DFI Journal - The Journal of the Deep Foundations Institute
Volume 19, Issue 1, April 2025
DOI: 10.37308/DFIJnl.20230424.274
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Revisiting Hunter and Davisson (1969) and Gregersen et al. (1973): Establishing residual force
Bengt H. Fellenius
Abstract
Hunter and Davisson (1969) wrote a pioneering paper that brought the presence of residual force and its consequence for pile load-transfer to the attention of the profession. The paper presented observations at the 1963 Lock and Dam 4 project of the Corps of Engineers, where, for one of the first times in the US, strain-gage instrumentation was used in static-loading tests. The tests combined results from compression (push) tests with those of subsequent tension (pull) tests and presented an innovative analysis linking the results of compression and tension test on the test piles to determine the true load-transfer of the pile. The analysis established that driven piles are left with locked-in force-distribution—residual force—and that this force affected the evaluation of records from an instrumented static loading test. While the conclusion that static loading tests should combine push and pull tests and the piles should be instrumented in order for the true load-transfer mechanism be determined was not that often followed by the profession, the paper certainly established the importance of the residual force. The findings were soon afterward confirmed by Gregersen et al. (1973) who determined the presence of residual force by actually referencing all records to a calibrated distribution of axial force before the pile was driven. This paper re-visits the original test records and results and adds additional insight by re-analyzing the original test records in terms of effective stress, as opposed to stress-independent method of the old times, and of pile movement as opposed to “capacity”.
Keywords:
precast concrete pile, H-pile, telltales, static loading tests, back-analysis, load-movement