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EVALUATION/MODIFICATION OF IDOT FOUNDATION PILING DESIGN

AND CONSTRUCTION POLICY

Prepared By

James H Long University of Illinois at Urbana-Champaign

Joshua Hendrix

US Army Corps of Engineers

Alma Baratta HNTB

Research Report ICT-09-037

A report of the findings of

ICT-R27-24 Evaluation/Modification of IDOT Foundation Piling Design and

Construction Policy

Illinois Center for Transportation

March 2009

CIVIL ENGINEERING STUDIES Illinois Center for Transportation Series No. 09-037

UILU-ENG-2009-2008 ISSN: 0197-9191

Technical Report Documentation Page 1. Report No.

FHWA-ICT-09-037

2. Government Accession No. 3. Recipient's Catalog No.

4. Title and Subtitle

Evaluation/Modification of IDOT Foundation Piling Design and Construction Policy

5. Report Date March 2009

6. Performing Organization Code

8. Performing Organization Report N o. 7. Author(s)

James H Long, Joshua Hendrix, and Alma Baratta

ICT-09-037 UILU-ENG-2009-2008

9. Performing Organization Name and Address

Illinois Center for Transportation Department of Civil and Environmental Engineering University of Illinois at Urbana-Champaign 205 N. Mathews Ave., MC-250 Urbana, IL 61801

10. Work Unit ( TRAIS)

11. Contract or Grant No. ICT-R27-24 13. Type of Report and Period Covered

January 2007 through March 2009

12. Sponsoring Agency Name and Address

Illinois Department of Transportation Bureau of Materials and Physical Research 126 East Ash Street Springfield, IL 62704-4766

14. Sponsoring Agency Code

15. Supplementary Notes

16. Abstract

The Illinois Department of Transportation (IDOT) estimates pile lengths based on a static analysis method; however, the final length of the pile is determined with a dynamic formula based on the pile driving resistance exhibited in the field. Because different methods are used for estimating and for acceptance, there is usually a lack of agreement between the estimated length and the driven length of pile. The objective of this study is to assess the ability of the methods currently used by IDOT, to assess other methods for estimating pile capacity, to improve the methods if possible, and to determine resistance factors appropriate for the methods. This study reports pile load test data along with pile driving information and subsurface information, and uses this information to investigate and quantify the accuracy and precision with which five different static methods and five different dynamic formulae predict capacity. These static methods are the IDOT Static method, the Kinematic IDOT (K-IDOT) method, the Imperial College Pile (ICP) method, Olsons method and Driven. The dynamic formulae are the EN-IDOT formula, the FHWA-Gates Formula, the Washington State Department of Transportation (WSDOT) formula, the FHWA-UI formula, and WEAP. Three databases were assembled and used to quantify the ability of these methods to predict capacity. Results suggest that the three dynamic formulae: WS-DOT, the FHWA-Gates, and the UI-Gates provide similar accuracy. However, the WS-DOT formula is simple to implement and predicts capacity most consistently for the databases reviewed in this study. A value of 0.55 is recommended for the resistance factor for redundant piling. 17. Key Words piles, LRFD, pile capacity, dynamic formula, bearing capacity, static methods

18. Distribution Statement No restrictions. This document is available to the public through the National Technical Information Service, Springfield, Virginia 22161.

19. Security Classif. (of this report)

Unclassified

20. Security Classif. (of this page)

Unclassified

21. No. of Pages

58

22. Price

Form DOT F 1700.7 (8-72) Reproduction of completed page authorized

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ACKNOWLEDGMENT AND DISCLAIMER

This publication is based on the results of ICT- R27-24, Evaluation/Modification of IDOT Foundation Piling Design and Construction Policy. ICT-R27-24 was conducted in cooperation with the Illinois Center for Transportation; the Illinois Department of Transportation, Division of Highways; and the U.S. Department of Transportation, Federal Highway Administration.

Particular thanks are extended toward members of the Technical Review Panel for this project, and its chairperson. The members of the Technical Review Panel are given below: Mr. William Kramer (chairperson, IDOT) Mr. Riyad Wahab (IDOT) Mr. Terry McCleary (formerly IDOT) Mr. Gregory Heckel (IDOT) Mr. Doug Blades (FHWA) Mr. Mark Gawedzinski (IDOT) Mr. Gary Kowalski (IDOT) Dr. Naser Abu-Hejleh, Geotechnical Engineer Specialist with the FHWA Resource Center, provided guidance throughout the project and review comments that are greatly appreciated. The contents of this report reflect the view of the author(s), who are responsible for the facts and the accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of the Illinois Center for Transportation, the Illinois Department of Transportation, or the Federal Highway Administration. This report does not constitute a standard, specification, or regulation.

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EXECUTIVE SUMMARY Pile sizes and lengths are estimated in the office based on an understanding of the thickness of soil layers and the soil properties for each layer. However, piles are driven in the field using different criteria than are used for estimating. The field criteria used by the Illinois Department of Transportation (IDOT) is typically based on a pile dynamic formula and driving resistance measured at the end-of-driving (EOD). Using one formula for estimating the required length and a different formula for controlling the driven length inevitably results in final pile lengths different than estimated lengths. One of the main purposes of the research effort reported herein is to improve and quantify the agreement between the two methods. It is also desirable to improve the precision of each predictive method as a means to improve the agreement between the methods. Finally, it is important to quantify the level of precision for these methods to enable a selection for a resistance factor for their use in LRFD design based on relevant pile data. Accordingly, the goals of this research effort are as follows:

1. Improve the agreement between estimated pile lengths and driven pile lengths. 2. Improve and quantify several methods for determining pile capacity based on pile

driving behavior. 3. Improve and quantify several methods for determining pile capacity based on soil

properties behavior. 4. Select the combination of static and dynamic pile driving formula that provide the best

agreement (item #1) and determine resistance factors for each method.

A significant amount of pile data was reviewed, recorded, analyzed, and interpreted to address these four goals. Ideally, one collection of data would provide all the information necessary for all four tasks, but no such database currently exists. Alternatively, three databases were developed to quantify specific goals. The three databases are described below:

Database 1: The International Database - this database consisted on 132 pile load tests in which static load tests were conducted and enough information on pile driving to allow the prediction of pile capacity using a simple dynamic formula and EOD conditions. This database provided the advantage that static load tests were conducted to provide a measure of capacity, and the number of tests (132) was large enough to provide a statistically significant number of tests. This database provided the information necessary to develop resistance factors for dynamic formula. The number of load tests also allowed for the development of a new method optimized to improve the agreement between predicted capacity and capacity measured from a static load test. Database 2: The Comprehensive Database - this database consisted of a much smaller number of piles. Twenty-six static load test cases were entered into this database in which there was enough soil informat