FHWA-NHI-16-072 Site Characterization PDF
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2017
J. Erik Loehr, Ph.D.1, P.E., Alan Lutenegger2, Ph.D., P.E., Brent Rosenblad, Ph.D., P.E., 1, and Andrew Boeckmann, P.E.1
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Geotechnical Site Characterization is a technical resource for geotechnical and highway engineers. It provides guidance for planning and performing subsurface investigations, classifying soil and rock, characterizing problematic materials, interpreting measurements, identifying geotechnical hazards, and documenting results. It emphasizes the interpretation of geotechnical parameters for design and construction, and considers risk and reliability in transportation projects.
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U.S. Department of Transportation Publication No. FHWA NHI-16-072 April 2017 NHI Course No. 132031 Geotechnical Engineering Circular No.5 Geotechnical Site Characterization NOTICE The contents...
U.S. Department of Transportation Publication No. FHWA NHI-16-072 April 2017 NHI Course No. 132031 Geotechnical Engineering Circular No.5 Geotechnical Site Characterization NOTICE The contents of this report reflect the views of the authors, who are responsible for the facts and accuracy of the data presented herein. The contents do not necessarily reflect policy of the Department of Transportation. This report does not constitute a standard, specification, or regulation. The United States Government does not endorse products or manufacturers. Trade or manufacturer's names appear herein only because they are considered essential to the object of this document. Technical Report Documentation Page 1. Report No. 2. Government Accession No. 3. Recipient’s Catalog No. FHWA NHI-16-072 4. Title and Subtitle 5. Report Date GEOTECHNICAL SITE CHARACTERIZATION November 2016 GEOTECHNICAL ENGINEERING CIRCULAR NO.5 6. Performing Organization Code 7. Principal Investigator(s): See Acknowledgements for Authors and Contributors 8. Performing Organization Report No. J. Erik Loehr, Ph.D.1, P.E., Alan Lutenegger2, Ph.D., P.E., Brent Rosenblad, Ph.D., P.E., 1, and Andrew Boeckmann, P.E.1 9. Performing Organization Name and Address 10. Work Unit No. (TRAIS) Parsons Brinckerhoff, Inc. One Penn Plaza, New York, NY 10119 11. Contract or Grant No. 1 University of Missouri, Columbia, MO 65211 2 University of Massachusetts, Amherst, MA 01003 DTFH61-11-D-00047-T004 12. Sponsoring Agency Name and Address 13. Type of Report and Period Covered National Highway Institute U.S. Department of Transportation 14. Sponsoring Agency Code Federal Highway Administration, Washington, D.C. 20590 15. Supplementary Notes FHWA COR: Heather Shelsta FHWA Task Manager: Silas Nichols, P.E. FHWA Technical Reviewers: Silas Nichols, P.E. and Benjamin Rivers, PE Contractor Project Manager: C. Jeremy Hung, PE 16. Abstract Characterization of subsurface conditions is one of the most challenging yet important activities required for successful planning, design, construction, and operation of transportation infrastructure. This manual is intended to provide a technical resource for geotechnical and highway engineers responsible for planning and performing subsurface investigations so that project subsurface conditions can be characterized effectively and risks attributed to ground conditions can be identified and addressed. The manual is organized to reflect the strong emphasis on interpretation of geotechnical parameters for design and construction. It describes important considerations for planning and scoping of geotechnical investigations; means and methods for classification of soil and rock based on index property measurements; identifying and characterizing potentially problematic soil and rock types for design and construction; guidance for interpretation of soil and rock properties from field and laboratory measurements; interpretation of geotechnical design parameters from collections of individual measurements; identification and characterization of geotechnical hazards; and lastly, guidance for documenting and reporting results from geotechnical investigations. 17. Key Words 18. Distribution Statement Site characterization, subsurface investigation, geotechnical parameters, soil and rock classification, problematic soils, No restrictions. consolidation, shear strength, stress-strain and stiffness, groundwater, geotechnical report. 19. Security Classif. (of this report) 20. Security Classif. (of this page) 21. No. of Pages 22. Price UNCLASSIFIED UNCLASSIFIED Form DOT F 1700.7(8-72) Reproduction of completed page authorized A copy of the SI (Modern Metric) Conversion Factors table may be found at: http://www.fhwa.dot.gov/publications/convtabl.cfm CONVERSION FACTORS Approximate Conversions to SI Units Approximate Conversions from SI Units When you know Multiply by To find When you know Multiply by To find (a) Length inch 25.4 millimeter millimeter 0.039 inch foot 0.305 meter meter 3.28 foot yard 0.914 meter meter 1.09 yard mile 1.61 kilometer kilometer 0.621 mile (b) Area square inches 645.2 square millimeters square millimeters 0.0016 square inches square feet 0.093 square meters square meters 10.764 square feet acres 0.405 hectares hectares 2.47 acres square miles 2.59 square kilometers square kilometers 0.386 square miles (c) Volume fluid ounces 29.57 milliliters milliliters 0.034 fluid ounces gallons 3.785 liters liters 0.264 gallons cubic feet 0.028 cubic meters cubic meters 35.32 cubic feet cubic yards 0.765 cubic meters cubic meters 1.308 cubic yards (d) Mass ounces 28.35 grams grams 0.035 ounces pounds 0.454 kilograms kilograms 2.205 pounds short tons (2000 lb) 0.907 megagrams (tonne) megagrams (tonne) 1.102 short tons (2000 lb) (e) Force pound 4.448 Newton Newton 0.2248 pound (f) Pressure, Stress, Modulus of Elasticity pounds per square foot 47.88 Pascals Pascals 0.021 pounds per square foot pounds per square inch 6.895 kiloPascals kiloPascals 0.145 pounds per square inch (g) Density pounds per cubic foot 16.019 kilograms per cubic meter kilograms per cubic meter 0.0624 pounds per cubic feet (h) Temperature Fahrenheit temperature(oF) 5/9(oF- 32) Celsius temperature(oC) Celsius temperature(oC) 9/5(oC)+ 32 Fahrenheit temperature(oF) Notes: 1) The primary metric (SI) units used in civil engineering are meter (m), kilogram (kg), second(s), newton (N) and pascal (Pa=N/m2). 2) In a "soft" conversion, an English measurement is mathematically converted to its exact metric equivalent. 3) In a "hard" conversion, a new rounded metric number is created that is convenient to work with and remember. PREFACE This publication, titled “GEC5 – Geotechnical Site Characterization” is the fifth in the series of geotechnical engineering guidelines called "Geotechnical Engineering Circulars (GECs)" published by Federal Highway Administration (FHWA) covering geotechnical engineering design and construction. The document replaces the 2002 version of GEC No.5 “Evaluation of Soil and Rock Properties” (FHWA- IF-02-034) developed by GeoSyntec Consultants and authored by P.J. Sabatini, R.C. Bachus, P.W. Mayne, J.A. Schneider, and T.E. Zettler. The objective of GEC-5 is to improve site characterization practices among transportation agencies, private consultants, and contractors involved in the planning, design, construction, and operation of transportation features. It is intended to be a comprehensive and practical reference to guide planning and execution of geotechnical investigations, interpretation of the acquired measurements to develop reliable geotechnical design parameters, and identifying and characterizing geotechnical hazards. This publication is also intended to serve as the reference manual for future NHI training products addressing site characterization. The current GEC5 is considerably different from the previous version it replaces. Most notably, the current manual does not provide explicit guidance for the type and number of tests required for specific design parameters. Rather, the manual recommends characterizing important design parameters to achieve a specific level of reliability and describes methods for quantifying reliability based on available measurements. This position was adopted because the reliability of geotechnical design parameters depends on many factors and it is not possible to reduce these effects to simple rules while still consistently achieving a target reliability at reasonable cost. While the guidance provided may initially seem ambiguous and unfamiliar, readers will find that they will quickly develop judgment regarding appropriate quantities of measurements with consistent application of guidance provided in Chapters 3 and 11. Readers unfamiliar with methods for characterizing uncertainty are strongly recommended to read these chapters carefully, along with the examples provided in Appendix 2. Readers will also find that these methods can be used to assess the value of different site characterization practices, to place site characterization activities into context that is meaningful to both technical and non-technical professionals, and to facilitate effective decision making for geotechnical investigations in light of the risks and costs involved. Additional notable changes to the manual include: Changes to address load and resistance factor design (LRFD) and more explicit awareness of risk and reliability for planning, design, construction, and operation of transportation features; Explicit consideration of “direct” and “indirect” measurements of geotechnical properties; Updates to address numerous technological advancements to site characterization practice, including expanded use of remote sensing, data management systems, new and improved testing devices and methods, geophysical methods, and in situ tests, among others; Expanded and updated coverage of methods for interpreting measurements from individual field and laboratory tests; Updates to reflect changes to project delivery, most notably the expanded use of design-build and other alternative project delivery mechanisms; Addition of content on problematic soils including permafrost, pyritic/acid rock, high sulfate soils, corrosive soils, dispersive soils, and liquefiable soils; Updates to reflect use of the Geological Strength Index approach for design in rock masses; Expanded content on investigation of groundwater conditions; and Specific content for identification and characterization of geotechnical hazards. The GEC5 is not intended to provide prescriptive procedures, nor to dictate methods for collection of field or laboratory measurements. Guidance for performing specific tests and executing investigations for site characterization is available from numerous other sources, including state, federal, and international standards and procedures, as well as the AASHTO Manual on Subsurface Investigations that is currently being revised and updated to reflect changes to practice since it was last published in 1988. This publication is intended for use in conjunction with these sources. Where appropriate, standard methods for executing site characterization investigations are cited throughout the manual. ACKNOWLEDGEMENTS The authors would like to acknowledge the contributions of numerous individuals and groups who helped with preparation of this document. The authors appreciate the reviews and recommendations provided by members of the Technical Working Group for this update: Tom Badger, Formerly of Washington State DOT Carl Benson, Virginia DOT Brian Collins, FHWA Federal Lands Derrick Dasenbrock, Minnesota DOT David Horhota, Florida DOT Cyrus Parker, North Carolina DOT Additional technical review was also provided by Ray Castelli and Taehong Kim from Parsons Brinckerhoff, as well as by anonymous industry reviewers affiliated with several TRB committees and the Subsurface Characterization Committee of the Deep Foundations Institute. In addition, the Principal Investigators wish to extend their gratitude for the support provided by a number of professionals at Parsons Brinckerhoff, including Damian Okon, Kirsten Vaughn and Steve Dorneles. Assistance from Grace Jao of No Boundaries is also greatly appreciated. THIS PAGE IS LEFT INTENTIONALLY BLANK TABLE OF CONTENTS List of Figures……………………………………………………………………...