Safety assessment of existing piled foundatons in liquefiable soils against buckling instability

Collapse of pile-supported structures in liquefiable deposits is still observed after strong earthquakes despite the fact that large factors of safety (against bending due to lateral loads and axial capacity) are employed in their design. Currently, piles in liquefiable soils are designed as beams to avoid bending failure arising from lateral inertial and kinematic (lateral spreading) loads. Recent research suggests that part of the pile in liquefiable soils needs to be treated as unsupported structural columns to avoid buckling instability. Essentially, piles should be treated as columns carrying lateral loads. Beam bending and column buckling require different approaches in design. Designing against bending would not automatically suffice for the buckling requirements. To avoid buckling instability, there is a requirement of minimum diameter of the pile depending on the depth to which the pile may be unsupported owing to liquefaction. In addition, there is also a need to reconsider the safety of the existing piled foundations designed based on the bending mechanism. This paper discusses a method to identify the existing pilesupported structures that are vulnerable to buckling instability.