Polyurethane grouting materials with different compositions for the treatment of mud pumping in ballastless track subgrade beds: properties and application effect

Mud pumping in subgrade beds under ballastless tracks will deteriorate the dynamic performance of infrastructure under railway lines, reduce the smoothness of the railway lines, and seriously affect the comfort and safety of the trains. Due to their good mechanical properties, two-component polyurethane materials can be used for grouting to treat the fouling problems caused by ballastless track mud pumping. To develop a polyurethane formula suitable for the treatment of ballastless track mud pumping, we first performed indoor experiments to investigate the mechanical properties and gelation time of polyurethane elastomers synthesized with different raw material composition ratios, to determine an optimal composition ratio of the raw materials. Then, we conducted a dynamic field test to verify the remediation effect of the polyurethane material fabricated according to the design ratio. The results showed that polyurethane grouting material with the selected design ratios improved the contact characteristics between the surface layer of the subgrade bed and the base plate in the area, coordinating the dynamic response between the track structure and the subgrade bed. Thus, the obtained polyurethane grouting material could be used to renovate mud pumping areas of ballastless tracks with a good treatment effect.