Characterization of the Swelling Properties of Highly Plastic Clays Using Centrifuge Technology
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Technical Report Documentation Page 1. Report No. 2. Government 3. Recipient’s Catalog No. FHWA/TX-09/0-6048-1 Accession No. 4. Title and Subtitle 5. Report Date Characterization of the Swelling Properties of Highly Plastic December 2008; Revised April 2009 Clays Using Centrifuge Technology 6. Performing Organization Code 7. Author(s) 8. Performing Organization Report No. Jorge G. Zornberg, Jeffrey A. Kuhn, and Michael D. Plaisted 0-6048-1 9. Performing Organization Name and Address 10. Work Unit No. (TRAIS) Center for Transportation Research 11. Contract or Grant No. The University of Texas at Austin 0-6048 3208 Red River, Suite 200 Austin, TX 78705-2650 12. Sponsoring Agency Name and Address 13. Type of Report and Period Covered Texas Department of Transportation Technical Report Research and Technology Implementation Office 09/2007–08/2008 P.O. Box 5080 Austin, TX 78763-5080 14. Sponsoring Agency Code 15. Supplementary Notes Project performed in cooperation with the Texas Department of Transportation and the Federal Highway Administration. 16. Abstract A feasibility study was performed to determine the potential advantages of characterizing the swelling properties of highly plastic clay using a geotechnical centrifuge. This study consisted of an experimental program involving a series of tests in a small and large centrifuge in which water was ponded atop compacted clay specimens, flown up to speed, and the specimen’s height was monitored with time. This method allowed for the characterization of the swelling properties of the soil within 24 hours of the start of testing. Traditional free-swell testing to achieve the same level of characterization required approximately 30 days for the highly plastic clay evaluated in the study. This new centrifuge methodology for evaluating the swelling potential of clay was found to produce comparable results to traditional testing in a fraction of the time. Centrifuge testing of highly plastic clays will allow the Texas Department of Transportation to acquire a speedy characterization of the swelling characteristics of highly plastic clays by direct measurement of swelling rather than by the use of correlations between swelling and index properties or suction. 17. Key Words 18. Distribution Statement Highly plastic clay, swelling, and centrifugation, No restrictions. This document is available to the public through the National Technical Information Service, Springfield, Virginia 22161; www.ntis.gov. 19. Security Classif. (of report) 20. Security Classif. (of this page) 21. No. of pages 22. Price Unclassified Unclassified 82 Form DOT F 1700.7 (8-72) Reproduction of completed page authorized Characterization of the Swelling Properties of Highly Plastic Clays Using Centrifuge Technology Jorge G. Zornberg, Ph.D., P.E. Jeffrey A. Kuhn Michael D. Plaisted CTR Technical Report: 0-6048-1 Report Date: December 2008; Revised April 2009 Project: 0-6048 Project Title: Soil Testing Using Centrifuge Technology Sponsoring Agency: Texas Department of Transportation Performing Agency: Center for Transportation Research at The University of Texas at Austin Project performed in cooperation with the Texas Department of Transportation and the Federal Highway Administration. Center for Transportation Research The University of Texas at Austin 3208 Red River Austin, TX 78705 www.utexas.edu/research/ctr Copyright (c) 2008 Center for Transportation Research The University of Texas at Austin All rights reserved Printed in the United States of America iv Disclaimers Author's Disclaimer: The contents of this report reflect the views of the authors, who are responsible for the facts and the accuracy of the data presented herein. The contents do not necessarily reflect the official view or policies of the Federal Highway Administration or the Texas Department of Transportation (TxDOT). This report does not constitute a standard, specification, or regulation. Patent Disclaimer: There was no invention or discovery conceived or first actually reduced to practice in the course of or under this contract, including any art, method, process, machine manufacture, design or composition of matter, or any new useful improvement thereof, or any variety of plant, which is or may be patentable under the patent laws of the United States of America or any foreign country. Engineering Disclaimer NOT INTENDED FOR CONSTRUCTION, BIDDING, OR PERMIT PURPOSES. Project Engineer: Jorge G. Zornberg Professional Engineer License State and Number: CA No. C 056325 P. E. Designation: Research Supervisor v Acknowledgments The authors express appreciation for the dedicated guidance of the TxDOT Project Director, Dr. Zhiming Si. We are also thankful for the input by members of the PMC, including David Head, Caroline Herrera, Christopher Weber, and Stanley Yin. RTI’s support by German Claros and Frank Espinosa is much valued. vi Table of Contents Chapter 1. Introduction................................................................................................................ 1 Chapter 2. Assessment of Existing Information......................................................................... 3 2.1 TxDOT Research on Pavements over Expansive Clays ........................................................3 2.2 Conventional swelling tests on highly plastic clays ..............................................................4 2.3 The Potential Vertical Rise (PVR) Method ...........................................................................5 2.4 Potential Vertical Rise Revisited (TxDOT 0-4518) ..............................................................5 2.5 Infiltration tests on highly plastic clay in the centrifuge .......................................................7 2.6 Assessment of TxDOT needs ................................................................................................8 Chapter 3. Characterization of Eagle Ford Clay ....................................................................... 9 3.1 Index parameters ....................................................................................................................9 3.1.1 Grain size distribution .................................................................................................... 9 3.1.2 Atterberg limits .............................................................................................................. 9 3.1.3 Moisture density relationships ..................................................................................... 10 3.1.4 Specific gravity ............................................................................................................ 11 3.2 Free-swell tests ....................................................................................................................11 3.2.2 Effect of compaction water content on swelling .......................................................... 13 3.2.3 Effect of seating loads on swelling .............................................................................. 15 3.2.4 Findings from free-swell testing .................................................................................. 16 3.3 Saturated hydraulic conductivity .........................................................................................16 3.4 Summary of characterization of Eagle Ford Clay ...............................................................17 Chapter 4. Small Centrifuge Equipment and Procedure ........................................................ 19 4.1 Introduction ..........................................................................................................................19 4.2 Small Centrifuge Setup ........................................................................................................20 4.2.1 Centrifuge Cup ............................................................................................................. 20 4.2.2 Permeameter Cup ......................................................................................................... 20 4.2.3 Porous Supporting Plate ............................................................................................... 21 4.2.4 Permeameter Cap ......................................................................................................... 22 4.3 Small Centrifuge Testing Procedure ....................................................................................22 4.4 Small Centrifuge Typical Result and Repeatability ............................................................23 Chapter 5. Large Centrifuge Equipment and Procedure ....................................................... 25 5.1 Large Centrifuge Setup ........................................................................................................25 5.1.1 General Setup ............................................................................................................... 25 5.1.2 Permeameter Cup ......................................................................................................... 28 5.1.3 Permeameter Outflow Plate ......................................................................................... 29 5.1.4 Permeameter Cap and linear displacement transducer ................................................ 29 5.1.5 In-flight addition of water ............................................................................................ 30 5.1.6 Overview of the system ............................................................................................... 31 5.2 Large