Long-Term Deformation of Highway Subgrade under Coupling Effect of Traffic Load and Drying–Wetting Cycles

Subgrade long-term deformation was investigated by taking the effects of both traffic load and drying–wetting cycles into consideration on the basis of numerical calculation and laboratory experiments. The total subgrade long-term settlement is composed of three parts: traffic load induced cumulative plastic deformation derived by calculated dynamic stress, deformation generated by dissipation of pore water pressure and attenuation of subgrade modulus due to drying–wetting cycles, and vertical deformation induced by weather cycles. The effects of the number of drying–wetting cycles and cycle amplitude, subgrade soil static shear strength, confining pressure, compaction degree, static constant load above the subgrade, and number of load cycles were taken into account to establish the subgrade deformation model. The layerwise summation method was also used to calculate the subgrade cumulative plastic deformation. Furthermore, a selection of computation results of the three deformation components was shown in detail and the impacts of number of load cycles, degree of compaction, subgrade depths, and the characteristics of drying–wetting cycles on the long-term deformation were discussed using the proposed model.