Abstract
The railroad roadbed plays an important role in distributing and transferring the train loading to subgrade, preventing subgrade from being softened by providing appropriate stiffness for subgrade, and eventually supporting the track structures. Generally, around 40% of axial loading of train is resisted by rail-tie structure itself and the remainder is transferred to subgrade through the ballast. Therefore research on the load transfer mechanism is needed to optimally design the railroad. In this study, a series of prototype railroad roadbed tests were performed to investigate the earth pressure generated by axial loading of train with variation of the parameters and thickness of the reinforced railroad roadbed. In the tests, the measured earth pressures on the top and at the bottom of the reinforced roadbed were in the range of 25~59kPa and 30kPa, respectively. While the thickness of crushed stone reinforced railroad roadbed varied from 30, 50, and 80 cm the measured earth pressure ratio, was 51.6%, 41.3%, and 38.6%, respectively. This shows that the earth pressure decreased with an increase in the thickness of the railroad roadbed. It was also found that slag roadbed was more effective than the crushed stone roadbed in load distribution. The measured earth pressures in the tests were much smaller than those calculated by empirical and theoretical relationships because the axial loading were not well transferred due to the placement of the ballast without sufficient compaction, and the earth pressures from Talbot's empirical relationship were about twice those from RTRI's empirical relationship and Geotrack