Vertical Track Irregularity Caused by Subgrade Settlement and Its Design Criteria for High-speed Railway

摘要

Vertical track irregularity mostly comprises short -wave rail surface erosion caused by vari -ous reasons and long-wave r permanent deformation caused by subgrade settlement. In this study, first,the development of subgrade settlement due to r repeated train traffic is investigated. A unified constitutive model of geomaterials is developed to describe the residual r deformation of ground soil and embankment's granular fill under cyclic loadings. Thereafter,a full-scale physical model r testing with dynamic loading up to 10ton was carried out in the laboratory on a railway model with 15 m * 5m * 6m r dimensions,using harmonic periodic wave to simulate one wheelset loadings. Results show that acceleration of track structure r and dynamic stresses of subgrade vary significantly with excita -tion frequency. And there exists a critical frequency and r peak frequency ,corresponding to the maximum growth rate and maximum value respectively. Subgrade settlement under different r excitation frequencies occurred in the physical model is predicted , using the proposed numerical computation model. r Finally,a lumped-mass train mode coupled with slab track is used to discover the relation -ship between vertical railway r irregularity caused by subgrade settlement and train 's dynamic responses when train passes by a railway location with r certain type of subgrade settlement. Some design criterias for a reliable railway subgrade are proposed from the point view r of train running quality.