……………….....….xv List of Tables……………………………………………………………………………….....…….…xxxiii Chapter 1 Introduction............................................................................................................................... 1-1 1.1 Role and Value of Site Characterization..................................................................................... 1-1 1.2 Challenges for Effective Site Characterization........................................................................... 1-2 1.3 Purpose of Circular..................................................................................................................... 1-3 1.4 Organization of Circular............................................................................................................. 1-4 Chapter 2 Objectives, Uses, and Products of Site Characterization Investigations................................... 2-1 2.1 General Objectives for Site Characterization.............................................................................. 2-1 2.2 Classes of Site Characterization investigations........................................................................... 2-3 2.2.1 Desk Studies....................................................................................................................... 2-3 2.2.2 Preliminary Investigations................................................................................................. 2-4 2.2.3 Design Investigations......................................................................................................... 2-4 2.2.4 Borrow Site Investigations................................................................................................. 2-5 2.2.5 Investigations for Performance Monitoring and Condition Assessment............................ 2-6 2.2.6 Forensic Investigations...................................................................................................... 2-7 2.2.7 Investigations for Design-Build Projects........................................................................... 2-7 2.3 Geotechnical Reporting Documents........................................................................................... 2-8 2.3.1 Field Investigation Logs..................................................................................................... 2-8 2.3.2 Geotechnical Data Reports................................................................................................. 2-8 2.3.3 Geotechnical Design Reports............................................................................................. 2-9 2.3.4 Geotechnical Baseline Reports.......................................................................................... 2-9 2.4 Benefits of Site Characterization.............................................................................................. 2-10 Chapter 3 Planning and Scoping For Site Characterization Activities...................................................... 3-1 3.1 Information Requirements for Design and Construction............................................................ 3-1 3.2 Collection and Interpretation of Existing Information................................................................ 3-3 3.2.1 Desk Study......................................................................................................................... 3-4 FHWA-NHI-16-072 Table of Contents GEC 5 – Geotechnical Site Characterization i November 2016 3.2.2 Open Source and Commercial Remote Sensing Data........................................................ 3-8 3.2.3 Historical Data................................................................................................................... 3-9 3.3 Site Reconnaissance.................................................................................................................. 3-10 3.4 Influence of Number of Measurements..................................................................................... 3-11 3.4.1 General Perspectives on Reliability of Geotechnical Design Parameters........................ 3-11 3.4.2 Statistical “Sampling” for Geotechnical Site Characterization........................................ 3-13 3.4.3 Influence of Number of Measurements on Estimates for Geotechnical Design Parameters..................................................................................... 3-15 3.4.4 Influence of Number of Measurements on Estimates of Variability and Uncertainty..... 3-19 3.4.5 Influence of Number of Measurements for Geotechnical Design.................................... 3-20 3.4.6 Application of Judgment for Establishing Appropriate Number of Measurements......... 3-24 3.5 Influence of Type of Measurements......................................................................................... 3-25 3.6 Influence of Boring, Sampling and Testing Methods............................................................... 3-29 3.7 Considerations for Time Varying Conditions........................................................................... 3-31 3.8 Selection from Among Alternative Methods of Investigation.................................................. 3-32 3.9 Considerations for Different Levels of Site Characterization................................................... 3-33 3.10 Development of Scope for Field Investigations........................................................................ 3-34 3.10.1 Developing Preliminary Scopes....................................................................................... 3-35 3.10.2 Refining Preliminary Scope............................................................................................. 3-38 3.11 Development of Scope for Laboratory and Field Testing......................................................... 3-40 3.12 Special Considerations for Alternative Contracting Methods................................................... 3-42 3.13 Communication and Execution of Site Characterization Activities.......................................... 3-43 Chapter 4 Identification and Classification of Soil and Rock.................................................................... 4-1 4.1 Objectives for Identification and Classification of Soil and Rock.............................................. 4-1 4.2 Boring and Sampling Requirements for Index Testing............................................................... 4-1 4.3 Fundamental Concepts for Identification and Classification...................................................... 4-2 4.4 Grain-Size Distribution............................................................................................................... 4-3 4.4.1 Coarse-Grained Soils......................................................................................................... 4-3 4.4.2 Fine-Grained Soils............................................................................................................. 4-5 FHWA-NHI-16-072 Table of Contents GEC 5 – Geotechnical Site Characterization ii November 2016 4.5 Grain Shape – Coarse-Grained Soils........................................................................................... 4-6 4.6 Water Content............................................................................................................................. 4-6 4.7 Unit Weight and Specific Gravity............................................................................................... 4-7 4.8 Atterberg Limits.......................................................................................................................... 4-9 4.8.1 Determining the Liquid Limit.......................................................................................... 4-11 4.8.2 Determining the Plastic Limit.......................................................................................... 4-13 4.8.3 Determining the Shrinkage Limit..................................................................................... 4-13 4.8.4 Derived Indices from Atterberg Limits............................................................................ 4-14 4.9 Activity..................................................................................................................................... 4-14 4.10 Soil Composition....................................................................................................................... 4-15 4.10.1 X-Ray Diffraction............................................................................................................ 4-15 4.10.2 Specific Surface Area....................................................................................................... 4-16 4.10.3 Cation Exchange Capacity............................................................................................... 4-17 4.10.4 Carbonate Content............................................................................................................ 4-18 4.10.5 Organic Content............................................................................................................... 4-19 4.11 Electro-Chemical Classification Tests...................................................................................... 4-19 4.12 Rock Hardness.......................................................................................................................... 4-19 4.13 Rock Abrasion........................................................................................................................... 4-20 4.14 Rock Durability......................................................................................................................... 