Drivability and performance of model piles driven into cemented calcareous sand

摘要

This paper reports the results of a centrifuge model study of pile drivability in cemented calcareous sand. The tests were carried out at a scaling ratio of 1:150, on piles of equivalent prototype diameter 1.42 m, driven to depths of 20 to 24 m into cemented sand with cone resistances ranging from 14 to 60 MPa. Two samples were prepared, one with three layers of gradually increasing cone resistance, and one with a high strength intermediate layer approximately 2 pile diameters thick. Different pile toe configurations were examined ranging from open-ended (with no change of pile section near the toe) to closed-ended with a conical tip and either flush with the outer pile shaft, or slightly oversize. The effect of the different toe configurations on the drivability was examined. It was found that pile refusal occurred in the deepest (most highly cemented) layer, and that drivability became marginal for the closed-ended piles in the intermediate strong layer (in both cases, cone resistance was around 40 MPa). The hard driving was consistent with high measured static capacities of the piles, and the observed drivability was found to be consistent with results from a numerical drivability study, leading to recommended soil parameters for cemented calcareous sediments.