Abstract: According to the long-term monitoring data of the Qinghai-Tibet Highway from 2004 to 2011, we systematically analyze the characteristics of permafrost embankment deformation and the reasons of roadbed disease. Our studies show that the thawing-sinking is the major deformation behavior of common fill embankment, and the settlement may be further increased in future. The types of deformation can be divided into uniform and non-uniform deformations in terms of the deformation rate differences of each part of embankment. The average deformation rate is in the range of 0.2-5.5 cm/a. The deformation rates of embankment are different in different regions. In river valley regions, the deformation rate is the maximum; it is followed in the mountain regions, and the minimum is in other regions. The types of deformation can also be divided into longitudinal and lateral embankment deformations depending on the deformation direction. The longitudinal embankment deformation has the greatest effects on the pavement and results in the wave-shaped pavement disease, which induces uncomfortable driving situations and the road traffic safety. The lateral embankment deformation results in longitudinal cracks in embankment, which causes the collapse towards to the severe deformation side, and thus influences its overall stability. Based on the investigation of the Qinghai-Tibet Highway roadbed diseases in 2012, it has been found that the proportions of embankment status grades of very good, good, fair, poor and very poor are 57.39%, 28.12%, 9.71%, 4.60% and 0.17%, respectively. This study provides a reference for maintaining the stability of Qinghai-Tibet Highway and a basis for route selection and engineering design in future.

Key words: Qinghai-Tibet Highway, embankment deformation, embankment disease, embankment condition index (ECI)