Dynamic Stability of Existing Railway Subgrade under the Effect of Heavy Axle Load Trains

Abstract:

In order to study additional cumulative deformation and dynamic strength stability of railway subgrade under effect of heavy axle load train for existing railway lines, typical subgrade soil was selected to conduct cyclic triaxial tests to obtain the variations of cumulative plastic deformation and threshold stress under various physical states and cyclic loading conditions. Consequently, the prediction formula of cumulative strain was established. On this basis, by dynamic finite element method and layerwise summation method, dynamic stress and additional settlement of subgrade under heavy axle load were calculated. The conclusions are as follows: subgrade settlement rises rapidly with increasing in the axle load in conditions of low compaction or high saturation, and moreover, the settlement rises significantly when axle load exceeds 27t; but when the compaction coefficient is larger than a certain value, the increase of axle load has a smaller effect on subgrade settlement; the influential depth of additional settlement in subgrade under heavy axle load is mainly within 2.5m from subgrade surface, especially within 1.0m; under heavy axle load, subgrade may generate unacceptable permanent deformation even it meets the threshold stress condition. To reduce subgrade additional deformation and its duration under heavy axle load, the compaction coefficient or strength of subgrade should be improved.