4-20 4.15 Rock Core Measurements......................................................................................................... 4-21 4.15.1 Rock Core Recovery........................................................................................................ 4-21 4.15.2 Rock Quality Designation ( ).................................................................................... 4-22 4.15.3 Rock Fracture Frequency (FF)......................................................................................... 4-22 4.16 Classification of Soil Using Laboratory Test Measurements.................................................... 4-23 4.16.1 Unified Soil Classification System (USCS)..................................................................... 4-24 4.16.2 AASHTO System............................................................................................................. 4-26 4.16.3 Comparison Between USCS and AASHTO Soil Classification Systems........................ 4-28 4.17 Soil Identification Using In Situ Test Measurements............................................................... 4-28 4.17.1 Identification from CPT and CPTU Measurements................................................. 4-30 4.17.2 Identification from Normalized CPT and CPTU Measurements............................. 4-32 FHWA-NHI-16-072 Table of Contents GEC 5 – Geotechnical Site Characterization iii November 2016 4.17.3 Identification from Soil Behavior Type Index......................................................... 4-33 4.17.4 Additional Characterization Using CPT and CPTU Tests............................................... 4-35 4.17.5 Identifying Cemented or Unusual Soils from Seismic Cone Penetrometer (SCPT) and Seismic Piezocone (SCPTU).................................................................................... 4-35 4.17.6 Soil Identification from Dilatometer (DMT)................................................................... 4-35 4.18 Classification of Intact Rock..................................................................................................... 4-37 4.18.1 Rock Type........................................................................................................................ 4-37 4.18.2 Grain Size......................................................................................................................... 4-38 4.18.3 Weathering State.............................................................................................................. 4-38 4.18.4 Relative Rock Strength.................................................................................................... 4-41 4.18.5 Rock Color....................................................................................................................... 4-42 4.19 Characterization of soil and Rock Using Drilling Parameters.................................................. 4-43 Chapter 7 - Problematic Soil and Rock Conditions Chapter 5 Identification and Characterization of Problematic Soil And Rock.......................................... 5-1 5.1 Problematic Soil and Rock Types............................................................................................... 5-1 5.2 Collapsible Soils......................................................................................................................... 5-4 5.2.1 Occurrence of Collapsible Soils......................................................................................... 5-5 5.2.2 Indirect Identification of Collapsible Soils........................................................................ 5-6 5.2.3 Direct Characterization of Collapsible Soils...................................................................... 5-7 5.2.4 Challenges for Subsurface Exploration in Collapsible Soils........................................... 5-10 5.3 Expansive/Shrinking Soils........................................................................................................ 5-11 5.3.1 Occurrence of Expansive Soils........................................................................................ 5-12 5.3.2 Identification and Characterization of Expansive Soils Using Indirect Methods............ 5-13 5.3.3 Characterization of Swell Potential Using Direct Methods............................................. 5-17 5.3.4 Swell “Sensitivity”........................................................................................................... 5-19 5.3.5 Characterization of Shrinkage.......................................................................................... 5-20 5.3.6 Linear Shrinkage Test...................................................................................................... 5-21 5.3.7 Shrink Test....................................................................................................................... 5-22 5.4 Organic Soils............................................................................................................................. 5-22 5.4.1 Occurrence of Organic Soils............................................................................................ 5-23 FHWA-NHI-16-072 Table of Contents GEC 5 – Geotechnical Site Characterization iv November 2016 5.4.2 Identification of Organic Soils......................................................................................... 5-23 5.4.3 Challenges for Subsurface Exploration of Organic Soils and Peat.................................. 5-24 5.4.4 Shear Strength of Organic Soils and Peats....................................................................... 5-24 5.4.5 Compressibility of Organic Soils and Peats..................................................................... 5-25 5.5 Dispersive Soils......................................................................................................................... 5-27 5.5.1 Identification of Dispersive Soils Using Indirect Measurements..................................... 5-28 5.5.2 Identification of Dispersive Soils Using Direct Measurements....................................... 5-28 5.6 Liquefiable Soils....................................................................................................................... 5-30 5.6.1 Occurrence of Liquefiable Soils....................................................................................... 5-31 5.6.2 Identification of Liquefiable Soils................................................................................... 5-31 5.7 Colluvium and Talus................................................................................................................. 5-34 5.7.1 Identification of Colluvium and Talus............................................................................. 5-34 5.7.2 Challenges for Subsurface Exploration and Testing in Colluvium.................................. 5-34 5.7.3 Challenges for Subsurface Exploration and Testing in Talus.......................................... 5-35 5.7.4 Compressibility of Colluvium and Talus......................................................................... 5-36 5.7.5 Shear Strength of Colluvium and Talus........................................................................... 5-36 5.8 Degradable Rock....................................................................................................................... 5-37 5.8.1 Identification of Degradable Materials............................................................................ 5-37 5.8.2 Classification of Shale and Degradable Rock.................................................................. 5-39 5.9 Corrosive Soils.......................................................................................................................... 5-40 5.9.1 Occurrence of Corrosive Soils......................................................................................... 5-40 5.9.2 Identification of Corrosive Soils...................................................................................... 5-41 5.9.3 Classification of Corrosive Soils...................................................................................... 5-43 5.10 Cemented Sands........................................................................................................................ 5-43 5.10.1 Identification of Cemented Sands.................................................................................... 5-44 5.10.2 Challenges for Subsurface Exploration and Testing in Cemented Sands........................ 5-45 5.10.3 Interpretation of Laboratory and Field Testing Results in Cemented Sands................... 5-46 FHWA-NHI-16-072 Table of Contents GEC 5 – Geotechnical Site Characterization v November 2016 5.11 Sensitive “Quick” Clays............................................................................................................ 5-47 5.11.1 Occurrence of “Quick” Clays........................................................................................... 5-47 5.11.2 Identification of “Quick” Clays....................................................................................... 5-47 5.11.3 Challenges for Subsurface Exploration and Testing in Sensitive Clays.......................... 5-48 5.12 High Sulfate Soils..................................................................................................................... 5-49 5.12.1 Occurrence of High Sulfate Soils..................................................................................... 5-50 5.12.2 Identification of High Sulfate Soils.................................................................................. 5-50 5.13 Pyritic/Acid Rock...................................................................................................................... 5-51 5.14 Unsaturated Soils...................................................................................................................... 5-51 5.15 Permafrost................................................................................................................................. 5-54 5.15.1 Occurrence of Permafrost................................................................................................ 5-54 5.15.2 Identification of Permafrost............................................................................................. 5-54 5.15.3 Challenges with Subsurface Investigation and Testing for Permafrost........................... 5-55 Chapter 6 Measurement and Interpretation of Consolidation Properties of Soil....................................... 6-1 6.1 Fundamental Consolidation Concepts......................................................................................... 6-1 6.2 Boring and Sampling Requirements for Laboratory Consolidation Tests.................................. 6-5 6.3 Selection of Samples for Laboratory Consolidation Testing...................................................... 