What is Pile Failure for Large Diameter Open-End Piles?-Paper

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The paper examines how to define nominal resistance, or “failure,” for large-diameter open-end piles (LDOEPs) using static load tests. Although static testing is the preferred way to assess pile resistance, different failure criteria can produce different resistance values and associated displacements. The authors reviewed more than 150 full-scale LDOEP tests collected for an FHWA study and found no single criterion that works consistently across all cases.<br /><br />LDOEP load–displacement behavior depends on soil conditions, pile dimensions, and whether the pile remains unplugged or develops a soil plug. Unplugged piles, often observed in cohesive soils, may show plunging behavior after side resistance is exceeded. Piles that mobilize both side and base resistance may instead show strain hardening, with resistance increasing as displacement grows.<br /><br />The study compares the Davisson, Modified Davisson, and 5-percent-diameter displacement criteria. Statistical comparisons showed broadly similar results, but this analysis alone could not establish which criterion was most appropriate. The 10-percent-diameter criterion was excluded from further evaluation because it requires impractically large displacements for LDOEPs. Across example tests, the three selected methods sometimes gave substantially different resistance values and displacements, depending on the curve shape and test conditions.<br /><br />Pile length introduces another concern: Davisson-based methods calculate elastic compression assuming the full load reaches the pile tip. For long piles that derive significant resistance from side friction, this may overestimate compression and potentially nominal resistance.<br /><br />The authors do not recommend a single universal failure criterion. Instead, they advise applying multiple objective criteria and interpreting the results in light of the load–displacement curve, corresponding displacement, pile behavior, and superstructure requirements. Both Davisson methods may be appropriate for large-diameter foundations, but their assumptions—especially for long piles—should be considered carefully.

Keywords

large-diameter open-end piles

static load tests

nominal resistance

failure criteria

load-displacement behavior

Davisson criterion

Modified Davisson

5-percent-diameter displacement

soil plug

pile resistance