In-situ investigation on mud pumping in ballastless high-speed railway and development of remediation method

Abstract

Mud pumping induced by intensive precipitation and traffic loading is a typical distress in high-speed railway either for ballasted or ballastless tracks. In this study, in-situ investigations, numerical simulation and laboratory tests were conducted to reveal the formation of mud pumping and to explore an appropriate method to remediate mud pumping in ballastless railway. Field investigations and numerical simulation indicated that there was a whipping effect in the dynamic responses of the slab track due to train passages, which induced detachments at the end of concrete base from the roadbed surface. This detachment provided infiltration routes for rainwater into the roadbed layer and initiated the mud pumping. An evaluation method was proposed to analyze particles stability of roadbed materials taken from the investigating site, and the results indicated that instable finer particles promoted an increasing instability of coarse particles. Based on the characteristics of particle stability of roadbed materials and the formation process of mud pumping, an optimized polyurethane chemical injection (PCI) method was proposed to remediate mud pumping and tentatively applied to a mud pumping reproduced ballastless slab track in the full-scale physical model test. Both static and dynamic performances of the remediated ballastless track were restored to their initial values before the occurrence of mud pumping. The accumulative track settlement was less than 2.2 mm even under more than one million train loads, indicating that the PCI method is effective in mud pumping remediation of ballastless slab track.