Effect of the combined action of lateral load and axial load on the pile instability in liquefiable soils

Even with modern design guidelines, collapse of pile-supported structures in liquefiable deposits are still observed after strong earthquakes, and buckling instability of piles has been cited as a possible mechanism of failure in liquefiable soils. However, the buckling failure of pile under the combined action of lateral load and axial load has received little attention. This paper presents a shake-table test to study the failure mechanism of an end-bearing pile partly embedded in a saturated sand layer. It is found that pile with a large mass at the top failed in buckling after the soil fully liquefied. In addition, a pseudo-static analysis method is proposed to evaluate the buckling instability of the pile under the combination of lateral and axial load. The buckling load of the pile was found to decrease with the increase in lateral inertial load. It is hence important for the designers to consider the level of lateral loading during buckling analysis of pile in liquefiable ground. Finally, a possible boundary for safe design is proposed to avoid buckling failure of the pile while considering the effect of inertial load.