surface pavement solutions for poor subgrade conditions

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  • i

    SSUURRFFAACCEE PPAAVVEEMMEENNTT SSOOLLUUTTIIOONNSS FFOORR PPOOOORR

    SSUUBBGGRRAADDEE CCOONNDDIITTIIOONNSS

    Contract No. BD-546, RPWO#4

    FINAL REPORT

    Submitted to

    The Florida Department of Transportation Research Center

    605 Suwannee Street, MS 30 Tallahassee, FL 32399

    Submitted by

    Dr. Khaled Sobhan Center for Marine Structures and Geotechnique

    Department of Civil Engineering Florida Atlantic University

    Boca Raton, FL 33431 [email protected]; 561-297-3473

    Florida Atlantic University

    January 2007

  • ii

    Disclaimer Page

    The opinions, findings and conclusions expressed in this publication are those of the authors and not necessarily those of the State of Florida Department of Transportation, or the U.S. Department of Transportation. This Report was prepared in cooperation with the State of Florida Department of Transportation and the U.S. Department of Transportation.

  • iii

    APPROXIMATE CONVERSIONS TO SI UNITS

    SYMBOL WHEN YOU KNOW MULTIPLY BY TO FIND SYMBOL

    LENGTH

    in Inches 25.4 millimeters mm

    ft Feet 0.305 meters m

    yd Yards 0.914 meters m

    mi Miles 1.61 kilometers km

    SYMBOL WHEN YOU KNOW MULTIPLY BY TO FIND SYMBOL

    AREA

    in2 Squareinches 645.2 square millimeters mm2

    ft2 Squarefeet 0.093 square meters m2

    yd2 square yard 0.836 square meters m2

    ac Acres 0.405 hectares ha

    mi2 square miles 2.59 square kilometers km2

    SYMBOL WHEN YOU KNOW MULTIPLY BY TO FIND SYMBOL

    VOLUME

    fl oz fluid ounces 29.57 milliliters mL

    gal Gallons 3.785 liters L

    ft3 cubic feet 0.028 cubic meters m3

    yd3 cubic yards 0.765 cubic meters m3

    NOTE: volumes greater than 1000 L shall be shown in m3

    SYMBOL WHEN YOU KNOW MULTIPLY BY TO FIND SYMBOL

    MASS

    oz Ounces 28.35 grams g

    lb Pounds 0.454 kilograms kg

    T short tons (2000 lb) 0.907 megagrams (or "metric ton") Mg (or "t")

    SYMBOL WHEN YOU KNOW MULTIPLY BY TO FIND SYMBOL

    TEMPERATURE (exact degrees) oF Fahrenheit 5 (F-32)/9

    or (F-32)/1.8 Celsius oC

    SYMBOL WHEN YOU KNOW MULTIPLY BY TO FIND SYMBOL

    ILLUMINATION

    fc foot-candles 10.76 lux lx

    fl foot-Lamberts 3.426 candela/m2 cd/m2

    SYMBOL WHEN YOU KNOW MULTIPLY BY TO FIND SYMBOL

    FORCE and PRESSURE or STRESS

    lbf Poundforce 4.45 newtons N

    lbf/in2 poundforce per square inch 6.89 kilopascals kPa

  • iv

    Technical Report Documentation Page

    1. Report No.

    2. Government Accession No.

    3. Recipient's Catalog No. 5. Report Date January 2007

    4. Title and Subtitle Surface Pavement Solutions for Poor Subgrade Conditions

    6. Performing Organization Code

    7. Author(s) Khaled Sobhan

    8. Performing Organization Report No. 10. Work Unit No. (TRAIS)

    9. Performing Organization Name and Address Florida Atlantic University 777 Glades Road Boca Raton, FL 33413

    11. Contract or Grant No. BD-546, RPWO#4 13. Type of Report and Period Covered Final Report July 2005 January 2007

    12. Sponsoring Agency Name and Address Florida Department of Transportation 605 Suwannee Street, MS 30 Tallahassee, FL 32399

