Effect of structures and sunny-shady slopes on thermal characteristics of subgrade along the Harbin-Dalian Passenger Dedicated Line in Northeast China

- The structure styles of subgrade have the inverse influence to the frozen depth and the amount of frost heaving.
- The effect of sunny--shady slope in coarse filling materials, which could made a double frost heaving amount.
- The distribution and changing process of frost heaving along the HDPDL has been investigated
- The residual value of frost heaving in the shoulder shows a notable characteristic in subgrade.

The Harbin-Dalian Passenger Dedicated Line (HDPDL) was the first high-speed railway in typical middle-deep seasonally frozen regions in Northeast China. One typical feature of the HDPDL was that the subgrade length (231.245 km) accounted for 25.58% of the total railway length (904 km). Considering the condition of transition sections between subgrade and bridge, culvert and tunnel, thermal regime under them would severely restrict the subgrade stability and irregularity in winter. So, an auto-monitoring system has been set up at several typical cross-sections along the HDPDL. The analysis results indicated that in the first freezing-thawing period after operation, the maximum frozen depth (MFD) under the subgrade shoulder increased as latitude increased, and that the time of reaching the maximum frozen depth showed a similar trend. But the amount of frost heaving of subgrade shoulder showed a different pattern. The ground temperature and deformation characteristics were significantly different under the subgrade structure styles and the sunny-shady slope effects. At last, based on a long-term estimation, that applied the amount of frost heaving needs more carefully.