Role of Advanced Technology - Resolve Inherent Dichotomy in High Strain Dynamic Testing-PPT Presentation

PPT Presentation

Pdf Summary

The presentation reviews the evolution of high-strain dynamic testing (HSDT) for deep foundations, from top-only sensor methods to systems using embedded sensors at both the pile top and tip. Traditional Case Method analysis relies on simplifying assumptions, including treating soil damping as concentrated at the pile tip. Signal-matching methods use measured top data and modeled pile behavior, but their results can be subjective and may not yield a unique solution.<br /><br />The University of Florida (UF) method uses top and tip measurements to estimate total and tip capacity, deriving skin capacity by subtraction. The FDOT method instead estimates tip and skin resistance independently, using embedded data collectors (EDCs) at both locations. It applies an energy-based approach to tip resistance and a segmented wave-equation model to skin resistance.<br /><br />A central challenge in pile testing is that tip and skin resistance may reach their maximum mobilization on different blows, such as during initial driving and later restrike. The presentation argues that combining the independently determined optimum tip and skin resistances—“superposition”—provides a more representative estimate of true pile capacity than relying on total resistance from a single blow.<br /><br />A field example illustrates this approach: the optimum tip resistance occurred during end-of-initial-drive testing, while the optimum skin resistance occurred during restrike. Adding these separate values produced a capacity of 1,161 kips, compared with about 900 kips measured on a single restrike blow.<br /><br />The authors conclude that embedded sensors improve stress monitoring and pile-integrity assessment, while FDOT analysis can support independent resistance and settlement estimates. They suggest these capabilities can improve capacity assessment, design efficiency, construction quality, and the selection of separate resistance factors for tip and skin.

Keywords

high-strain dynamic testing

deep foundations

embedded sensors

pile capacity

Case Method

signal matching

tip resistance

skin resistance

FDOT method

superposition