6-5 6.4 Effects of Sampling Disturbance................................................................................................ 6-6 6.5 Types of Laboratory Consolidation Tests................................................................................... 6-9 6.5.1 Incremental Load Consolidation Test.............................................................................. 6-10 6.5.2 Constant Rate of Strain Consolidation Test..................................................................... 6-12 6.6 Evaluation of Preconsolidation Stress from Laboratory Consolidation Tests.......................... 6-13 6.6.1 Interpretation of Preconsolidation Stress Using Casagrande Method.............................. 6-13 6.6.2 Interpretation of Preconsolidation Stress Using Strain Energy Method.......................... 6-14 6.6.3 Influence of Strain Rate and Temperature....................................................................... 6-16 6.7 Evaluation of Compression and Recompression Indices from Laboratory Consolidation Tests................................................................................................ 6-16 6.8 Tangent Modulus Method for Interpreting Consolidation Test Results.................................... 6-18 6.9 Adjustment of laboratory consolidation tests to obtain Field Consolidation Curve................. 6-20 FHWA-NHI-16-072 Table of Contents GEC 5 – Geotechnical Site Characterization vi November 2016 6.10 Evaluation of Coefficient of Consolidation from Laboratory Consolidation Tests.................. 6-22 6.10.1 Casagrande’s Log Time Method...................................................................................... 6-23 6.10.2 Taylor’s Square Root of Time Method............................................................................ 6-23 6.11 Evaluation of Coefficient of Secondary Compression From laboratory Consolidation Tests.. 6-26 6.12 Evaluation of Preconsolidation Stress from In Situ Tests......................................................... 6-27 6.12.1 CPT/CPTU....................................................................................................................... 6-28 6.12.2 DMT................................................................................................................................. 6-30 6.12.3 Field Vane Shear Test (FVT)........................................................................................... 6-31 6.12.4 Pressuremeter Test (PMT)............................................................................................... 6-32 6.12.5 Standard Penetration Test (SPT)...................................................................................... 6-35 6.13 Evaluation of Coefficient of Lateral Consolidation from In Situ Tests.................................... 6-35 6.13.1 CPTU Dissipation Tests................................................................................................... 6-36 6.13.2 DMT Dissipation Tests.................................................................................................... 6-39 6.14 Estimation of Consolidation Parameters from Index Properties............................................... 6-42 6.14.1 Compression Index and Recompression Index................................................................ 6-43 6.14.2 Coefficient of Consolidation............................................................................................ 6-45 6.14.3 Coefficient of Secondary Compression........................................................................... 6-46 6.14.4 Stress History................................................................................................................... 6-47 Chapter 7 Measurement and Interpretation of Shear Strength Properties of Soil...................................... 7-1 7.1 Uses for Shear Strength Properties in Design and Construction................................................. 7-1 7.2 Fundamental Concepts of Soil Shear Strength............................................................................ 7-1 7.2.1 Shear Strength Envelopes.................................................................................................. 7-2 7.2.2 Defining Failure................................................................................................................. 7-5 7.2.3 Measures of Shear Strength............................................................................................... 7-7 7.2.4 Drainage and Excess Pore Water Pressures....................................................................... 7-8 7.2.5 Influence of Stress Path...................................................................................................... 7-9 7.2.6 Undrained Shear Strength and Total Stress Strength Envelopes..................................... 7-12 7.2.7 Normalized Soil Behavior................................................................................................ 7-16 7.2.8 Influence of Anisotropy................................................................................................... 7-17 FHWA-NHI-16-072 Table of Contents GEC 5 – Geotechnical Site Characterization vii November 2016 7.2.9 Influence of Strain Rate................................................................................................... 7-18 7.2.10 Influence of Cyclic Loading............................................................................................. 7-20 7.3 Boring and Sampling Requirements for Laboratory Strength Tests......................................... 7-20 7.4 Evaluation of Undrained Shear Strength................................................................................... 7-21 7.4.1 Unconsolidated-Undrained Triaxial Tests....................................................................... 7-21 7.4.2 Unconfined Compression Tests....................................................................................... 7-24 7.4.3 Consolidated-Undrained Triaxial Tests........................................................................... 7-25 7.4.4 Direct Simple Shear Tests................................................................................................ 7-26 7.4.5 Effects of Sample Disturbance......................................................................................... 7-27 7.4.6 SHANSEP Procedure....................................................................................................... 7-29 7.4.7 Selection of Specimens for Measurement of Undrained Shear Strength......................... 7-32 7.4.8 Estimation of Undrained Shear Strength from Indirect Measurements........................... 7-32 7.4.9 Selection of Testing Method(s) for Undrained Shear Strength........................................ 7-42 7.5 Evaluation of Total Stress Strength Parameters for Unsaturated Soils..................................... 7-46 7.6 Evaluation of Effective Stress Strength Parameters.................................................................. 7-48 7.6.1 Consolidated-Undrained Triaxial Tests with Pore Pressure Measurements.................... 7-48 7.6.2 Consolidated-Drained Triaxial Tests............................................................................... 7-49 7.6.3 Direct Shear Tests............................................................................................................ 7-50 7.6.4 Effects of Sample Disturbance......................................................................................... 7-50 7.6.5 Selection of Samples for Measurement of Effective Stress Strength Parameters............ 7-51 7.6.6 Selection of Laboratory Testing Method......................................................................... 7-52 7.6.7 Measurement of Effective Stress Strength Parameters Using Borehole Shear Test........ 7-53 7.6.8 Estimation of Effective Stress Strength Parameters from Indirect Measurements.......... 7-53 7.6.9 Estimation of Effective Stress Strength Parameters from Empirical Correlations........... 7-57 7.7 Evaluation of Residual and Fully-Softened Shear Strength Parameters................................... 7-59 7.7.1 Direct-Residual Shear Test.............................................................................................. 7-60 7.7.2 Ring Shear Test................................................................................................................ 7-61 7.7.3 Selection of Samples for Residual Shear Strength Measurement.................................... 7-61 7.7.4 Estimation of Residual and Fully Softened Shear Strength Parameters from Empirical Correlations..................................................................................................................... 7-62 7.8 Evaluation of Shear Strength Parameters for Compacted Soils................................................ 7-64 FHWA-NHI-16-072 Table of Contents GEC 5 – Geotechnical Site Characterization viii November 2016 Chapter 8 Measurement and Interpretation of Stress-Strain and Stiffness Properties............................... 8-1 8.1 Uses for Stress-Strain and Stiffness Properties........................................................................... 8-1 8.2 General Stress-Strain Response of Soil....................................................................................... 8-3 8.3 Boring and Sampling Requirements for Measurement of Stress-Strain and Stiffness Properties 8- 6 8.4 Evaluation of Small-Strain Modulus from Stress-Wave Velocity Measurements...................... 8-6 8.4.1 Intrusive Field Methods for Stress-Wave Measurements.................................................. 8-7 8.4.2 Non-Intrusive Field Methods for Stress-wave Measurements......................................... 8-10 8.5 Laboratory Measurement of Small-Strain Modulus.................................................................. 8-13 8.5.1 Bender Elements.............................................................................................................. 8-14 8.5.2 Resonance Testing........................................................................................................... 8-14 8.5.3 Direct Measurement from Stress-Strain Curve................................................................ 8-15 8.5.4 Effects of Sample Disturbance......................................................................................... 8-15 8.6 Estimation of Small-Strain Modulus from Indirect Methods.................................................... 8-15 8.6.1 Estimation of Small-Strain Shear Modulus from Soil Index Properties.......................... 8-15 8.6.2 Estimation of Small-Strain Shear Modulus from Indirect In situ Measurements............ 8-18 8.7 Evaluation of Modulus Degradation Curves from Laboratory Measurements......................... 8-22 8.8 Estimation of Modulus Degradation from Empirical Relationships......................................... 