Abstract: Based on the centrifuge model test, models of subgrade upon slope in permafrost area are completed using the mechanical similarity. Impacts of soil mechanical parameters, subgrade height and ground gradient on the deformation characteristics and stability of subgrade are researched. As well as the deformation failure mechanism and failure modes are researched by comparing rubble stone subgrade and ordinary subgrade. The results show that the soil mechanical parameters, the subgrade height and the ground gradient have obvious effects on the stability of subgrade. The deformation mutation point takes place at the freezing-thawing interface; and the deformation mainly concentrates on the soil layer above the freezing-thawing interface. Under the experimental conditions, the reasonable subgrade height is about 5 m. With the subgrade height of 5 m, the critical value of the ground gradient is about 1:6 and the transverse deformation increases. Both vertical and transverse deformations due to permafrost thawing show a positive nonuniform feature. The essential cause of failure is the deficiency of shear resistance strength of the weak belt. The soil layer above the freezing-thawing interface slips along the freezing-thawing interface. Failure modes of the subgrade are divided into cracking failure in shallow layer, cracking failure in deep layer and failure of integral slippage. Besides, the horizontal displacement and settlement of the rubble stone subgrade are smaller than the ordinary subgrade; and the rubble stone subgrade has better whole stability.

Key words: permafrost, slope subgrade, centrifuge model test, stability, deformation characteristics