Large Diameter Piles Under Lateral Loading – A Database Study

Abstract

The question to be answered is: how well are current P-y curves predicting the behavior of large diameter piles subjected to monotonic lateral loading? Current P-y curves were developed about 60 years ago based on lateral load tests on piles which ranged from 0.3 to 0.6 m in diameter. Today’s pile diameters can reach 4 m or more. This significant difference in scale brings into question the applicability of these early P-y curves to today’s large diameter piles. A horizontal load tests database of 46 piles with diameters larger than 1.5 m (up to 3.0 m) and 64 piles with diameters less than 1.5 m both in sand and in clay was assembled. Predictions of load and displacement were carried out using commonly used P-y curves and the software LPILE. Within this paper, these predictions are compared to the measured loads and measured displacements. The ratio of predicted over measured quantities is plotted against pile diameter, and trends are noted. Modifications to the P-y curves are then proposed so that the ratio of predicted over measured displacement remains approximately independent of diameter. Finally, the probability that the predictions will be unsafe is evaluated.