A New 'Unified' CPT-Based Axial Pile Capacity Design Method for Driven Piles in Sand-Paper

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The paper presents a unified cone penetration test (CPT)-based method for predicting the axial capacity of driven piles in sand. It combines and calibrates features of four existing CPT methods using a database of 71 static pile load tests in siliceous sands.<br /><br />The method estimates shaft resistance by relating local friction to CPT cone resistance and accounting for key physical effects: pile plugging and soil displacement during installation, distance from the pile tip (friction fatigue), dilation during loading, pile–sand interface friction, and loading direction. It adopts a mean interface friction angle of 29° where site-specific tests are unavailable, and reduces the shaft resistance factor for tension loading. The method also distinguishes open- and closed-ended piles.<br /><br />For base resistance, the method accounts for the pile’s effective displaced area and uses filtered CPT resistance near the pile tip. This captures the influence of soil layering and plugging; for typical full-scale offshore pipe piles, a simplified estimate is provided.<br /><br />Calibration showed that the unified method predicts the database tests more reliably than the existing API and ISO alternatives, with reduced variability in capacity estimates. The recommended shaft capacity represents conditions around two weeks after driving, the database’s median setup period.<br /><br />The method is intended for conventionally driven piles in clean, siliceous sand. Its applicability to other sand types, silty or gravelly sands, vibrated or jacked piles, and very large-diameter piles is uncertain. It does not explicitly model longer-term setup, and designers should use caution outside the conditions represented in the test database.

Keywords

cone penetration test

driven piles

sand

axial capacity

shaft resistance

base resistance

pile plugging

interface friction

offshore pipe piles

static pile load tests