The lateral behaviour of offshore piles is often predicted with the p-y method described in API RP 2GEO. As most semi-empirical methods, the API p-y methodology has some inherent bias related to the database initially used to calibrate the method. A known bias, particularly studied in recent years by the offshore wind industry is a potential inaccuracy for the design of large diameter piles. This paper presents a case study of a lateral pile load test in medium dense to dense sand. A single pile was tested as part of a port development project, which required the use of 1.8m to 2.5m diameter dolphin piles. Uncertainties remained at the end of detailed design, with respect to the accuracy of the predicted lateral pile load-displacement behaviour, and led to a decision, by the project team, to undertake a full scale lateral test of one of the dolphin piles. The tested pile had an external diameter, D, of 1.8m, with an embedment, L, of approximately 21m and stick-up of approximately 19m (of which 15m were under water). The pile was tested by applying an unfactored design SLS load of 1452kN two meters below pile top. The load was applied through reaction with a nearby 2.2m diameter pile. The ground conditions at the site predominantly comprised interbedded horizontal bedded medium dense to dense sands. This paper provides the details of the pile, lateral pile test procedure, load test results and a comparison of the observed load-deflection with predictions made with the API method. Post test residual displacements are also discussed. Conclusions and recommendations are given with regards to the applicability of the API p-y methodology to predict such pile load-displacement in medium dense to dense sand.
Mathieu Guinard, David P. Waring, Subra Padmanabhan and Marisa S. Soares
Keywords: pile load test, p-y curves, lateral response, sand
Publisher: DFI