Soil arching has a significant effect on the behaviour of pile-supported geogrid-reinforced embankments due to its complex mechanics. In this study, a three-dimensional finite-element model was established to investigate the development of soil arching during the construction and static loading test on an embankment. The model was verified by comparing the variations in earth pressure on the pile cap with the measured data from well-instrumented full-scale model tests. A good agreement was found between the computed and measured data. The experimental and numerical results consistently showed that the arch foot moves from the edge to the centre of the pile-cap under static loading. Finally, the stress contours are presented to illustrate the development of soil arching during the processes of embankment construction and static loading.