MECHANISM OF REPEATED BALLAST SETTLEMENT OCCURRING AT THE SAME LOCATION

Abstract

 Even at the same location, it has been confirmed that track irregurality sometimes gradually returns to its original shape after tamping work for track maintenance, and the details of this mechanism have not been clarified. An investigation into this phenomenon using track inspection data revealed that this phenomenon is more likely to occur after tamping work using a hand tamper than a multiple tamper. To investigate the mechanism behind this phenomenon, a moving load test was conducted using a 1/5 scale model of the ballasted track after tamping work. As a result, it was found that local settlement was large in areas where the track elevation was locally large, and local settlement was suppressed in areas where the elevation was not locally large. Furthermore, analysis of the simulation using discrete elements models (DEM) revealed that when the amount of track elevation was large, the ballast density up to 100 mm below the sleeper did not become higher after tamping work, resulting in large settlement.