Deformation Characteristics of Track Structures for Level Crossings Subjected to Heavy Forklift Load

Abstract

Level crossings or paved ballasted tracks laid in freight train container yards are subjected to train loads and forklift loads. Those asphalt pavements in the level crossings or paved ballasted tracks are designed using performance-based design method. Nevertheless, in the conventional design for ballasted tracks itself at the level crossing or paved ballasted tracks in the freight container yards in Japan, truck loads or forklift loads are generally not taken into account, and therefore, heavy duty truck loads or 12ft-container-forklift loads had not induced a typical problem to level crossing structures or paved ballasted tracks. However, because of the recent increase in the transportation of the large marine containers on freight trains, very large forklifts have been increasingly introduced to freight container yard. Maximum wheel loads of those large forklifts reach up to 500kN. Consequently, damages to level crossings and paved ballasted tracks in freight container yard are increasing. Concrete slab tracks are considered to be effective track structure to reduce the deformation of roadbeds or subgrades which are subjected to heavy forklift loads. However, to maintain the concrete slab tracks in the freight container yards in a decent condition, it is necessary to design the roadbeds and subgrades properly to avoid excessive deformation, because once the deformation are induced bebeath concrete slab tracks, it is not easy to correct track irregularity. To deal with above issues, deformation characteristics of subgrades, roadbeds and track structure under the heavy forklift loads were investigated using small scale model tests and full scale model tests in this study. In the scale model tests, moving wheel loads were applied to an asphalt paved ballasted track model and concrete slab model. In the full scale model tests, train loads and heavy forklift loads were applied on the asphalt paved ballasted track and concrete slab track. Through those tests, it was confirmed that the load applied by heavy forklift have predominant effect on the deformation characteristics of asphalt paved ballasted track. Besides, it was confirmed that the concrete slab track effectively reduces the vertical stress applied on the roadbed and subgrade.