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EURIPIDES: design and testing offshore pile foundations

Over 95% of offshore oil and gas platforms are steel structures founded on driven open-ended steel pipe piles. To economize on structural costs and on installation costs the number of piles is reduced as much as possible, requiring piles with very high load bearing capacities. For clayey soils the conventional design practice API RP2A (1993) is generally adequate. For sands, this practice has significant shortcomings. The EURIPIDES project load tested life-size and comprehensively instrumented pipe piles at Eemshaven, The Netherlands.

The measured bearing capacities on the Euripides test pile in very dense sands were significantly higher than predicted using current design practice. Intensive verification of the test results confirmed the high reliability and the coherence of the measurements. For the first time a direct and near-complete image could be obtained of the pile-soil interaction on life-size scale. This showed a very high skin friction near the pile toe and lower than expected skin friction along the upper part of the pile shaft.

The Euripides test results provide a firm basis for new design criteria. The current API practice uses subjective design criteria and limit values which are not related to pile geometry, to pile and soil stiffness and to the consolidation history of the sand. Comparison with 60 pile load test data from 15 different sand sites world-wide revealed that over as well as under predictions of pile capacity to a factor of 5 occurred. These differences are attributed to the shortcomings in the API criteria. Combining new design criteria for friction with a preliminary design method on end bearing, shows great promise. Both methods are based on empirical correlations with measured objective cone penetration test data. Comparison with the 60 pile load test data revealed that the over and under predictions of pile capacity were reduced to a factor of 2.

Reported by

Fugro Engineers BV
10 Veurse Achterweg
2260 AG Leidschendam
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