Pile Driving Instrumentation of 54-Inch Piles in Gravels at the Wiriagar Deep Platform in Berau Bay, Indonesia-Paper

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The paper reports instrumentation and monitoring of six 54-inch foundation piles and fourteen 30-inch conductor piles driven through dense sand and gravel at the Wiriagar Deep A platform in Berau Bay, Indonesia. A Pile Driving Analyzer recorded hammer energy, pile stresses, and driving response; CAPWAP signal matching was used to estimate shaft and toe resistance and assess pile capacity.<br /><br />Monitoring provided continuous, high-quality data and supported real-time comparisons between measured and predicted soil resistance. It also helped optimize hammer settings, manage fatigue and pile-tip damage risks, and assess resistance changes during restrike tests. Driving stresses remained below allowable limits, and the foundation piles’ estimated design fatigue factor was about 14, higher than the planned minimum of 10.<br /><br />CAPWAP results showed that unit shaft resistance within the gravel layer was substantially lower than estimates from CPT-based methods and below the API-recommended value for dense gravel. Resistance in underlying sand was notably higher, indicating that gravel behaves differently from sand and that existing methods may not reliably characterize gravel density or pile capacity. Analyses also indicated friction fatigue: for most foundation piles, unit shaft resistance at a gravel-layer depth fell by about 65% after roughly 1,000 additional hammer blows.<br /><br />Restrike tests on one foundation pile found total skin friction increased from 21.8 MN at end of driving to 35.7 MN after about 30 hours and 44.3 MN after nearly 30 days, demonstrating significant capacity gain with time. A conductor drill-out trial also informed decisions about whether further drilling was necessary.<br /><br />The authors conclude that pile monitoring was valuable for safer, more efficient installation and capacity verification. They recommend further research to account for friction fatigue in gravel design methods, which could improve pile and hammer sizing and reduce installation risks.

Keywords

pile driving

foundation piles

conductor piles

CAPWAP

Pile Driving Analyzer

shaft resistance

toe resistance

dense gravel

friction fatigue

restrike tests