Geotechnical Design Manual August 24, 2021 (PAGE INTENTIONALLY LEFT BLANK FOR DOUBLE-SIDED PRINTING) TABLE OF CONTENTS CHAPTER 1. INTRODUCTION ................................................................................................. 1 1.1 PURPOSE ................................................................................................................................. 1 1.2 CDOT INVOLVEMENT IN GEOTECHNICAL DESIGN PROCESS ............................................. 2 1.3 DESIGN-BUILD PROJECTS ...................................................................................................... 2 CHAPTER 2. GEOTECHNICAL STANDARDS, REFERENCES, AND SOFTWARE ..................... 3 2.1 GEOTECHNICAL STANDARDS AND ORDER OF PRECEDENCE ............................................. 3 2.2 GEOTECHNICAL REFERENCES ............................................................................................... 3 2.3 GEOTECHNICAL SOFTWARE .................................................................................................. 3 2.4 FORMS ...................................................................................................................................... 5 CHAPTER 3. GEOTECHNICAL INVESTIGATIONS ................................................................... 6 3.1 LITERATURE REVIEW ............................................................................................................. 6 3.2 FIELD RECONNAISSANCE ....................................................................................................... 6 3.3 PLANNING OF FIELD EXPLORATIONS ................................................................................... 7 3.3.1 Right-of-Way Permits ............................................................................................... 7 3.3.2 Right-of-Entry ........................................................................................................... 7 3.3.3 Environmental Clearances and Considerations ................................................... 7 3.3.4 Traffic Control Requirements ................................................................................ 8 3.3.5 Utility Locates ........................................................................................................... 8 3.3.6 Notice of Intent ........................................................................................................ 8 3.3.7 Health and Safety ..................................................................................................... 9 3.3.8 Interaction with the Public ..................................................................................... 9 3.4 SUBSURFACE EXPLORATIONS FREQUENCY AND DEPTH ................................................... 9 3.5 SUBSURFACE EXPLORATION METHODS ............................................................................. 11 3.5.1 Borings ...................................................................................................................... 11 3.5.2 Test Pits/Trenches ................................................................................................. 12 3.5.3 Borehole/Test Pit Abandonment ......................................................................... 12 3.5.4 Geophysical Surveys ............................................................................................... 13 3.5.5 Other Exploration Methods ................................................................................... 13 3.6 IN-SITU TESTING AND SAMPLING ....................................................................................... 14 3.6.1 Standard Penetration Test .................................................................................... 16 3.6.2 Modified California Sampler Penetration Test .................................................. 17 3.6.3 Thin-Walled Tube Samples ................................................................................... 17 3.6.4 Cone Penetration Testing ..................................................................................... 18 3.6.5 Rock Coring ............................................................................................................. 19 3.6.6 Other In-Situ Tests ................................................................................................. 19 3.7 GROUNDWATER OBSERVATIONS ........................................................................................ 19 3.7.1 Borings ...................................................................................................................... 20 3.7.2 Observation Wells .................................................................................................. 20 3.7.3 Automated Groundwater Monitoring .................................................................. 21 3.7.4 In-Situ Sampling and Testing of Groundwater .................................................. 21 3.8 SOIL AND ROCK CLASSIFICATION AND LOGGING ............................................................. 21 3.8.1 Soil Classification ................................................................................................... 22 i 3.8.2 Rock Classification ................................................................................................. 23 CHAPTER 4. LABORATORY TESTING ................................................................................... 24 4.1 LABORATORY TESTING REQUIREMENTS............................................................................ 24 4.2 TESTING PROCEDURES ........................................................................................................ 24 4.2.1 Index Testing ........................................................................................................... 25 4.2.2 Consolidation and Swell/Collapse Testing ......................................................... 25 4.2.3 Shear Strength Testing .......................................................................................... 26 4.2.4 Compaction Testing ............................................................................................... 26 4.3 QUALITY ASSURANCE AND QUALITY CONTROL ............................................................... 27 4.4 SAMPLE RETENTION ............................................................................................................. 27 CHAPTER 5. GEOTECHNICAL DESIGN ................................................................................. 28 5.1 BRIDGE FOUNDATIONS ........................................................................................................ 28 5.1.1 Driven Piles .............................................................................................................. 28 5.1.2 Drilled Shafts ........................................................................................................... 28 5.1.3 Lateral Loads for Deep Foundations ................................................................... 29 5.1.4 Load Testing of Deep Foundations ...................................................................... 29 5.2 FOUNDATIONS FOR SIGNS, LIGHTING, AND SIGNALS ..................................................... 30 5.3 EMBANKMENTS AND RETAINING WALLS ............................................................................ 30 5.3.1 Settlement ............................................................................................................... 30 5.3.2 Utilities .................................................................................................................... 30 5.3.3 Global Stability ....................................................................................................... 31 5.3.4 Permanent Cut Slopes ........................................................................................... 33 5.3.5 Retaining Walls ....................................................................................................... 33 5.4 FILL AND OTHER GEOTECHNICAL MATERIALS ................................................................. 33 5.5 SWELLING AND COLLAPSE-PRONE SOIL/ROCK ................................................................ 33 5.6 GEOTECHNICAL SEISMIC DESIGN ........................................................................................ 33 5.7 GEOTECHNICAL REPORTS ................................................................................................... 34 5.8 ENGINEERING GEOLOGY SHEETS ....................................................................................... 34 CHAPTER 6. CONSTRUCTION-PHASE SERVICES ................................................................. 35 6.1 ROLES AND RESPONSIBILITIES ............................................................................................ 35 6.1.1 Design-Build Projects ............................................................................................. 35 6.1.2 Record Keeping ....................................................................................................... 35 6.2 TEMPORARY SHORING AND EXCAVATIONS ....................................................................... 35 6.3 DRIVEN PILES ........................................................................................................................ 36 6.3.1 Construction Observation ..................................................................................... 36 6.3.2 Static Load Testing ...............................................................................................