Dynamic responses of Qinghai-Tibet railway embankment subjected to train loading in different seasons

Compared with unfrozen soils, frozen soil has the most important characteristic-under natural conditions its matrix, which is composed of ice and water, changes continuously with varying temperature, which implies the mechanical properties of frozen soil are dependent on temperature. Accordingly, dynamic responses of frozen embankment under traffic load are different with the alternation of seasons. In order to clarify the definite seasonal difference, an indirect moisture, heat and dynamic coupled model of embankment in permafrost regions is deduced on the basis of principal theories of numerical heat transfer, physics of frozen soil, frozen soil mechanics and soil dynamics, meanwhile, its corresponding numerical program is also developed. Then, a common embankment section of Qinghai-Tibet Railway (QTR) is taken as an example, and while four typical seasons (January 15, April 15, July 15 and October 15) in the 50th service year are selected to carry out dynamic analyses and to reveal the seasonal difference in dynamic response. The results show that acceleration, velocity and displacement responses to train loading on October 15 are all the greatest in these four seasons. What's more, even after the train passes across the embankment section, there exist larger permanent displacement residing in the embankment and more damages to the toe of the embankment slope on October 15. Therefore, the deformation of QTR embankment should be monitored closely to ensure safe operation on October every year. Of course, the numerical model and results in this study may be a reference for design, maintenance and research on other embankments in permafrost regions. (C) 2011 Elsevier Ltd. All rights reserved.