As discussed in a companion paper to this conference, Wave Equation bearing graphs, and pile driving formulas are all forms of an Energy-Capacity-Movement (ECM) relationship which are used to accept driven piles which are not specifically tested. As it is generally impractical to test every pile, all these approaches have in common that they can be applied on site in real time using very basic measurements of pile movement and observations of hammer stroke.
The Wave Equation concept provides a more realistic model of the dynamic interaction of the hammer, pile and soil. From this analysis, the relationship between Capacity and Blow Count is shown graphically as a so-called Bearing Graph. There is actually a suite of Bearing Graphs for different hammer efficiency assumptions. Bearing Graphs can be considered to provide a reference ECM relationship against which the reliability of dynamic formulas can be evaluated.
This paper is based on a parametric study using the Wave Equation program, GRLWEAP (2003). The study shows that the modified Hiley Formula, duly corrected by a Dynamic Reduction Factor (DRF) reproduces the Wave Equation-predicted capacity-blow count relationships.
This paper also demonstrates how a suite of Wave Equation bearing graphs can be reduced to a single normalized graph.
Subjects: pile acceptance, pile driving formula, GRLWEAP, PDA, DRF
Author: Julian P. Seidel, Technical Director
Publisher: DFI, EFFC