8-23 8.9 Modulus Values at Intermediate Strain Levels for Settlement Analysis................................... 8-24 8.9.1 Simple Estimates for Equivalent Modulus....................................................................... 8-25 8.9.2 Equivalent Modulus Using Modulus Degradation........................................................... 8-25 8.9.3 Pressuremeter Modulus.................................................................................................... 8-27 8.9.4 Dilatometer Modulus....................................................................................................... 8-28 8.10 Other Soil Stiffness Properties.................................................................................................. 8-29 8.10.1 Coefficient of Subgrade Reaction.................................................................................... 8-29 8.10.2 - Curves....................................................................................................................... 8-30 FHWA-NHI-16-072 Table of Contents GEC 5 – Geotechnical Site Characterization ix November 2016 Chapter 9 Measurement and Interpretation of Rock Properties................................................................. 9-1 9.1 Uses for Rock Properties in Design and Construction................................................................ 9-1 9.2 Fundamental Concepts in Rock Behavior................................................................................... 9-2 9.3 Boring and Sampling Requirements for Characterization of Intact Rock and Rock Masses...... 9-6 9.4 Measurement and Interpretation of Intact Rock Properties........................................................ 9-7 9.4.1 Uniaxial Compressive Strength.......................................................................................... 9-7 9.4.2 Shear Strength of Intact Rock............................................................................................ 9-9 9.4.3 Tensile Strength of Intact Rock........................................................................................ 9-11 9.4.4 Intact Rock Modulus........................................................................................................ 9-12 9.4.5 Evaluation of Intact Rock Properties from Indirect Measurements................................. 9-15 9.4.6 Selection of Specimens for Measurement of Intact Rock Properties............................... 9-23 9.4.7 Special Considerations for Degradable Rock................................................................... 9-23 9.5 Characterization of Discontinuities in Rock............................................................................. 9-24 9.5.1 Representation of Discontinuity Orientation.................................................................... 9-24 9.5.2 Characterization of Discontinuities from Borehole and Rock Core Measurements........ 9-25 9.5.3 Characterization of Discontinuities from Mapping of Rock Exposures.......................... 9-27 9.5.4 Shear Strength of Rock Discontinuities........................................................................... 9-29 9.5.5 Surface Roughness........................................................................................................... 9-30 9.5.6 Discontinuity Infilling...................................................................................................... 9-32 9.6 Rock Mass Classification.......................................................................................................... 9-32 9.6.1 Alternative Rock Mass Classification Systems................................................................ 9-33 9.6.2 Rock Mass Rating ( ) Classification System............................................................ 9-33 9.6.3 Geological Strength Index ( ) Classification System.................................................. 9-34 9.7 Evaluation of Rock Mass Modulus........................................................................................... 9-37 9.7.1 Evaluation of Rock Mass Modulus from in situ Test Measurements.............................. 9-38 9.7.2 Estimation of Rock Mass Modulus from................................................................ 9-46 9.7.3 Estimation of Rock Mass Modulus from Rock Mass Rating........................................... 9-47 9.7.4 Estimation of Rock Mass Modulus from Geological Strength Index.............................. 9-48 9.8 Evaluation of Shear Strength of Rock Masses.......................................................................... 9-50 FHWA-NHI-16-072 Table of Contents GEC 5 – Geotechnical Site Characterization x November 2016 Chapter 10 Measurement and Interpretation of Groundwater Conditions and Hydraulic Properties of Soil and Rock.............................................................................................. 10-1 10.1 Uses for Hydraulic Properties and Groundwater Conditions for Design and Construction...... 10-1 10.2 Fundamental Concepts of Seepage through Soil and Rock...................................................... 10-2 10.2.1 Temporal Changes in Pore Water Pressures and Water Levels....................................... 10-3 10.2.2 Water Flow and Hydraulic Conductivity......................................................................... 10-4 10.2.3 Fundamental Means for Measurement of Hydraulic Conductivity.................................. 10-5 10.3 Boring and Sampling Requirements......................................................................................... 10-7 10.4 Evaluation of Groundwater Conditions from Observations During Drilling............................ 10-8 10.5 Investigation of Groundwater Conditions Using Monitoring Wells......................................... 10-8 10.6 Investigation of Groundwater Conditions Using Piezometers................................................ 10-10 10.6.1 Standpipe Piezometers................................................................................................... 10-12 10.6.2 Twin-tube Hydraulic Piezometers.................................................................................. 10-15 10.6.3 Pneumatic Piezometers.................................................................................................. 10-16 10.6.4 Strain Gage Piezometers................................................................................................ 10-17 10.6.5 Installation of Piezometer Elements............................................................................... 10-17 10.7 Evaluation of Groundwater Conditions Using In situ Test Measurements............................. 10-19 10.8 Evaluation of Groundwater Conditions Using Geophysical Measurements........................... 10-22 10.8.1 Location of Groundwater Surface.................................................................................. 10-22 10.8.2 Investigation of Groundwater Flow............................................................................... 10-23 10.9 Methods for Evaluating Hydraulic Conductivity of Soil and Rock........................................ 10-24 10.10 Factors Affecting Hydraulic Conductivity from Laboratory Tests......................................... 10-25 10.10.1 Size of Test Specimens.................................................................................................. 10-25 10.10.2 Stress Level.................................................................................................................... 10-26 10.10.3 Sample Disturbance....................................................................................................... 10-26 10.10.4 Hydraulic Gradient......................................................................................................... 10-26 10.10.5 Permeant......................................................................................................................... 10-27 10.10.6 Temperature................................................................................................................... 10-27 10.10.7 Anisotropy of Hydraulic Conductivity........................................................................... 10-27 FHWA-NHI-16-072 Table of Contents GEC 5 – Geotechnical Site Characterization xi November 2016 10.11 Evaluation of Hydraulic Conductivity Using Laboratory Tests.............................................. 10-29 10.11.1 One-dimensional Consolidation Tests........................................................................... 10-30 10.11.2 Thin-Wall Shelby Tube Permeameters.......................................................................... 10-31 10.11.3 Compaction Mold Permeameters................................................................................... 10-32 10.11.4 Double-Ring Compaction Mold Permeameters............................................................. 10-33 10.11.5 Oversized Rigid-Wall Permeameter.............................................................................. 10-34 10.11.6 Variable Vertical Stress Rigid-Wall Permeameter......................................................... 10-34 10.11.7 Flexible-Wall Permeameters.......................................................................................... 10-34 10.12 Evaluation of Hydraulic Conductivity from Borehole Measurements.................................... 10-35 10.12.1 Auger Hole Method....................................................................................................... 10-36 10.12.2 Open End Pumping Tests............................................................................................... 10-37 10.12.3 Slug/Bail Tests in Standpipe Piezometers...................................................................... 10-38 10.12.4 Packer Pumping Tests.................................................................................................... 10-40 10.12.5 Guelph Permeameter...................................................................................................... 10-41 10.12.6 Boutwell Two-Stage Permeameter................................................................................ 10-43 10.12.7 Self-Boring (Reaming) Permeameter............................................................................. 10-45 10.12.8 Field Pumping Tests....................................................................................................... 10-46 10.13 Evaluation of Hydraulic conductivity Using Infiltrometer Methods...................................... 10-47 10.13.1 Open Single-Ring Infiltrometer..................................................................................... 10-48 10.13.2 Sealed Single-Ring Infiltrometer................................................................................... 10-49 10.13.3 Open Double-Ring Infiltrometer.................................................................................... 10-50 10.13.4 Sealed Double-Ring Infiltrometer.................................................................................. 