Pile setup in sand – the "PAGE" joint industry project

The reliability of long-term axial capacity predictions for large, offshore-scale, piles is uncertain. Current databases of
static load tests include very few entries with diameters ≥ 1m, and none >2m. Also, most of the available tests were
conducted at relatively early ages after driving. The PAGE Joint Industry Project addressed this knowledge gap by
collating and analysing dynamic driving data from 25 offshore piles with 1.6 to 3.4m outside diameters and contrasting
these with dynamic re-strike tests conducted between 1h and 1 year after driving. Systematic signal matching was
performed with two independent codes that applied different soil models and the outcomes were compared with
predictions from modern CPT-based static capacity design methods. Additional supporting analyses were performed
on other piles, where static and dynamic tests had been conducted, to help assess the relationships between statically
and dynamically measured resistances. Piles with 0.3 to 3.5m outside diameters followed broadly common trends over
the first 30 days after driving, with shaft capacities approximately doubling. While smaller (<1m) diameter piles driven
at onshore/nearshore sites display marked further capacity growth, larger offshore piles showed little additional
capacity gain after 30 days. The CPT-based Unified offshore pile design method offered conservative predictions for
long-term shaft resistance, while no bias was apparent with the ICP-05 approach. An inverse relationship was identified
between long-term shaft setup and diameter, which is ascribed to enhanced dilatancy applying at the pile-sand
interface. The base capacities interpreted from dynamic analyses consistently fell far below the monotonic loading
capacities predicted by current design methods and showed no significant trend to increase over time.