Pile Load Capacity: Estimates and Test Results

The Michigan Pile Study (1961-1965) included a series of field loading tests on both bearing and friction piles in addition to the main investigation of pile driving hammers. A comparison was made between the measured capacity and that estimated from dynamic pile driving formulas and from soil test data from borings and laboratory tests. The objective was to determine the accuracy and reliability of these two methods of predicting supporting capacity for design. It was concluded that soil test data obtained from borings and laboratory tests following standardized procedures gave the more reliable basis for predicting design capacity. A comparison between measured capacity and predictions from soil test data was considered quite satisfactory in this investigation. Predictions from representative pile driving formulas varied widely but offered much opportunity for improvement. It was concluded that dynamic pile formulas will always be useful in controlling driving and in predicting capacity where soil test data are not available.