10-50 10.13.5 Air Entry Permeameter.................................................................................................. 10-51 10.14 Evaluation of Hydraulic Conductivity Using In situ Field tests............................................. 10-52 10.14.1 Driven/Pushed Porous Probe.......................................................................................... 10-53 10.14.2 Piezocone (CPTU) Dissipation Tests............................................................................. 10-53 10.14.3 Flat Dilatometer............................................................................................................. 10-55 10.14.4 BAT Probe..................................................................................................................... 10-55 FHWA-NHI-16-072 Table of Contents GEC 5 – Geotechnical Site Characterization xii November 2016 10.15 Estimation of Hydraulic Conductivity from Correlations....................................................... 10-56 10.15.1 Estimating Hydraulic Conductivity for Granular Soils.................................................. 10-57 10.15.2 Estimating Hydraulic Conductivity for Fine-Grained Soils........................................... 10-59 Chapter 11 Development of Design Models and Selection of Design Parameters.................................. 11-1 11.1 Objectives for Interpretation of Design Parameters.................................................................. 11-1 11.2 Process for Interpretation of Design Parameters....................................................................... 11-4 11.3 Interpretation of Subsurface Stratigraphy................................................................................. 11-6 11.4 Interpretation of Design Parameters From Available measurements........................................ 11-8 11.4.1 Selection of Design Parameters from Direct Measurements........................................... 11-9 11.4.2 Estimation of Design Parameters from Indirect Measurements..................................... 11-14 11.4.3 Use of Historical Data for Establishing Design Parameters.......................................... 11-16 11.5 Calculation of Variability and Uncertainty for Design Parameters........................................ 11-17 11.5.1 Calculation of Variability and Uncertainty for Direct Measurements........................... 11-18 11.5.2 Calculation of Variability and Uncertainty for Indirect Measurements......................... 11-25 11.5.3 Calculation of Variability & Uncertainty for Combined Direct & Indirect Measurements................................................................................................... 11-29 11.6 Identifying Outliers and Resolving Inconsistencies................................................................ 11-32 11.7 Use of Observational Method................................................................................................. 11-34 11.8 Interpretation of In situ Stress State for Design...................................................................... 11-34 11.8.1 Total Vertical Stress....................................................................................................... 11-35 11.8.2 Pore Water Pressure....................................................................................................... 11-36 11.8.3 Vertical Effective Stress................................................................................................. 11-37 11.8.4 Preconsolidation Stress and Overconsolidation Ratio ( )........................................ 11-37 11.8.5 Horizontal Stresses......................................................................................................... 11-39 11.9 Interpretation of Undrained Shear Strength for Design.......................................................... 11-42 11.9.1 Interpretation of from UU Triaxial Tests and Unconfined Compression Tests........ 11-43 11.9.2 Interpretation of from Consolidated-Undrained Tests.............................................. 11-44 11.9.3 Interpretation of Undrained Shear Strength from Indirect Laboratory and Field Tests. 11-47 FHWA-NHI-16-072 Table of Contents GEC 5 – Geotechnical Site Characterization xiii November 2016 11.10 Interpretation of Total Stress Strength Parameters for Design in Unsaturated Soils.............. 11-47 11.11 Interpretation of Effective Stress Strength Parameters for Design......................................... 11-48 11.11.1 Interpretation of Effective Stress Strength Parameters from Laboratory Tests............. 11-49 11.11.2 Interpretation of Effective Stress Friction Angle from In Situ Tests............................. 11-51 11.12 Interpretation of Consolidation Parameters for Design........................................................... 11-52 11.12.1 Compressibility Parameters........................................................................................... 11-52 11.12.2 Coefficient of Consolidation.......................................................................................... 11-52 11.12.3 Coefficient of Secondary Compression......................................................................... 11-53 11.13 Evaluation of Groundwater Conditions for Design................................................................. 11-53 Chapter 12 Identification and Characterization of Geotechnical Hazards............................................... 12-1 12.1 Objectives for Identification and Characterization of Geotechnical Hazards........................... 12-1 12.2 Karst Hazards............................................................................................................................ 12-1 12.2.1 Implications of Karst Hazard for Transportation Projects............................................... 12-2 12.2.2 Identification and Characterization of Karst Hazards...................................................... 12-5 12.3 Underground Mine Hazards.................................................................................................... 12-13 12.3.1 Implications of Underground Mine Hazards for Transportation Projects...................... 12-14 12.3.2 Identification and Characterization of Underground Mine Hazards.............................. 12-14 12.4 Seismic Hazards...................................................................................................................... 12-16 12.4.1 Implications of Seismic Hazards for Transportation Projects........................................ 12-17 12.4.2 Identification and Characterization of Geotechnical Seismic Hazards.......................... 12-19 12.5 Groundwater Hazards............................................................................................................. 12-24 12.5.1 Implications of Groundwater Hazards for Transportation Projects............................... 12-25 12.5.2 Identification and Characterization of Groundwater Hazards........................................ 12-26 12.6 Landslide and Rockfall Hazards............................................................................................. 12-27 12.6.1 Implications of Landslide and Rockfall Hazards for Transportation Projects............... 12-27 12.6.2 Identification and Characterization of Landslide and Rockfall Hazards....................... 12-28 FHWA-NHI-16-072 Table of Contents GEC 5 – Geotechnical Site Characterization xiv November 2016 12.7 Landfill and Geoenvironmental Hazards................................................................................ 12-32 12.7.1 Implications of Landfill and Geoenvironmental Hazards for Transportation Projects.. 12-32 12.7.2 Identification and Characterization of Landfill and Geoenvironmental Hazards.......... 12-33 Chapter 13 Documentation, Reporting, and Communication for Site Characterization.......................... 13-1 13.1 Objectives for Documentation and Reporting of Site Characterization.................................... 13-1 13.2 Documentation and Reporting of Laboratory and Field Test Measurements........................... 13-1 13.3 Documentation and Reporting for Design Parameters.............................................................. 13-3 13.4 Geotechnical Baseline Reports................................................................................................. 13-5 13.5 General Forms of Documentation for Site Characterization..................................................... 13-6 13.5.1 Site Plans.......................................................................................................................... 13-6 13.5.2 Final Field Investigation Logs......................................................................................... 13-7 13.5.3 Laboratory Test Reports................................................................................................. 13-11 13.5.4 Design Profiles and Design Cross-sections.................................................................... 13-11 13.5.5 Observations from Field Instrumentation...................................................................... 13-16 13.6 Geotechnical Data Management Systems................................................................................. 13-1 Chapter 14 References............................................................................................................................. 14-1 LIST OF APPENDICES Appendix 1 – ASTM/AASHTO Standards Referenced............................................................................ A-1 Appendix 2 – Examples........................................................................................................................... A-2 Appendix 3 – Statistics of Geotechnical Site Characterization................................................................ A-3 FHWA-NHI-16-072 Table of Contents GEC 5 – Geotechnical Site Characterization xv November 2016 THIS PAGE IS LEFT INTENTIONALLY BLANK LIST OF FIGURES FIGURE 3-1 CORROSION-RISK RATINGS FROM THE NRCS WEB SOIL SURVEY INTERACTIVE TOOL (NRCS, 2016)...................................................................................................................................... 3-6 FIGURE 3-2 USGS TOPOGRAPHIC MAP (NRCS, 2016).............................................................................. 3-6 FIGURE 3-3 AREAS OF KNOWN DAMAGE FROM 1993 MIDWEST FLOODS (COURTESY COMMUNITY COMMONS)................................................................................................. 3-7 FIGURE 3-4 KARSTIC CONDITIONS AND LOCATIONS OF KNOWN SINKHOLES (COURTESY COMMUNITY COMMONS)................................................................................................. 3-7 FIGURE 3-5 AERIAL PHOTOGRAPH (LEFT) AND ASSOCIATED “BARE-EARTH” LIDAR IMAGE (RIGHT) OF VEGETATED AREA (FROM ANDERSON, 2013).................................................................... 