Analysis of cyclic deformation and post-cyclic strength of reinforced railway tracks on soft subgrade

Abstract

Intensive urban growth leads the need of rail road tracks to be constructed on marginal soils as well as soils with very low strength. Application of geosynthetic has been shown to be effective in reducing excessive settlement and lateral displacement of tracks over soft subgrade under cyclic loading. Tests were performed on full paneled 1:3 scale model railway tracks to evaluate deformation and post-cyclic strength of geosynthetic reinforced railway track on a soft subgrade. The deformation pattern of the model track in rail and sleeper direction was also traced from the laboratory model tests. From the model tests, it is also confirmed that, after cyclic loading the modulus of the track has been increased, nevertheless, the increment of subballast thickness also increases the stiffness of the track. A generalized bilinear log–log model is proposed for the prediction of tie deflection with number of load cycles for fine-grained soils. An attempt has been made to incorporate the existing methods applicable for predicting cumulative plastic deformation for fine grained soils to the prediction of tie deflection. The cyclic response of the laboratory models were also well supported by the predictions of the three-dimensional finite element analysis. Comparisons between predicted and experimental results show good applicability of the improved method. The results exhibit that the geosynthetics reinforcement can be effectively used to improve the performance of railway tracks on clayey subgrade.