The frost heaving deformation of high-speed railway subgrades in cold regions:Monitoring and analyzing

Harbin-Dalian High-Speed Railway,crossing Northeast China,is the first new-built and operating high-speed railway in cold regions around the world. The subgrades of the railway were treated with filling material replacement and taking waterproof measures and so on to prevent frost damages. For evaluating the effects of the frost heaving prevention and engineering operation status of the subgrades,the monitoring data during the first freeze-thawperiod( 2012- 2013) from 9,641 monitoring points along the railway were analyzed. The occurrence,development and changing of the frost heaving were summarized. It is found that the development of the frost heaving includes the rapid growing stage,the stable frost heaving stage and the thawing settlement stage. The frost heaving deformation occurs along the whole line,but the frost heaving amount,great or small,is under control. The frost heaving degrees are related to the subgrade structures. The frost heaving occurs mainly in shallowpart of a subgrade base,and its damage degree depends on the subgrade structure. On the whole,the frost heaving in the transition section is slight,followed by that in the embankments,and it is most serious in the cutting sections or in the base-plate jointing parts. As engineering treatments against frost heaving,it is suggested to focus on reducing surface water infiltration and control frost heaving deformation of the subgrade base. And in the designing of high-speed railway in seasonal frozen soil regions,bridges are strongly recommended instead of subgrade,and to modify the upper layer of the subgrade to no frost heaving structure.