3-9 FIGURE 3-6 ALTERNATIVE SAMPLES OF SIZE =4 FROM POPULATION OF SIMULATED Su MEASUREMENTS: (A) POPULATION, (B) SUBSAMPLE ONE, (C) SUBSAMPLE TWO, AND (D) SUBSAMPLE THREE............. 3-14 FIGURE 3-7 ALTERNATIVE SAMPLES OF SIZE =20 FROM POPULATION OF SIMULATED Su MEASUREMENTS: (A) POPULATION, (B) SUBSAMPLE ONE, (C) SUBSAMPLE TWO, AND (D) SUBSAMPLE THREE................ 3-14 FIGURE 3-8 HISTOGRAMS OF MEAN Su FROM SUBSAMPLES OF SIZE: (A) =5, AND (B) =20.................. 3-16 FIGURE 3-9 INTERPRETED MEAN FROM SUBSAMPLES OF DIFFERENT SIZES: (A) RELATIVELY UNIFORM SITE, AND (B) HIGHLY VARIABLE SITE (ADAPTED FROM LOEHR, ET AL., 2015)................................. 3-17 FIGURE 3-10 SIMULATED POPULATIONS OF Su MEASUREMENTS FOR: (A) RELATIVELY UNIFORM SITE AND (B) HIGHLY VARIABLE SITE................................................................................................................ 3-18 FIGURE 3-11 RANGES OF COVμsu TERMINED FROM SUBSAMPLES OF DIFFERENT SIZES FOR: (A) RELATIVELY UNIFORM SITE AND (B) HIGHLY VARIABLE SITE (ADAPTED FROM LOEHR, ET AL., 2015)............................................................................................. 3-20 FIGURE 3-12 PERCENTAGES OF SPREAD FOOTINGS THAT PRACTICALLY ACHIEVE TARGET PROBABILITY OF FAILURE WHEN DESIGNED USING AASHTO LRFD PROVISIONS FOR A RELATIVELY UNIFORM SITE: (A) “SATISFACTORY” CASES, AND (B) “UNDER-RELIABLE” AND “OVER-RELIABLE” CASES (ADAPTED FROM LOEHR, ET AL., 2015)............................................................................................. 3-22 FIGURE 3-13 PERCENTAGES OF SPREAD FOOTINGS THAT PRACTICALLY ACHIEVE TARGET PROBABILITY OF FAILURE WHEN DESIGNED USING AASHTO LRFD PROVISIONS FOR A VARIABLE SITE: (A) “SATISFACTORY” CASES, AND (B) “UNDER-RELIABLE” AND “OVER-RELIABLE” CASES, (ADAPTED FROM LOEHR, ET AL., 2015)............................................................................................. 3-22 FHWA-NHI-16-072 Table of Contents GEC 5 – Geotechnical Site Characterization xvii November 2016 FIGURE 3-14 PERCENTAGES OF SPREAD FOOTINGS THAT PRACTICALLY ACHIEVE TARGET PROBABILITY OF FAILURE WHEN DESIGNED USING MODOT LRFD PROVISIONS FOR A UNIFORM SITE: (A) “SATISFACTORY” CASES, AND (B) “UNDER-RELIABLE” AND “OVER-RELIABLE” CASES (ADAPTED FROM LOEHR, ET AL., 2015)............................................................................................. 3-23 FIGURE 3-15 EMPIRICAL TRANSFORMATION BETWEEN Is AND qu (DENOTED AS ) FROM RUSNAK AND MARK (2000)..................................................................................................................................... 3-27 FIGURE 4-1 GRAIN-SIZE DISTRIBUTION CURVES FOR TWO COARSE-GRAINED SOILS................................ 4-4 FIGURE 4-2 PARTICLE SHAPES FOR COARSE-GRAINED SOILS (FROM MITCHELL AND SOGA, 2005)......... 4-6 FIGURE 4-3 CONCEPTUAL MODEL OF ATTERBERG LIMITS (FROM CODUTO, 2001)................................ 4-10 FIGURE 4-4 IDEALIZED RELATION BETWEEN VOLUME AND WATER CONTENT OF SOIL INCLUDING ATTERBERG LIMITS........................................................................................................................... 4-10 FIGURE 4-5 EQUIPMENT USED FOR DETERMINING LIQUID LIMIT BY CASAGRANDE CUP METHOD.......... 4-11 FIGURE 4-6 FALL CONE EQUIPMENT USED FOR DETERMINING LIQUID LIMIT......................................... 4-12 FIGURE 4-7 DETERMINATION OF LIQUID LIMIT FROM FALL CONE TEST ACCORDING TO BRITISH STANDARD BS1377 (ADAPTED FROM AZADI AND MONFARED, 2012)............................................. 4-12 FIGURE 4-8 MINERALOGICAL CHARACTERIZATION OF A NATURAL CLAY: (A) NATURAL WATER CONTENT AND ATTERBERG LIMITS, (B) RELATIVE ABUNDANCE OF MINERALS FROM BULK SAMPLE, AND (C) RELATIVE ABUNDANCE OF MINERALS FROM CLAY-SIZE FRACTION.................................................. 4-16 FIGURE 4-9 GENERAL SEQUENCE FOR SITE CHARACTERIZATION........................................................... 4-23 FIGURE 4-10 SUMMARY OF MAJOR SOIL TYPES IDENTIFIED BY USCS (FROM HOLTZ ET, AL., 2011)..... 4-24 FIGURE 4-11 CASAGRANDE PLASTICITY CHART FOR CLASSIFICATION OF FINE-GRAINED SOILS (FROM ASTM D2487, 2011).............................................................................................................. 4-25 FIGURE 4-12 AASHTO SOIL CLASSIFICATIONS FOR FINE-GRAINED SOILS (FROM ASTM D3282, 2015).............................................................................................................. 4-27 FIGURE 4-13 SUBSURFACE PROFILE DERIVED FROM CPT MEASUREMENTS (FROM MAYNE, 2007)....... 4-29 FIGURE 4-14 SOIL BEHAVIOR TYPE ( ) CHARTS FOR CPT MEASUREMENTS: (A) ORIGINAL CHART FROM ROBERTSON ET AL. (1986), AND (B) UPDATED CHART FROM ROBERTSON (2010).................. 4-31 FIGURE 4-15 SOIL BEHAVIOR TYPE ( ) CHART FOR CPTU MEASUREMENTS (FROM ROBERTSON ET AL., 1986)...................................................................................................... 4-32 FIGURE 4-16 SOIL BEHAVIOR TYPE ( ) CHART FOR NORMALIZED CPT AND CPTU MEASUREMENTS (FROM ROBERTSON, 1990)................................................................................................................. 4-33 FIGURE 4-17 SOIL BEHAVIOR TYPE CHART FROM ROBERTSON (2010) WITH CONTOURS OF (FROM ROBERTSON, 2010)................................................................................................................. 4-34 FHWA-NHI-16-072 Table of Contents GEC 5 – Geotechnical Site Characterization xviii November 2016 FIGURE 4-18 USE OF SCPT TO DISTINGUISH CEMENTED FROM UNCEMENTED SOILS (FROM MAYNE ET AL., 2009)............................................................................................................. 4-36 FIGURE 4-19 APPROXIMATE RELATIONSHIP BETWEEN CPT Ic2 RW AND DMT ID (FROM ROBERTSON, 2009)................................................................................................................. 4-37 FIGURE 4-20 INSTRUMENTED DRILL RIG TO MEASURE DRILLING PARAMETERS..................................... 4-43 FIGURE 4-21 TYPICAL FINAL LOGS OF DRILLING PARAMETERS.............................................................. 4-44 FIGURE 5-1 GIBBS AND BARA (1967) CRITERION FOR COLLAPSIBLE SOILS (CASE I-COLLAPSE; CASE III- EXPANSION)......................................................................................... 5-7 FIGURE 5-2 RESULTS FROM SINGLE-OEDOMETER COLLAPSE TEST FOR SOUTHEAST IOWA LOESS........... 5-9 FIGURE 5-3 RESULTS OF DOUBLE OEDOMETER COLLAPSE TEST FOR UNDISTURBED NEBRASKA LOESS.. 5-9 FIGURE 5-4 DISTRIBUTION OF EXPANSIVE SOILS IN THE U.S. (OLIVE ET AL., 1989; FROM GEOLOGY.COM)..................................................................................... 5-12 FIGURE 5-5 COMMON CRACKING PATTERN IN LIGHTLY LOADED STRUCTURES ON EXPANSIVE SOILS... 5-13 FIGURE 5-6 CHARACTERIZATION OF SWELL POTENTIAL FROM CLAY-SIZE FRACTION AND ACTIVITY (AFTER SEED, ET AL., 1962)............................................................................................................... 5-14 FIGURE 5-7 CHARACTERIZATION OF SWELL POTENTIAL FROM CLAY-SIZE FRACTION AND PLASTICITY INDEX (AFTER VAN DER MERE, 1964)............................................................................................... 5-15 FIGURE 5-8 CHARACTERIZATION OF SWELLING SEVERITY FROM HOLTZ AND GIBBS (1956)................. 5-16 FIGURE 5-9 FINAL VOLUME FROM FREE SWELL TEST FOR KAOLINITE (LEFT) AND MONTMORILLONITE (RIGHT).............................................................................................................................................. 5-17 FIGURE 5-10 EXAMPLE MEASUREMENTS FROM ONE-DIMENSIONAL SWELL TEST ON HIGHLY PLASTIC CLAY.................................................................................................................................................. 5-18 FIGURE 5-11 RELOADING TEST ON SPECIMEN FROM FIGURE 5-10 TO DETERMINE SWELL PRESSURE.... 5-19 FIGURE 5-12 COMPARISON OF SWELL BEHAVIOR BETWEEN UNDISTURBED AND REMOLDED SOIL........ 5-20 FIGURE 5-13 IDEALIZED SHRINKAGE CURVE FOR AN INITIALLY SATURATED SOIL................................ 5-21 FIGURE 5-14 MEASURED SHRINKAGE CURVES USING SHRINKAGE LIMIT DISH AND LINEAR SHRINKAGE MOLD (FROM CERATO AND LUTENEGGER, 2006).............................................................................. 5-22 FIGURE 5-15 ONE-DIMENSIONAL CONSOLIDATION TEST MEASUREMENTS FOR PEAT FROM PITTSFIELD, MA................................................................................................................................ 5-26 FIGURE 5-16 VALUES OF NATURAL WATER CONTENT AND COMPRESSION INDEX FOR PEATS, CLAYS, AND SILTS (FROM MESRI, ET AL., 1997)............................................................................................ 5-26 FIGURE 5-17 IDENTIFICATION OF DISPERSIVE SOILS FROM TDS AND ESP (FROM SHERARD, ET AL., 1976B)....................................................................................................... 5-29 FHWA-NHI-16-072 Table of Contents GEC 5 – Geotechnical Site Characterization xix November 2016 FIGURE 5-18 SCHEMATIC OF PINHOLE TEST FOR CHARACTERIZING DISPERSIVE SOIL (FROM ASTM D4647, 2013).............................................................................................................. 5-30 FIGURE 5-19 LIQUEFACTION POTENTIAL CHARTS FOR SPT MEASUREMENTS (FROM YOUD, ET AL., 2001)............................................................................................................... 5-32 FIGURE 5-20 LIQUEFACTION POTENTIAL CHARTS FOR CPT MEASUREMENTS (FROM YOUD, ET AL., 2001)............................................................................................................... 5-33 FIGURE 5-21 LIQUEFACTION POTENTIAL CHART FOR SHEAR WAVE VELOCITY MEASUREMENTS (FROM ANDRUS AND STOKOE, 2000)................................................................................................. 5-33 FIGURE 5-22 MAP OF LARGE-SCALE OCCURRENCES OF WEAK ROCK IN THE U.S. (FROM SANTI, 2006).......................................................................................................................... 5-38 FIGURE 5-23 FRANKLIN’S SHALE RATING SYSTEM (FROM WALKINSHAW AND SANTI, 1996)................ 5-39 FIGURE 5-24 TYPICAL STRESS-STRAIN-VOLUME CHANGE RESPONSE FOR CEMENTED SANDS: (A) STRESS- STRAIN RESPONSE, AND (B) PEAK STRESS FAILURE ENVELOPES (FROM CLOUGH, ET AL., 1981)...... 5-45 FIGURE 5-25 SENSITIVITY OF MARINE CLAYS AS RELATED TO LIQUIDITY INDEX (FROM HOLTZ AND KOVACS, 1981)................................................................................................... 5-48 FIGURE 5-26 TYPICAL SOIL PROFILES IN PERMAFROST: CONTINUOUS PERMAFROST (LEFT) AND DISCONTINUOUS PERMAFROST (RIGHT) (FROM BROWN, 1970)......................................................... 5-55 FIGURE 6-1 IDEALIZED CONSOLIDATION TEST PLOTTED IN TERMS OF VOID RATIO.................................. 