The soil arching effect is the key mechanism for load transfer in pile-supported reinforced road (runway) foundations. In order to investigated the formation and evolution process of soil arching effect in the whole process of embankment filling and soft soil foundation consolidation, a three-dimensional hydro-mechanical coupled numerical model of PHC pile reinforced soft soil runway foundation was established based on the foundation treatment project in Pudong Airport. The variation laws of soil settlement, pore water pressure, and pile soil stress were analyzed, and the influence of pile spacing was considered. These data from both numerical simulation and field test indicate the soil arching effect in the foundation reinforced by PHC piles and preliminary reveal the evolution of soil arching in the process of embankment filling and soft soil foundation consolidation. The preliminary results encourage the authors to continue this research to investigate the evolution of soil arching under aircraft dynamic loads through adding a more suitable constitutive model or subroutine in this numerical model.