The Effect of Permafrost Preservation of Different Height Subgrade in Permafrost Regions

The effect of permafrost preservation of different height subgrade in permafrost regions is studied in the paper. After highway and railway are constructed in permafrost regions, heat exchanging system is changed, permafrost table is dropped. It is an important factor to subgrade stability. Over 560 km route of the Qinghai-Tibetan railway is constructed in permafrost regions. How to guarantee subgrade stability is a major issue. Two embankment heights (1.0 m and 1.5 m) in the Qingshuihe test site are chosen to monitor the characters of ground temperature and the temperature upper and below the board, and deformation of embankment surface. Expanded Polystyrene (EPS) boards are laid 0.5 m above the ground floor. The result shows that the natural upper limit of perennially frozen soil is 2.42 m under the ground; upper limit raise to 1.31 m in 1.0 m height subgrade and 1.05 m in 1.5 m height subgrade after laid the boards; Materials have a good themal-insulation property; Variation of temperature is large between upper and lower the EPS board. Board in lower embankment heat insulation performance is way beyond in higher embankment. General trend is thaw collapse. total deformation and differential deformation in the higher embankment is larger than the lower. Lower embankment excelled the higher embankment. the discipline of attenuation should be study.