Evaluation of API and CPT Axial Pile Capacity Methods of Campeche Bay Soils for the Design of Offshore Piles-Paper

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The study compares conventional API-11 axial pile capacity estimates with four CPT-based methods—ICP-05, NGI-05, Fugro-11/05, and UWA-05—for open-ended driven steel piles in the Bay of Campeche. Analyses covered 39 offshore sites, grouped by predominant soil profile, and pile diameters from 36 to 84 inches. In total, 1,665 capacity curves were generated using interpreted CPT and other geotechnical data.<br /><br />In clay profiles, the CPT-based methods generally produced capacities similar to API-11 down to about 50 m. At greater depths, API-11 and NGI-05 tended to predict higher capacities than ICP-05 and Fugro-11/05. In sand and mixed profiles, API-11 and NGI-05 usually formed the higher-capacity group, while ICP-05, Fugro-11/05, and UWA-05 generally predicted lower values. ICP-05 showed comparatively stable results in stratified soils, whereas some methods were more erratic in sand and mixed profiles. Increasing pile diameter had a more noticeable effect on capacity ratios in sand than in clay.<br /><br />Beyond 25 m depth, CPT-based estimates were generally within about 0.8 to 1.2 times the API-11 estimate. Larger differences at shallower depths were attributed to uncertainty in shallow-soil resistance measurements. The authors note that pile load-test data for the region are limited, so API-11 serves as a reference rather than a verified benchmark. The results provide a comparative basis for reassessing offshore pile foundations, but do not establish which method is most accurate.

Keywords

API-11

CPT-based methods

axial pile capacity

offshore piles

Bay of Campeche

open-ended driven steel piles

ICP-05

NGI-05

Fugro-11/05

UWA-05