. Track modulus is considered as a representative parameter to quantify the structural integrity of a railway track system. The track rating improved from a “poor” (u = 8 MPa) initial condition to an “average” (u = 15.2 MPa) condition after injection, which represents a 90 % improvement in track modulus. This field study shows the potential of using strategic injections of rigid PUR foam to remediate railway substructure in localized sections of track, such as at frogs, intersections, and bridge approaches.