SYMPOSIA PAPER Published: 29 July 2019
STP161120180015

Signal Matching Application To Nonuniform Deep Foundations

Source

Dynamic pile testing allows examination of the capacity and integrity of deep foundations. The analysis of stress wave propagation in piles is based on the application of the one-dimensional wave equation (1D WE) for either matching measured to calculated signals (e.g., CAPWAP) or to analyze modeled impact conditions (e.g., GRLWEAP). The 1D WE, a simplified formulation of three-dimensional (3D) wave propagation for uniform, slender elastic rods, is relevant to most driven piles. Drilled foundations are often irregular in shape. The dynamic test interpretation for nonuniform piles remains therefore a challenge. Drop weight dynamic load tests were used in Tema Port, Ghana, Africa, for the design, construction, and quality control of offshore foundations for a cement unloading pier. The unique foundations consist of 812.8 mm outer diameter steel pipes that during testing are partially filled with concrete, penetrating soil and embedded in 1.1 m diameter rock-socket. Stress wave propagation simulations were conducted using the 1D WE via WEAP and CAPWAP and were compared to 3D WE using the PLAXIS finite element method (FEM) software. The nonuniformity effects on the stress propagation can be observed via the FEM. The computed resultant forces of the FEM attributed to the geotechnical capacity were overall in good agreement with the investigated 1D signal matching model. While the total pile capacity of the two models compared very well, large variations could take place in the load distributions along the foundations consequential of differing analysts and/or the underlying formulations of various numerical methods. The authors conclude that the use of FEM for resolving complex problems may be required in cases where a possible failure exists along the interfaces or within the various components comprising the nonuniform section. For such cases, the 1D WE is incapable of modeling the details of the stresses and deformations within the various pile sections.

Author Information

Paikowsky, Samuel, G.
University of Massachusetts, Dept. of Civil and Environmental Engineering, Geotechnical Engineering Research Laboratory, Lowell, MA, US GeoDynamica, Inc., Newton, MA, US
Robertson, Seth, O.
GeoDynamica, Inc., Newton, MA, US
Price: $25.00
Contact Sales
Related
Reprints and Permissions
Reprints and copyright permissions can be requested through the
Copyright Clearance Center
Details
Developed by Committee: D18
Pages: 21–47
DOI: 10.1520/STP161120180015
ISBN-EB: 978-0-8031-7668-3
ISBN-13: 978-0-8031-7667-6