To avoid pavement structure failure induced by subgrade settlement

index and criterion for settlement control applicable to cut-and-fill subgrade for mountain-highways are studied. Firstly

the Prony series expressions for three-dimensional Merchant model are deduced based on constant Poisson’s ratio hypothesis; and the settlement calculation models of cut-and-fill subgrade were established with ABAQUS. The calculations indicate that post-construction settlement curves of cut-and-fill subgrade are spoon-shaped or S-shaped. The difference in curve shape reveals the time-space coupling effect in subgrade settlement. Secondly

the following hypothesis is proposed based on post-construction settlement mechanisms: the post-construction settlement curves of cut-and-fill subgrade are central symmetric S-shaped curves composed of two parabolic segments. The mechanical response of asphalt pavement under parabolic subgrade settlement indicates that the additional flexural-tensile stress is linear with quadratic term coefficient of parabolic equation which

consequently

can be adopted as settlement control index applicable to cut-and-fill subgrade. Finally

the method of defining settlement control criterion applicable to cut-and-fill subgrade is presented based on the failure modes of asphalt pavement under traffic load and subgrade settlement. The research findings provide a technical foundation for post-construction settlement control of cut-and-fill subgrade.