About Permafrost

Frozen Ground in China

About 75% of the area of China experiences ground freezing.A recent map of frozen ground in China shows that the total area of permafrost in China is estimated to be ~ 1.59*10⁶ km² (glaciers and lakes excluded), while the area of seasonally frozen ground (excluding instantaneous frozen ground) is ~ 5.36*10⁶ km². The total area of high-altitude (plateau and mountain) permafrost in China is~ 1.35*10⁶ km², of which the area of mountainpermafrost is ~ 0.30*10⁶ km² and the area of plateau permafrost is ~ 1.05*10⁶ km². Latitudinal permafrost is located in the northern part of northeastern China, and itsarea is ~ 0.24*10⁶ km² (Ran et al., 2012; Fig.1).

Permafrost in China has warmed in the past few decades. Permafrost temperatures have increased and the thickness of permafrost has decreased. A significant increase in thickness of active layer has been verified by long-term ground temperature observations at various sites.

Permafrost Engineering in China

To deal with railway construction on warm and ice-rich permafrost, academician Cheng proposed a roadbed cooling approach for the

construction of Qinghai–Tibet Railway. The key to the success of the construction lies in preventing thaw of permafrost beneath the 

roadbed. Based upon the experience and lessons learned from roadway construction over permafrost, Cheng (2005) proposed a more 

proactive design approach for the construction of the Qinghai–Tibet Railway. This approach focused on cooling down the roadbed by 

lowering the ground temperature and differs from the passive method of preventing permafrost from thawing by simply increasing 

thermal resistance (e.g., increasing embankment height and using insulating materials). This roadbed cooling design approach is 

especially relevant to warm and ice-rich permafrost areas. Cheng and his colleagues developed a number of measures to cool down 

the roadbed, including proper selection of roadbed material and configurations to adjust solar radiation, heat convection, and heat 

conduction patterns in and/or around the roadbed (Fig. 2).