Quantitative Study on the Influence of Runway Compaction and Structural Design Parameters on Cumulative Settlement of the Silt Subgrade

Airport pavement damage is mostly caused by the cumulative effect of subgrade settlement, but existing calculations for subgrade cumulative settlement seldom consider the dynamic variation characteristics of the degree of compaction of subgrade soil under repeated loading. Accordingly, based on the proposed modified bounding-surface model for silt, numerical simulations of runway cumulative settlement under cyclic impact aircraft loading are performed. The study first reveals the quantitative influences of pavement structural parameters on runway cumulative settlement under conventional layered compaction of subgrade. Then, under different structural parameters, the differences in runway settlement between overall and layered compaction of subgrade are compared quantitatively. The following conclusions are drawn: First, as pavement parameters increase, the influence of parameters of the surface layer and the thickness of the base course increases greatly, whereas the influence of the elastic modulus of the base course decreases. Second, the maximum increments of cumulative settlement and its change rate induced by the layered compaction form are 63% and 88%, respectively. As the thickness of the surface layer exceeds 0.36 m, the influence of compaction form can be neglected. Therefore, appropriate ranges of pavement parameters can effectively decrease the effect of compaction form. Third, as the thicknesses of the surface layer and the base course are less than 0.31 m and 0.28 m, respectively, and the elastic modulus of the base course is greater than 1.6 GPa, the sensitivity of settlement to changes in pavement parameters is less affected by different compaction forms, and the influence of the compaction form can be ignored in optimization of the elastic modulus of the surface layer.