In this paper, we investigate the mechanical behaviour of a compressed air energy storage (CAES) pile through finite element analyses. A simple hypoplastic constitutive model is used for the soil surrounding the pile. The analyses are carried out on two numerical models, namely a plane-strain model and an axisymmetric model. The numerical results show that the internal pressure of the pile has only minor influence on the stress state in the surrounding soil. The radial deformation around the pile is much smaller than the vertical deformation during the pressurization. Moreover, an increase of the internal pressure induces pile expansion around a neutral point in middle of the pile. This gives rise to relative displacement at the pile-soil interface, leading to upward slip at the pile head and downward slip at pile tip. The shear stress between pile and soil is also considered.