Pile-Driving Formulas for Friction Piles in Sand

by Roy E. Olson, (M.ASCE), Professor of Civil Engineering; University of Illinois, Urbana, IL,
Kaare S. Flaate, (A.M.ASCE), Chief Engineer; Norwegian Road Research Lab., Oslo,



Abstract: Dynamic pile-driving formulas are widely used in predicting the load-carrying capacity of friction piles and in writing pile-driving specifications. Further, when load tests are available, dynamic pile-driving formulas are used to interpolate between, or extrapolate beyond, the load test results. The accuracy of a pile-driving formula can be checked by comparing calculated pile capacities with capacities measured in the field. Such comparisons have demonstrated that the formulas do not generally apply to cohesive soils, especially soft cohesive soils, and do not apply to piles acting as groups. They apply most accurately to individual piles driven into cohesion-less soils. It has also been demonstrated that few, if any, of the existing dynamic pile-driving formulas are theoretically valid. Most of the formulas were derived either using oversimplified assumptions or using empirical parameters that could be adjusted to bring the predicted capacities approximately into conformance with field measurements. In addition to the theoretical errors, there are errors in many of the field measurements because of friction in the rams of hydraulic jacks or improper calibration of equipment. In addition, random variations in the measured capacity occur because of the problem of uniquely defining failure in the field. Thus, correlations between predicted pile capacities and capacities measured in the field are likely to involve considerable scatter.

Subject Headings: Pile driving | Dynamic loads | Piles | Load tests | Friction | Load bearing capacity | Dynamic tests | Pile tests

 

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