LABORATORY EVALUATION OF PILES INSTALLED WITH VIBRATORY DRIVERS
This report presents the results of a large-scale laboratory study on the basic behavior of displacement piles installed with vibratory drivers compared to impact hammers and the influence of various soil and driver parameters on the behavior of piles. In order to achieve the desired goals, a model testing system consisting of a long sand column capable of simulating deep sand deposits, instrumented 4-in.-diameter closed-ended pile, vibratory driver and impact hammer was designed and built. Among the driver parameters investigated are frequency, bias mass and dynamic force (eccentric moment) and sand parameters such as grain size, relative density (65 and 90%) and in-situ effective stress (10 and 20 psi). Two uniform sands with effective grain sizes of 0.2 and 1.2 mm were selected for this study, and a total of 22 large-scale model tests were performed. The optimum frequency for the test conditions, selected based on the maximum rate of penetration, was 20 Hz and was independent of bias mass and soil conditions. Among the variables investigated, the relative density of sand had the greatest effect on the rate of penetration during vibro-driving. Penetration rate also increased with increasing bias mass and decreasing in-situ horizontal stress. Grain size had a smaller, and variable, effect on rate of penetration and on bearing capacity. Impact-driven piles in sand with 65% relative density developed 25% higher shaft resistance and 15 to 20% higher toe resistance in compression than the vibro-driven piles, but this trend was completely reversed at 90% relative density, where the vibro-driven pile exhibited better static performance than the impact-driven pile. The uplift resistance that developed along the shaft of both vibro-driven piles and impact driven piles was 75% of the corresponding resistance developed in compression. Restriking of vibro-driven piles in sand with 65% relative density produced a very small increase in compression capacity, but there was no clear trend for the relative density of 90%. A design method has been proposed to predict the bearing capacity of a vibro-driven pile from rate of penetration, power delivered to the pile head and soil conditions.
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Availability:
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Supplemental Notes:
- Appendices B through Q are contained in a separate volume, as submitted by the research agency to the sponsors. Volume 2, with the same title and authors, was prepared in December 1988 and is available for purchase by written request to the NCHRP. Distribution, posting, or copying of this PDF is strictly prohibited without written permission of the Transportation Research Board of the National Academy of Sciences. Unless otherwise indicated, all materials in this PDF are copyrighted by the National Academy of Sciences. Copyright © National Academy of Sciences. All rights reserved
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Corporate Authors:
500 Fifth Street, NW
Washington, DC United States 20001 -
Authors:
- O'Neill, M W
- Vipulanandan, C
- Publication Date: 1989-6
Media Info
- Features: Appendices; Figures; References; Tables;
- Pagination: 57 p.
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Serial:
- NCHRP Report
- Issue Number: 316
- Publisher: Transportation Research Board
- ISSN: 0077-5614
Subject/Index Terms
- TRT Terms: Alternatives analysis; Density; Design methods; Grain size; Hammers; Laboratory studies; Pile driving; Sand; Stresses
- Uncontrolled Terms: Model tests
- Old TRIS Terms: Horizontal stresses; Pile bearing capacities; Pile behavior; Vibratory drivers
- Subject Areas: Bridges and other structures; Construction; Design; Highways; I24: Design of Bridges and Retaining Walls; I53: Construction of Bridges and Retaining Walls;
Filing Info
- Accession Number: 00488706
- Record Type: Publication
- ISBN: 0-309-04613-0
- Files: TRIS, TRB, ATRI
- Created Date: Oct 31 1989 12:00AM