Reinforcement and mud-pumping benefits of geosynthetics in railway tracks: Numerical analysis

Laboratory tests were conducted on track materials to evaluate constitutive parameters for three different sets of constitutive relationships, namely, non-linear analysis, straight analysis and coupled analysis. The model test results of finite element analyses using various constitutive relationships are compared. The coupled analysis provided a better prediction of the measured results compared to the non-linear and straight analyses. A detailed parametric study of a prototype track was then performed using the coupled analysis to evaluate the effects of geosynthetics on track reinforcement and mud-pumping reduction.Geogrid reinforcement was found to significantly reduce tie displacement only at low subgrade modulus values and effective subgrade shear strength parameters. Geogrid reinforcement was equally effective at reducing tie displacement within the subballast thickness range of 450–1000 mm. High excess pore water pressure coupled with low effective cohesion gives rise to mud-pumping problems in silty soil subgrades. The provision of geotextiles at the subgrade surface facilitates quick in-plane drainage and dissipation of pore water pressure. Thus, excess pore water pressure was observed to be lower in a geotextile-stabilized track compared to that in an unreinforced track, indicating reduction in mud-pumping potential in the former.