Sensitivity of buckling resistance to pile length and structural imperfections in submerged timber piles

This study investigates the buckling resistance of submerged timber piles, emphasising sensitivity to pile length, material stiffness and geometric imperfections. An integrated methodology combining ultrasonic non-destructive testing, non-linear finite element modelling (FEM) and classical Euler–Bernoulli theory was employed to evaluate pile stability. Results indicate that pile slenderness predominantly governs buckling capacity, with critical loads decreasing by up to 74% as pile length increases from 5.65 m to 10.25 m. Lateral displacement exhibits a non-linear S-shaped response, reflecting the transition from axial shortening to bending-dominated deformation – a behaviour not captured by classical theory due to its neglect of anisotropy, imperfections and soil–pile interactions. Geometric imperfections substantially reduce effective buckling loads, with FEM revealing lateral displacement amplifications of up to 20%. Incorporating anisotropic material properties and soil–pile interactions in FEM produced buckling load predictions ∼5% lower than classical theory, enhancing accuracy. These findings underscore the importance of imperfection-sensitive, geometry- and material-informed models for reliable assessment of submerged timber pile stability, supporting structural health monitoring and sustainable conservation of aquatic timber infrastructure.