Model tests and numerical analyses on the mechanism of flow-out of railway ballasts induced by flood inundation

Recently in Japan, railway ballasts have been flown out several times by heavy or intense rainfalls. However, the mechanism has not yet been investigated in detail, so that the risk and the countermeasures cannot be reasonably proposed. Therefore, in this research, model tests and numerical analyses were conducted to investigate the flow-out mechanism. It was found that the seepage characteristics of ballast beds can be expressed based on Forchheimer law not on Darcy law. Progressive failures were observed in the model tests. It was also found that the stability of the ballast beds can be reasonably explained by the proposed micro-mechanic approach.