Abstract: The Harbin to Dalian Passenger Dedicated Line (HDPDL) is the first high-speed railway designed, constructed and operated in cold regions in China. The unique engineering geological condition along the HDPDL and the stringent engineering requirements pose severe challenges to the stability of subgrade in cold regions. In order to monitor the stability and freezing characteristics of the subgrade, the typical subgrade sections are selected in different freezing zones. The structure style of subgrade has a remarkable disparate impact and restriction on the freezing characteristics of high-speed railway subgrade in cold areas through analyzing the monitoring data of the first freezing and thawing period after operation. By comparing the middle section of cutting with the embankment near the entrance and exit of cutting, it is found that in this embankment section, there exists thicker frozen interlayers for a long time. The temperature difference between the cutting and the embankment increases with the increase of latitude. It is also found that there is a certain thickness of high-temperature frozen soil in embankment in April every year. In the same region, the maximum freezing depth of embankment is 20 to 50 cm deeper than that of cutting. However, the maximum deformation of cutting is 2 to 5 mm larger than that of embankment, and this difference becomes larger as latitude increases in spring thawing period, the change rate of frozen depth of cutting section fluctuates dramatically around 0; at this moment, the deformation exhibits a rise in mutation manner while the freezing depth change rate of embankment is located in the range of negative, and the obvious mutation in deformation of embankment is not be observed.

Key words: cold regions, high-speed railway, subgrade, ground temperature, deformation, structure style