A Case Study On Embankment Stability Of High-speed Railway Cold Regions

In china,seasonally frozen soil is everywhere,and many railways that have been or are under construction are located in seasonally frozen soil area.Due to the seasonal frost heave and thaw settlement of subgrade,irregular deformation occurs from time to time along the subgrade;which brings great challenge to the stability control of China’s high-speed railway subgrade.This paper studies the frost heave deformation law of seasonal high-speed railway subgrade in northwest China.Frost heave is an important research topic,because it will affect the safe and stable operation of high-speed railway in cold regions.Based on the temperature,moisture,and deformation data of K1962+168 monitoring section of Lanzhou-Xinjiang high-speed railway from2015 to 2016,this paper analyzes the deformation law and influencing factors of subgrade of highspeed railway in cold region.Unveiling the structure of hydrothermal interaction,hydrothermal dynamic observation,frost heaviness,and freezing depth was performed in the field for 1 year.Results showed that the temperature gradient is changing rapidly at a rate of(4-5)°C from summer to autumn and the freezing rate is fast(6.5-7)°C at the start and slow(2-3)°C during the deep frozen period from December till February,moisture can have enough time to migrate to the freezing front ranging 12-16% and produce increased frost heaviness of 18-20 mm during this frozen period.The reduction of liquid water in unfrozen soil is closely related to where the freezing front is located.The largest frost heave 1.13 mm occurs in the middle layer(0.5–1.5m).The monitored results also show that the frozen depth increases as an exponential time function and in 2015–2016 the maximum frozen depth in the embankment reached 2.5 m.Increasing frozen depth could foster the development of the frost heave,which was observed in different depths at three layers(0–0.5m,0.5–1.5 m,and 1.5–2.7 m),along with variations in the moisture content and ground temperature.The hydrothermal effect directly causes many damage-freezing engineering problems during soil frost heave.The findings of this study have some theoretical significance in revealing the heat and fluid flow in seasonally frozen soil region,analyzing the freeze-thaw mechanism.For a few study results,it is possible to refer to the fact that the frost heave characteristic of the embankment filled with coarse-grained soil and the relationship between ground temperature,water content and frost heave quantity can provide a better understanding of the frost heave mechanism of the high-speed railway embankment,to benefit the high-speed rail design at high altitude and seasonally frozen regions.