Determination of bearing capacity of open-ended piles in sand

The bearing capacity of open-ended piles is affected by the degree of soil plugging, which is quantified by the incremental filling ratio ~IFR!. There is not at present a design criterion for open-ended piles that explicitly considers the effect of IFR on pile load capacity. In order to investigate this effect, model pile load tests were conducted on instrumented open-ended piles using a calibration chamber. The results of these tests show that the IFR increases with increasing relative density and increasing horizontal stress. It can also be seen that the IFR increases linearly with the plug length ratio ~PLR! and can be estimated from the PLR. The unit base and shaft resistances increase with decreasing IFR. Based on the results of the model pile tests, new empirical relations for plug load capacity, annulus load capacity, and shaft load capacity of open-ended piles are proposed. The proposed relations are applied to a full-scale pile load test performed by the authors. In this load test, the pile was fully instrumented, and the IFR was continuously measured during pile driving. A comparison between predicted and measured load capacities shows that the recommended relations produce satisfactory predictions.