Performance-based design method for railway asphalt concretereinforced roadbed

Resumé

The asphalt roadbed (asphalt concrete-reinforced roadbed) is widely used for ballasted tracks in Japan, primarily to firmly support ballasted tracks and to reduce track irregularities. The current design standard of asphalt roadbeds in Japan does not take into account the effects of the number of train passing. To alleviate this drawback, it was necessary to develop a more rational performance-based design method that can reduce the total life cycle cost. It is considered that the new performance-based design of railway asphalt roadbeds should be based on fatigue criteria for asphalt concrete. In the design of pavement for highways, the fatigue criteria of asphalt concrete are specified in terms of maximum resilient tensile strains that are evaluated by multi-layer elastic analysis. However, it is not known whether the same methodology can be applied to railway roadbeds, which are subjected to much more complicated load conditions due to complicated track structures, composed of rails, sleepers and ballast. In this study, a series of scale model tests were performed to validate the three-dimensional elastic FEM analysis to evaluate resilient strains in the asphalt concrete layer in railway roadbed. On the ground of that, appropriate analysis procedure to obtain the asphalt concrete strain was proposed in present study. Thereafter, the service life of asphalt roadbed was obtained by new design method. It was confirmed that the current asphalt roadbed has a service life of 50 years in general high speed line in Japan.