6-2 FIGURE 6-2 COMMON ALTERNATIVE PRESENTATIONS FOR CONSOLIDATION TESTS: (A) LOG OF EFFECTIVE VERTICAL STRESS VS. VERTICAL STRAIN, AND (B) NATURAL LOG OF EFFECTIVE VERTICAL STRESS VS. SPECIFIC VOLUME................................................................................................................................ 6-4 FIGURE 6-3 INTERPRETATION OF PRECONSOLIDATION STRESS FROM ONE-DIMENSIONAL CONSOLIDATION TESTS........................................................................................................................ 6-7 FIGURE 6-4 INFLUENCE OF SAMPLING METHOD ON CONSOLIDATION TEST RESULTS (BOZOZUK, 1970).. 6-8 FIGURE 6-5 COMPARISON OF CONSOLIDATION TESTS FOR SPECIMENS ACQUIRED FROM BLOCK SAMPLES, FIXED PISTON SAMPLES FOR BORINGS ADVANCED USING DRILLING MUD, AND FREE PISTON SAMPLES FOR BORINGS ADVANCED WITHOUT DRILLING MUD (FROM LANDON, ET AL., 2007).......................... 6-9 FIGURE 6-6 RESULTS FROM CONSOLIDATION TESTS FOR SAMPLES OF STIFF GLACIAL TILL OF VARYING QUALITY (FROM HOLTZ AND KOVACS, 1981; AFTER SODERMAN AND KIM, 1970).......................... 6-10 FIGURE 6-7 SCHEMATIC OF INCREMENTAL LOAD OEDOMETER CELL (FROM GERMAINE AND GERMAINE, 2009).............................................................................................................................. 6-11 FIGURE 6-8 MEASURED RESPONSE FROM AN INCREMENTAL LOAD CONSOLIDATION TEST.................... 6-11 FIGURE 6-9 SCHEMATIC OF CRS OEDOMETER CELL (ASTM D4186, 2012)........................................... 6-12 FIGURE 6-10 MEASURED RESPONSE FROM A CRS CONSOLIDATION TEST.............................................. 6-13 FHWA-NHI-16-072 Table of Contents GEC 5 – Geotechnical Site Characterization xx November 2016 FIGURE 6-11 ILLUSTRATION OF CASAGRANDE METHOD FOR INTERPRETING PRECONSOLIDATION STRESS.............................................................................................................. 6-14 FIGURE 6-12 ILLUSTRATION OF STRAIN-ENERGY METHOD FOR INTERPRETING PRECONSOLIDATION STRESS............................................................................................................................................... 6-15 FIGURE 6-13 INFLUENCE OF STRAIN RATE ON INTERPRETED PRECONSOLIDATION STRESS FOR SEVERAL CLAYS (SOGA AND MITCHELL, 1996)................................................................................................ 6-17 FIGURE 6-14 VARIATION IN PRECONSOLIDATION STRESS WITH TEMPERATURE FOR SEVERAL CLAYS (FROM LEROUEIL AND MARQUES, 1996)........................................................................................... 6-17 FIGURE 6-15 CONSOLIDATION TEST MEASUREMENTS PLOTTED AS STRESS VERSUS STRAIN USING: (A) LOGARITHMIC SCALE, AND (B) ARITHMETIC SCALE (ADAPTED FROM KARLSRUD AND HERNANDEZ-MARTINEZ, 2013)......................................................................................................... 6-18 FIGURE 6-16 TANGENT MODULUS VS. EFFECTIVE STRESS SHOWING ESTIMATE FOR PRECONSOLIDATION STRESS (ADAPTED FROM KARLSRUD AND HERNANDEZ-MARTINEZ, 2013)...................................... 6-19 FIGURE 6-17 SCHMERTMANN (1955) METHOD TO OBTAIN FIELD CONSOLIDATION CURVE FOR NORMALLY CONSOLIDATED SOILS (FROM HOLTZ ET AL., 2011)....................................................... 6-21 FIGURE 6-18 SCHMERTMANN (1955) METHOD TO OBTAIN FIELD CONSOLIDATION CURVE FOR OVERCONSOLIDATED SOILS (FROM HOLTZ ET AL., 2011).................................................................. 6-22 FIGURE 6-19 CASAGRANDE’S LOG TIME METHOD FOR DETERMINING THE COEFFICIENT OF CONSOLIDATION................................................................................................................................ 6-24 FIGURE 6-20 TAYLOR’S SQUARE ROOT OF TIME METHOD FOR DETERMINING THE COEFFICIENT OF CONSOLIDATION................................................................................................................................ 6-24 FIGURE 6-21 COEFFICIENTS OF CONSOLIDATION DETERMINED USING THE LOG TIME AND SQUARE ROOT TIME METHODS FOR DIFFERENT APPLIED EFFECTIVE STRESS............................................................ 6-25 FIGURE 6-22 EVALUATION OF Cα FROM TIME-DEFORMATION RESPONSE FOR IL CONSOLIDATION TEST INCREMENT........................................................................................................................................ 6-27 FIGURE 6-23 TRANSFORMATION FROM CORRECTED NET CONE TIP RESISTANCE TO PRECONSOLIDATION STRESS, OR “YIELD STRESS” (FROM MAYNE, 2014)........................................................................... 6-29 FIGURE 6-24 TRANSFORMATIONS FROM MEASURED CPTU PORE PRESSURE TO PRECONSOLIDATION STRESS FOR CLAYS: (A) TYPE 1 PIEZOCONES, AND (B) TYPE 2 PIEZOCONES (FROM MAYNE, 2007)........................................................................................................................ 6-30 FIGURE 6-25 TRANSFORMATION FROM DMT po TO PRECONSOLIDATION STRESS (FROM MAYNE, 1995)........................................................................................................................ 6-32 FIGURE 6-26 TRANSFORMATION FROM FIELD VANE SHEAR STRENGTH TO PRECONSOLIDATION STRESS (FROM MAYNE AND MITCHELL, 1988).............................................................................................. 6-33 FHWA-NHI-16-072 Table of Contents GEC 5 – Geotechnical Site Characterization xxi November 2016 FIGURE 6-27 RELATIONSHIP BETWEEN αFV AND PLASTICITY INDEX (FROM MAYNE AND MITCHELL, 1988).............................................................................................. 6-33 FIGURE 6-28 TRANSFORMATION FROM SELF-BORING PMT pL TO PRECONSOLIDATION STRESS (FROM KULHAWY AND MAYNE, 1990).............................................................................................. 6-34 FIGURE 6-29 TRANSFORMATION FROM PMT UNDRAINED SHEAR STRENGTH AND RIGIDITY INDEX TO PRECONSOLIDATION STRESS (FROM KULHAWY AND MAYNE, 1990)................................................ 6-34 FIGURE 6-30 TRANSFORMATION FROM SPT N60 TO σ'p (FROM MAYNE, 1995).................................... 6-35 FIGURE 6-31 PORE PRESSURE DISSIPATION MEASUREMENTS FROM CPTU IN SOFT, CLAYEY SILT......... 6-36 FIGURE 6-32 NORMALIZED PORE PRESSURE DISSIPATION FOR MEASUREMENTS IN FIGURE 6-31.......... 6-38 FIGURE 6-33 RELATION BETWEEN RIGIDITY INDEX AND OCR (FROM MAYNE, 2007)........................................................................................................................ 6-39 FIGURE 6-34 ROBERTSON ET AL. (1992) CHART FOR DETERMINING ch FROM t50 (FROM SCHNAID, 2009)...................................................................................................................... 6-39 FIGURE 6-35 MEASUREMENTS FROM DMTA AND DMTC DISSIPATION TESTS IN CLAY FOR TWO DIFFERENT DEPTHS............................................................................................................................ 6-40 FIGURE 6-36 CORRELATION BETWEEN PLASTICITY INDEX AND RECOMPRESSION AND COMPRESSION PARAMETERS (FROM KULHAWY AND MAYNE, 1990)....................................................................... 6-44 FIGURE 6-37 CORRELATION OF COEFFICIENT OF CONSOLIDATION TO LIQUID LIMIT (NAVFAC, 1986).............................................................................................................................. 6-46 FIGURE 6-38 TYPICAL RELATIONSHIP BETWEEN Cαε AND Cc FOR TWO CLAYS (FROM MESRI, ET AL., 1995)................................................................................................................. 6-47 FIGURE 6-39 GENERALIZED RELATIONSHIP BETWEEN PRECONSOLIDATION STRESS AND LIQUIDITY INDEX (NAVFAC, 1986).................................................................................................. 6-48 FIGURE 7-1 MOHR-COULOMB DIAGRAM SHOWING MOHR’S CIRCLES REPRESENTING FAILURE AND STABLE STATE OF STRESS.................................................................................................................... 7-2 FIGURE 7-2 MOHR-COULOMB DIAGRAM SHOWING STATES OF STRESS AT FAILURE FOR TESTS PERFORMED AT DIFFERENT EFFECTIVE CONFINING STRESS................................................................. 7-3 FIGURE 7-3 MODIFIED MOHR-COULOMB DIAGRAM SHOWING STATE OF STRESS AT FAILURE AND STABLE STATE OF STRESS.................................................................................................................... 7-4 FIGURE 7-4 MODIFIED MOHR-COULOMB DIAGRAM SHOWING SAME STATES OF STRESS AS SHOWN IN FIGURE 7-2.......................................................................................................................... 7-5 FIGURE 7-5 STRESS-STRAIN RESPONSE FOR KAOLINITE SPECIMENS SHOWING TWO ALTERNATIVE FAILURE CRITERIA: (A) NORMALLY CONSOLIDATED CONDITION AND (B) OVERCONSOLIDATED CONDITION........................................................................................................................................... 7-6 FHWA-NHI-16-072 Table of Contents GEC 5 – Geotechnical Site Characterization xxii November 2016 FIGURE 7-6 DRAINED STRESS-STRAIN BEHAVIOR SHOWING STRAIN SOFTENING RESPONSE TYPICAL OF STIFF, HEAVILY OVERCONSOLIDATED CLAYS...................................................................................... 7-7 FIGURE 7-7 MOHR’S CIRCLE AT FAILURE SHOWING ALTERNATIVE VALUES OF SHEAR STRESS USED TO DEFINE SHEAR STRENGTH.................................................................................................................... 7-8 FIGURE 7-8 MODIFIED MOHR-COULOMB DIAGRAM SHOWING DRAINED STRESS PATHS AND DRAINED SHEAR STRENGTHS FOR TRIAXIAL EXTENSION, DIRECT SIMPLE SHEAR, AND TRIAXIAL COMPRESSION TESTS.......................................................................................................................... 7-10 FIGURE 7-9 MODIFIED MOHR-COULOMB DIAGRAMS SHOWING UNDRAINED STRESS PATHS AND SHEAR STRENGTHS FOR TRIAXIAL EXTENSION, DIRECT SIMPLE SHEAR, AND TRIAXIAL COMPRESSION TESTS: (A) NORMALLY CONSOLIDATED CONDITION AND (B) OVERCONSOLIDATED CONDITION.................. 7-11 FIGURE 7-10 SHEARING MODES ALONG DIFFERENT PORTIONS OF A POTENTIAL SLIDING SURFACE FOR AN EMBANKMENT ON A SOFT FOUNDATION............................................................................................ 7-13 FIGURE 7-11 TOTAL STRESS STRENGTH ENVELOPES FOR UNSATURATED SOILS: (A) MOHR-COULOMB DIAGRAM AND (B) MODIFIED MOHR-COULOMB DIAGRAM............................................................... 7-14 FIGURE 7-12 TOTAL STRESS STRENGTH ENVELOPES FOR SATURATED SOILS (ϕ = ): (A) MOHR- COULOMB DIAGRAM AND (B) MODIFIED MOHR-COULOMB DIAGRAM.............................................. 7-15 FIGURE 7-13 STRESS-STRAIN RESPONSE FOR NORMALLY CONSOLIDATED KAOLINITE: (A) MEASURED RESPONSE, AND (B) NORMALIZED RESPONSE..................................................................................... 7-16 FIGURE 7-14 MEASURED su/σ'vc FOR KAOLINITE SPECIMENS AT DIFFERENT................................ 7-17 FIGURE 7-15 STRESS-INDUCED ANISOTROPY FOR UNDRAINED SHEAR STRENGTH OF NORMALLY CONSOLIDATED CLAYS (LADD, 1991).........................................................................................
