2005 Volume 45 Issue 4 Pages 99-118
To develop a relevant performance-based design method for railway asphalt roadbed, the resilient and residual deformation characteristics of railway roadbed and subgrade were investigated by means of scale model tests. In the scale model tests, the difference in the mechanism between moving-wheel loading and fixed-point loading were discussed. The deformation characteristics of roadbed and subgrade in the fixed-point loading which apply cyclic vertical load at a fixed point on rails above a certain sleeper was proved to be substantially different from the trend in behaviour when moving a wheel repeatedly on a model rail as in the full scale railway track. Therefore, it was con-cluded that the moving-wheel loading test is necessary to investigate the deformation characteristics of railway roadbed and subgrade. On the other hand, the result of moving-wheel loading test showed that the resilient deformation characteristics do not change even residual deformation caused by repeated loading. A resilient deformation characteristic of asphalt roadbed is an important factor because the fatigue criterion of asphalt concrete is specified in terms of resilient tensile strain. The resilient deformation characteristics of asphalt roadbed, including the maximum resilient tensile strains in the asphalt concrete layer, were simulated well by linear elastic FEM analysis using exact boundary condition and relevant material parameters described in this paper.
