DFI Journal - The Journal of the Deep Foundations Institute
Volume 20, Issue 1, August 2026
DOI: 10.37308/DFIJnl.20250707.330
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Lessons from the 2025 Mobile, AL, Prediction Survey
Article Type: Research Paper
B. H. Fellenius
Abstract
A prediction survey based on the static loading test on an 18‑inch concrete-filled, closed-toe pipe pile in Mobile, Alabama attracted 74 predictions from 92 participants across 26 countries. Participants were asked to submit pile-head loading-movement curves, assess “capacity”, and plot force distribution at an applied loading equal to their assessed “capacity”. The event proceeded in three phases: initial predictions (“First Go”), revised submissions after receipt of a reference test on a near-by similar pile (“Second Go”), and a final capacity assessment after obtaining the actual test results (“Third Go”). The submissions showed a wide scatter in predicted loading-movement curves also in the Second Go after participants amended their predictions on receiving the results of the reference test. The methods of assessing “capacity” were inconsistent, underscoring the problematic and ambiguous use of “capacity” in practice. The survey revealed that, despite advances in analytical tools, geotechnical predictions are influenced by subjective judgment, disparate definitions, and overreliance on limited data. A reevaluation of how “capacity” is treated in design standards and engineering practice is sorely needed. The survey results showed, in particular, a wide range of the submitted estimate of pile movement for applied loading.
Keywords:
prediction, loading-movement, capacity, test simulation, t-z /q-z curves, force distribution