Deformation and instability of bridge pile foundations caused by adjacent surcharge loads in soft soil areas pose significant challenges to engineering safety. Existing numerical methods are insufficient in accurately simulating large soil deformations. A field test on a surcharge-pile foundation interaction was conducted, and numerical simulations were performed using both the conventional method and CEL (coupled Eulerian-Lagrangian) method. Key parameters of the surcharge load (e.g., distance and height) were analyzed based on the CEL method to evaluate their impacts on internal forces and deformations of the pile. Stress release holes were adopted as preventive measures, and their effectiveness under different layouts (single-row, double-row linear, and double-row plum blossom patterns) was compared. Results show that the CEL method is more suitable for simulating large deformations of soft soil induced by adjacent surcharge loads. The horizontal displacement of the middle pile decreases with increasing surcharge distance, while the pile-top displacement exhibits a nonlinear reduction as the surcharge height decreases. Stress release holes are effective in mitigating soil squeezing effects, with the double-row plum blossom layout achieving the best control performance compared to single-row and double-row linear layouts. The CEL method is validated as a reliable approach for analyzing internal forces and deformations of pile foundations under adjacent surcharges. This study provides valuable references for numerical modeling of geotechnical large-deformation problems and safety assurance in construction near operational railways.