AbstractThe gradation and water content have a significant influence on the resilient modulus of strongly weathered phyllite subgrade. In this study, small-scale plate loading tests were conducted on large cylindrical specimens 600 mm in diameter and 450 mm high during the saturation process. The specimens comprised strongly weathered phyllite with varying rock content (0%, 35%, 55%, and 75%). The volumetric water content of each specimen was monitored continuously during the tests. The results demonstrated that the moisture migration rate was largest during the first 5 days of saturation, and the resilient modulus decreased sharply. This was followed by a slight increase in the resilient modulus during the next 10 days of saturation owing to the optimal structure induced by the test loading condition. The results also demonstrated that the resilient modulus of the coarser-grained specimen decreased slightly during the saturation process. A numerical model was established to analyze the stress state of asphalt pavement structure considering the reduction in subgrade resilient modulus. The results obtained from the numerical model indicated that the reduction in subgrade strength could lead to a significant increase of pavement deformation and shear stress.