Effect of Liquefaction on Pile Shaft Friction Capacity

Piled foundations are commonly used worldwide, and observed failures of these foundations during earthquakes has led to active research in this area. However, the way in which piles support axial loads during earthquakes is still not fully understood. In this paper, the results from centrifuge tests are presented which consider how axial loads are carried by piles during earthquake loading. It will be shown that the piles in dry soils mobilise additional shaft friction to carry the seismically induced axial loading. However, in the case of a pile group passing through a liquefiable soil layer and founded in a dense sand layer, the pile group suffered large settlements as it loses the shaft friction in the liquefied layer and attempted to mobilise additional end bearing capacity. Further, with the post-seismic dissipation of pore pressures and the consequent settlement of the soil, the piles register significant down drag forces. This resulted in a reduction of the loads being supported as shaft friction and required further end bearing capacity to be mobilised