Designing against pile-tip bearing capacity failure in liquefiable soil

Recent experimental data has demonstrated that piles passing through liquefiable layers and bearing in dense sands can suffer extensive settlement and bearing capacity failure during earthquakes. An analytical solution for the pile tip bearing capacity in liquefied soil is proposed and validated against centrifuge test data from instrumented end-bearing piles. In these experiments, strong sinusoidal shaking was applied to examine the reduction in load capacity at the pile tip across the full range of excess pore pressures which may be encountered. This demonstrated that the liquefied bearing capacity may be determined by knowledge of the excess pore pressure ratio at pile tip level alone. A database of full-scale load tests on instrumented piles bearing in sandy soils is then used to empirically relate the reduction in base capacity to the minimum static safety factor (SSF) to be used in design to avoid punching failure.