Revisiting Hunter and Davisson (1969)

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, 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 tests 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 concluding recommendation 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. This paper adds additional insight by reanalyzing 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".