Learning from collapse of piles in liquefiable soils

Piled structures continue to fail during earthquakes despite being designed with the required safety factor against bending due to lateral loads. This paper suggests that the reason for this may be that when the ground liquefies, its reduction in lateral support allows piles to buckle under their axial load. The mechanism could have led to the collapse of many pile-supported structures in earthquakes worldwide and is likely to cause more damage in the future. The paper concludes that the practical implications could be far-reaching, requiring reassessment of existing structures in liquefiable soils as well as rewriting seismic design codes to take better account of the effects of axial load.