Long-term settlement of railway embankment caused by repeated wetting and creep

초록

Recently, the high speed railway has come into the spotlight as important and convenient traffic infrastructure. In Korea, Kyungbu high speed train launched its operation over a 400km-section in 2004, and the Honam high speed railway is scheduled to open in 2015. Since the trains run at high speed(maximum design speed of 300-350km/hr), the differential settlement of trackbed might cause a fatal disaster. Even little settlement of the trackbed, hence, shall be carefully monitored. Particularly in case of concrete trackbed which is extremely difficult repairing the settlement, unlike the traditional ballast trackbed, the measures to prevent the settlement of the trackbed is more important. The settlement of the filling material after the track is installed is usually categorized into the settlement caused by the variation of the loads including traffic load and the settlement resulting from environmental factors such as the variation of temperature and water moisture content or creep occurred as time goes by under the constant surface load. The characteristics of compression of filling materials depend on a number of factors such as soil/rock type, as-compacted moisture, density, stress level and wetting condition. Because of the complexity of these factors, it’s not easy to quantitatively predict the amount of compression without carrying out the extensive tests. This study was intended to identify the effect of the wetting on a long-term compressive settlement of the filling material which was comprised the mixed soil and aggregate, depending on compaction and grading conditions. Consequently, the settlement under the fully-submerged condition reached to maximum 0.73%, and a repeated settlement was monitored when moisture content was increased repeatedly like the rainfall infiltration. In contrast, in case of the materials without fine fractions or compacted in wet condition, the settlement caused by setting was relatively low.