The heat stability of embankment in the degrading permafrost district of Chang Shitou Mountain in Hua Shixia Valley is modeled. Critical heights of embankment for asphalt, concrete and gravel road surface along the National Road of Qinghai-Sichuang are figured out by computers, according to the natural geographical and geological conditions of Hua Shixia Valley. The modeled results are in good agreement with the field data on the Qinghai-Xizang Highway. The heat-stable critical heights of embankment for asphalt, concrete and gravel roads are figured out as 4.30, 1.40 and 1.00 m, in the 20th year following construction from regression analysis. Besides according to the calculation results, when the height of embankment is more than 5.0 m for asphalt road, there is an upper thawed core above the artificial permafrost table in embankment after more than 10 years following construction, although the artificial permafrost table under the road is located above the natural permafrost table in the whole process of road running. So the frost deformation of embankment would be increased and could not reach the requirement of deformation designing. But for concrete and gravel road, there is no upper thawed core in embankment (the heights of embankment are less than 5.0 m. Finally, the authors think that it is important that the running time after construction is introduced into the determination of the critical heights of embankment in cold regions, particularly more important in degrading permafrost regions. (C) 1998 Elsevier Science B.V. All rights reserved.