    14. Sponsoring Agency Code

    15. Supplementary Notes

    16. Abstract The western and northern parts of Districts 4 and 6 in South Florida have shallow layers of organic and plastic soils under existing roads. These roads often exhibit large amount of cracking and distortion in a short period of time. Traditional repairs are often not practical due to high costs and extended construction time, as they require complete reconstruction of the roads with surcharge or removal of the unsuitable soils materials. The use of geosynthetic reinforcements at the base/subgrade interface are not surface solutions, as they require removal of the pavement and base. Therefore, the primary motivation behind the current study was to identify rehabilitation strategies which could be readily applied to the asphalt surface layers, and to develop design methodology based on some site-specific conditions so that the identified techniques could be used elsewhere if similar soil conditions are encountered. For that purpose, a 6-mile long Pilot Test Site was selected along the alignment of SR 15 / US 98 in northwest Palm Beach county, where severe pavement distresses were observed due to the existence of thick organic layers, and a reconstruction project was scheduled to begin in 2007. Following tasks were accomplished in this study: (i) Piezocone Penetration Tests (CPTu) with Porewater Dissipation Experiments were conducted at nine locations for rapid on-site evaluation of the strength and compressibility of Florida organic soils and peats; (ii) A concurrent laboratory consolidation and secondary compression test program were conducted to validate the field test results; (iii) The site-specific soil conditions (moisture content, organic content, thickness and unit weight of the organic layer) were expressed by an Organic Factor (Forg), which was correlated with pertinent soil properties, mechanistic pavement response parameters, and probable pavement performance; (iv) PaveTrac MT-1, GlasGrid 8501, and PetroGrid 4582 were recommended as promising asphalt reinforcing products to be incorporated in experimental pavement sections proposed at 2 different locations with different Organic Factors (Forg) in order to develop direct correlations between Forg and pavement performance, and also to facilitate relative comparisons of the candidate solutions; and (v) A conceptual design framework was developed linking laboratory/field investigations, site-specific parameters, mechanistic analysis, and transfer functions for the prediction of pavement life, so that an appropriate strategy can be adopted in future reconstruction projects. 17. Key Word Organic soil, asphalt, cracking, rutting, secondary compression, geosynthetics, test sections

    18. Distribution Statement No Restrictions

    19. Security Classif. (of this report) Unclassified

    20. Security Classif. (of this page) Unclassified

    21. No. of Pages 163

    22. Price

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

  • v

    Acknowledgements

    This research investigation was sponsored by the Florida Department of Transportation (FDOT) under a contract number BD-546-4. The leadership and technical guidance provided by the Project Manager Dr. Hesham Ali, Director of Transportation Operations (District Four), is gratefully acknowledged. Special thanks to Mr. Bruce Dietrich, Dr. Bouzid Choubane, Dr. David Horhota, Mr. Robert Bostian, Mr. David Chiu, and Mr. Michael Bienvenu for serving in the Research Panel, and providing technical inputs and recommendations which significantly contributed to this study. The laboratory investigations were conducted in the Geotechnical Testing Facility in the Department of Civil Engineering at Florida Atlantic University. Mr. Kristopher Riedy and Mr. Hieu Huynh worked as Graduate Research Assistants on the project. Time and resources provided by the FDOT State Materials Office (SMO) for performing the Cone Penetration Testing and soil sampling at the project test site in Palm Beach County is deeply appreciated.

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    EXECUTIVE SUMMARY

    The western and northern parts of FDOT Districts 4 and 6 in southeast Florida contains problematic organic silts and Peats at relatively shallow depths under existing roads, which cause recurring pavement distresses in the form of cracking, rutting, and long-term secondary settlement. Traditional repair methods such as complete reconstruction, surcharging or removal of unsuitable materials, often become impractical due to high costs and prolonged construction time associated with these strategies. Therefore, the primary motivation behind the current study was two-fold: (i) to identify rehabilitation strategies which could be readily applied to the asphalt surface layers, and (ii) to develop design methodology based on some site-specific conditions so that the identified techniques could be used elsewhere if similar soil conditions are encountered. For that purpose, a 6-mile long Pilot Test Site was selected along the alignment of SR 15 / US 98 in northwest Palm Beach County, where severe pavement distresses were observed due to the existence of thick organic layers, and a reconstruction project was scheduled to begin in 2007. To achieve these study objectives, a coordinated research approach was undertaken leading to the following specific accomplishments: (1) A comprehensive literature search and a State-of-the-Practice survey were

    conducted, and three promising asphalt reinforcement products were identified for use in the pilot field test sections along SR 15 / US 98. These products are (i) PaveTrac MT-1 steel reinforcing mesh manufactured by Bekaert Corporation; (ii) GlasGrid 8501 manufactured by Saint-Gobain Technical Fabrics; and (iii) PetroGrid 4582 manufactured by Propex Fabrics.

    (2) Piezocone Penetration Tests (CPTu) with Porewater Dissipation Experiments were

    conducted at nine field locations for rapid on-site evaluation of the strength and compressibility characteristics of Florida organic soils and peats. A concurrent laboratory consolidation test program (including secondary compression tests) was conducted to validate the field test results.

    (3) The site-specific soil conditions (moisture content, organic content, thickness and

    unit weight of the organic layer) were expressed by an Organic Factor (Forg), which was correlated with pertinent soil properties, mechanistic pavement response parameters, and probable pavemen