This study investigates the deformation characteristics of belled piles under different loading conditions using 1- \(g\) physical modeling tests and Material Point Method (MPM) simulations. A 3D-printed polypropylene model pile, designed based on scaling laws, was employed to ensure experimental validity relative to prototype behavior. Key findings from the physical experiments include: Enlarging the bell diameter markedly improves ultimate uplift capacity but has negligible effects on lateral deformation under pure lateral loading. Under combined uplift-lateral loading, pile failure is predominantly controlled by horizontal displacement, underscoring load-component interactions. Complementary MPM simulations analyzed the soil influence zone around the pile, demonstrating that larger bell diameters extend the failure mechanism’s spatial extent, thereby enhancing bearing performance. This combined experimental–numerical approach offers actionable insights for optimizing belled pile designs to maximize pullout resistance.
