Three-dimensional response of saturated ground to expansion of airbag pile

Abstract Airbag piles have been widely adopted for ground improvement and deformation control in soft soil areas owing to their simple construction and good performance. However, analytical methods for predicting the additional stress and displacement induced by their expansion in saturated soft ground remain unavailable. In this study, the expansion behavior of an airbag pile in a three-dimensional saturated foundation is first analyzed using the principle of minimum potential energy to derive the expansion load acting on the surrounding soil. To evaluate the resulting stress and displacement fields in cylindrical coordinates, a double-layer foundation model is established. Two potential functions are introduced, and through Fourier expansion, Hankel transform, and recurrence relations of Bessel functions, analytical solutions for displacement and stress based on Biot’s poroelastic equations are obtained. Numerical solutions are computed with MATLAB after applying appropriate boundary conditions. The saturated foundation is degenerated to an elastic foundation, and a corresponding finite element model is developed using ABAQUS. The additional stress and displacement responses computed by the proposed method are consistent with FEM results, validating its reliability. Furthermore, the computed pore pressures agree with existing theoretical and field data. Finally, parametric effects on displacement and stress responses are investigated. The proposed method serves as a preliminary analytical tool for assessing the mechanical effects of airbag pile expansion in soft saturated soils, providing theoretical insights into the key governing factors.