The paper presents the results and findings of instrumentation monitoring during the driving of six 54-inch open-ended steel piles and fourteen 30-inch conductors through dense to very dense sand and gravel layers at the Wiriagar Deep A platform in Berau Bay, Papua Barat, Indonesia. Monitoring of pile driving was carried out with a Pile Driving AnalyserR (PDA) which provided data such as energy transmitted into the pile, driving stresses and the estimated soil resistance to driving for each hammer blow. The transmitted energy was used to evaluate the hammer performance and to control the pile driving fatigue damage by adjusting the hammer efficiency. The driving stresses also helped to minimize non-uniform impact at the pile or conductor top, and to ensure that stresses within the pile were below the allowable limit, especially at the pile tip when driving through the gravel layers. Pile monitoring data was successfully acquired for all sections of all piles, delivering a highquality continuous dataset for all piling operations. Signal matching analyses of the data from selected blows was conducted with the CAPWAPTM software which allowed for onsite evaluation of the soil resistance to driving including the shaft friction and end bearing. Comparison of the measured vs the predicted resistance was carried out in real time. Evaluation of the instrumentation data also enabled optimisation of the re-strike programme to determine the changes in pile capacity with time. A unique dataset of driving behaviour of small diameter conductors (30-in) and larger diameter piles (54-in) in gravel is now available, enabling optimised planning of future facilities in the area. A companion paper (GalanesAlvarez et al, 2020) describes the engineering design and assurance planning for the soil conditions encountered for this platform.
Chee Peng Pua, D. S. Murthy, Radha Rao, Hugo Galanes-Alvarez, P. Jeanjean and Achmad Makmur
Keywords: piles, gravel, pile monitoring, friction fatigue, drill-out, CAPWAP, Tangguh
Publisher: DFI