PUBLICATION 293 GEOTECHNICAL ENGINEERING MANUAL CHAPTER 3 – SUBSURFACE EXPLORATIONS Table of Contents CHAPTER 3 – SUBSURFACE EXPLORATIONS 3.1 INTRODUCTION ................................................................................................................................. 1 3.1.1 Purpose ...................................................................................................................................... 2 3.1.2 Subsurface Characterization ..................................................................................................... 3 3.1.3 Subsurface Exploration Methods .............................................................................................. 3 3.2 TEST BORINGS.................................................................................................................................... 4 3.2.1 Planning Subsurface Exploration Program ................................................................................ 4 3.2.2 Subsurface Exploration Planning Meeting ................................................................................ 5 3.2.3 Test Boring Plan and Schedule of Proposed Borings ................................................................. 5 3.2.4 Guidelines for Establishing Number, Location, and Depth of Test Borings .............................. 6 3.2.5 Contingency Test Borings ........................................................................................................ 13 3.3 TEST PITS .......................................................................................................................................... 14 3.4 EXAMPLE PROJECTS ......................................................................................................................... 15 3.5 CONSIDERATIONS WHEN PLANNING SUBSURFACE EXPLORATION PROGRAM .............................. 16 3.5.1 Mandatory Pre-bid Meeting .................................................................................................... 16 3.5.2 Subsurface Exploration Capabilities of the Department ......................................................... 17 3.5.3 Utilities .................................................................................................................................... 17 3.5.4 Health and Safety Plan (HASP) ................................................................................................ 18 3.5.5 Maintenance and Protection of Traffic (MPT) and Time Restrictions ..................................... 19 3.5.6 Minimum Number of Required Drill Rigs and Allotted Time to Complete Work .................... 19 3.5.7 Temporary Potable Water Supply ........................................................................................... 20 3.6 TEST BORING EQUIPMENT, TOOLS AND PROCEDURES ................................................................... 20 3.6.1 Drill Rigs/Machinery ................................................................................................................ 20 3.6.2 Test Boring Advancement and Support in Soil ........................................................................ 21 3.6.2.1 Hollow-Stem Augers ........................................................................................................... 22 3.6.2.2 Drilled and Driven Steel Casing .......................................................................................... 23 3.6.2.3 Mud Rotary ......................................................................................................................... 23 3.6.2.4 Solid Stem Augers ............................................................................................................... 24 3.6.3 Test Boring Soil Sampling ........................................................................................................ 24 3.6.3.1 Spilt-Barrel Sampling and Standard Penetration Testing (SPT) .......................................... 24 i 3.6.3.2 Bulk Soil Sampling with Augers .......................................................................................... 26 3.6.3.3 Thin-Walled (Shelby) Tube Soil Sampling ........................................................................... 26 3.6.3.4 Piston Tube Sampler ........................................................................................................... 28 3.6.3.5 Denison and Pitcher Tube Samplers ................................................................................... 29 3.6.4 Rock Core Drilling and Sampling (Non-destructive Rock Core Drilling) .................................. 30 3.6.4.1 Core Barrels ........................................................................................................................ 31 3.6.4.2 Inner Core Barrels ............................................................................................................... 32 3.6.4.3 Core Bits ............................................................................................................................. 33 3.6.4.4 Concrete Core Drilling and Sampling .................................................................................. 34 3.6.5 Unsampled Rock Drilling (Destructive Rock Drilling) ............................................................... 34 3.7 TEST BORING PROCEDURES/CONSIDERATIONS .............................................................................. 36 3.7.1 Continuous versus Interval Standard Penetration Testing ..................................................... 36 3.7.2 Standard Penetration Test (SPT) Refusal ................................................................................ 36 3.7.3 Rock Core Drilling Core Run Lengths ....................................................................................... 37 3.7.4 Sampling Highly Weathered/Very Soft Bedrock ..................................................................... 38 3.7.5 Sampling Pinnacled and/or Voided Bedrock ........................................................................... 38 3.7.6 Inclined Drilling ........................................................................................................................ 39 3.7.7 Grouting/Backfilling Boreholes ............................................................................................... 40 3.7.8 Groundwater ........................................................................................................................... 41 3.7.8.1 Groundwater Monitoring during Subsurface Exploration.................................................. 41 3.7.8.2 Long-Term Groundwater Monitoring ................................................................................. 43 3.7.8.3 Confined and Unconfined Aquifers .................................................................................... 43 3.7.8.4 Artesian Aquifers ................................................................................................................ 43 3.7.9 Running Sands ......................................................................................................................... 44 3.7.10 Pavement Design Borings ........................................................................................................ 45 FUTURE DEVELOPMENT: CHAPTER 4 - LABORATORY TESTING CHAPTER 5 - SOIL AND ROCK PARAMETER SELECTION CHAPTER 6 - SOIL SLOPE STABILITY CHAPTER 7 - SETTLEMENT ROCK CUT SLOPE DESIGN ROCK MASS RATING (RMR) GUIDANCE ii ROCK SLAKE DURABILITY ACID BEARING ROCK COMPACTION INSTRUMENTATION FIELD (IN-SITU) TESTING IMPERVIOUS LINERS - GEOMEMBRANES AND GEOSYNTHETIC CLAY LINERS GEOSYNTHETIC REINFORCED SOIL SLOPES GEOTEXTILE USE GUIDELINES GEOCELL GEOFOAM COMPACTION GROUTING DESIGN/CONSTRUCTION IN KARST GROUND MODIFICATION SUBSIDENCE iii PUBLICATION 293 – GEOTECHNICAL ENGINEERING MANUAL CHAPTER 3 – SUBSURFACE EXPLORATIONS 3.1 INTRODUCTION This section of the publication provides guidelines, recommendations, and considerations for planning and executing subsurface exploration programs. Included are minimum requirements for number, location, and depth of test borings depending upon the complexity of the planned construction, the complexity and severity of the geologic conditions, and the risks and costs associated with system failure and/or service interruption. This section also discusses drilling equipment, tools, procedures, and other topics associated with subsurface explorations not addressed in Publication 222. The subsurface exploration program is one of the most important geotechnical tasks for the majority of projects. A properly planned and executed exploration program will provide the information needed to perform geotechnical analyses and develop geotechnical design recommendations. Consider that all transportation facilities and related assets are constructed on earth materials (e.g., soil and rock). Next, consider that unlike virtually all other construction materials (e.g.., concrete, steel, aggregates, etc.), earth materials are not manufactured so there are no manufacturing quality control programs for these unprocessed natural earth materials. Lastly, realize that there is an extremely high level of variability in these earth materials. Consequently, the subsurface exploration and laboratory testing programs are the main tools used to estimate the earth material properties/characteristics that underlie a site. It must be understood that all projects are unique, and the subsurface exploration program for each project must be carefully contemplated and planned to fit