ENVIRONMENTAL AND ENGINEERING GEOLOGY OF THE BEI'AN TO HEIHE EXPRESSWAY IN CHINA WITH A FOCUS ON CLIMATE CHANGE

The Bei'an to Heihe Expressway in China is located in southern boundary of high latitude permafrost. In recent years, this expressway has experienced increasing roadbed settlement, salutatory flow ice and cut slope landslides in the road area, which threaten the stability of the subgrade and highway operational safety. The morphological characteristics and evolution of the above phenomenon are related to permafrost distribution and degradation as well as seasonal freeze-thaw. The relationship between the annual average temperature change and the permafrost distribution are analyzed based on the annual average temperature from 1954 to 2011 in Sunwu County, and the cumulative monthly average air temperature, ground temperature, precipitation, and maximum frozen soil thickness in Sunwu County from 1971–2000. Uneven settlement of the roadbed and salutatory flow ice caused by freeze-thaw, as well as landslide mechanisms and motion characteristics were analyzed. The analysis used ground temperature, moisture, surface and landslide deformation monitoring data from 2009–2012 in the Bei'an to Heihe Expressway sections K161+440, K161+860, and K178+530, which traverses the north section of the Lesser Khin-gan Mountain. The results of this study demonstrates that in the past 50 years, the annual average temperature in the Sunwu region had an upward trend, and after 1995, when the annual average temperature in the region rose to above 0°C, the permafrost degradation process accelerated. Landslides, roadbed settlement, and salutatory flow ice in the road area are often influenced by atmospheric precipitation, melting permafrost, seepage water, air temperature, geological condition, and human activity. These geological problems are affected by seasonal temperature changes, slope water content change, and other related geological conditions, and have the characteristics of being low angle, intermittent, and creeping.