DRILLED SHAFTS:
CONSTRUCTION
PROCEDURES AND
DESIGN METHODS
NOTICE
The contents of this report reflect the views of the authors, who are responsible for the facts and the accuracy of the data presented herein. The contents do not necessarily reflect the policy of the Department of Transportation. This report does not constitute a standard, specifications, 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
4. Title and Subtitle
Drilled Shafts: Construction Procedures and Design Methods
4 Report Date
August 1999
6. Performing Organization Code: 7. Author(s)
Michael W. O'Neil and Lymon C. Reese
I
15. Supplementary Notes
COTR: Mr. Chien-Tan Chang
Technical Assistance: Mr. Richard S . Cheney, P.E. Technical Review and Revision: Mr. Sumant Singla
8. Performing Organization Report No.
9. Performing Organization Name and Address ( 10 Work IJnit No (TRAIS)
All American Soils
1792 1 Sky Park Circle, Suite J Irvine, C A 926 14
12. Sponsoring Agency Name and Address
Federal Highway Administration
Office o f Infrastructure/Office o f Bridge Technology I-IIBT, Room 3203
400 7" Street S.W. Washington D.C. 20590
16. Abstract:
This manual is FHWA's primary reference of recommended construction procedures and design methods for drilled shafts. 1 I . Contract or Grant No.
DTFH6 1-96-2-0005 1
13 Type of Report and Period Covered
Technical Manual
14. Sponsoring Agency Code
This document was written as a resource for participants in a short course covering the topic of construction and design of drilled shaft foundations for bridges and other structures. It is the second edition of an FHWA workbook on construction and design of drilled shafts. The first edition was written in 1988 ( FHWA Publication No. FHWA-SA-HI-88-042). While introductory material from the 1988 edition was retained, the emphasis in this document is on providing relatively
comprehensive information for engineers who already have some experience with drilled shaft construction and/or design. The initial chapters cover an overview of the characteristics of drilled shafts, site investigations for drilled shafts (to collect information for both construction and design), and details of drilled shaft construction. These chapters are followed by several chapters on the design of drilled shafts in soil and rock for both axial and lateral loading, with examples. Both allowable stress design and load and resistance factor design principles are addressed. Details of design calculations
procedures are provided in the appendices. Procedures for performing load tests, an important component of design, are then reviewed, following which model construction specifications are presented and discussed. The latter chapters of the
document deal with construction inspection, structural integrity testing, repair of defective drilled shafts and cost estimation. The chapter on inspection includes acceptance criteria and is intended to complement other short courses and documents on drilled shaft construction inspection.
Page Technical Report Documentation
1. Report No.
FHWA-IF-99-025
17. Key Words
Foundations, Drilled Shafts, Construction, Design, Soil, Rock, Computations, Specifications
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2. Government Accession No.18. Distribution Statement
N o restrictions. This document is available to the public from the National Technical Information Service, Springfield, Virginia 22 16 1
I
3. Recipient's Catalog No
19. Security Classif. (of this report)
Unclassified
?arm DOT F 1700.7 (8-72) Reproduction o f completed page authorized
20. Security Classification (of this page)
Unclassified
2 1 . No. of Pages
758
PREFACE
The Federal Highway Administration has produced two educational publications (in 1977 and 1988) on the construction and design of drilled shaft foundations. The second publication, Publication No. FHWA-HI-88-042, July 1988, has been used as the textbook to teach over 50
three-day short courses on drilled shafts in over 30 states between 1989 and 1998. However, drilled shaft technology has advanced rapidly since 1988, and it became necessary to revise and update this publication. This present publication is a new, expanded, edition of the 1988 publication, which it is intended to replace. New material contained in the present publication includes operations with polymer drilling slurries, admixtures for drilled shaft concrete, new drilling equipment, specifications for performing non-destructive evaluations, design in intermediate geomaterials and in rock, additional material on structural design, LRFD procedures, and methods for analyzing groups of drilled shafts.
The main text addresses most common design and construction conditions. The appendices contain supporting material that may need to be used in certain circumstances and that gives foundation engineers detailed information not available in the text. Tt is intended that this publication serve as a living reference document that will be updated continually as further advances in the construction and design of drilled shafts take place.
The authors express gratitude to Axiom Engineering and Science company, which compiled the text for this publication. They are also grateful to ADSC: The International Association of Foundation Drilling, its Executive Director, Mr. Scot Litke, and its technical review committee, chaired by Mr. Ed Nolan; Dr. Alaa Ata and Mr. Jose Arrellaga, who each reviewed all or parts of the document and provided considerable valuable input. The senior author also thanks his
colleagues at the University of Houston, Dr. Cumaraswamy Vipulanadan and Dr. Sarni Tabsh for their helpful comments about behavior of cementious materials and structural design of drilled shafts, respectively, and to many colleagues, too numerous to name here, who provided
photographs. Michael W. O'Neill Lymon C . Reese
ENGLISH TO METRIC (SI) CONVERSION FACTORS
The primary metric (SI) units used in civil and structural engineering are:
length meter (m)
mass kilogram (kg)
time second (s)
force newton (N) or kilonewton (kN)
pressure pascal (Pa = N/m2) or kilopascal (kPa = kN/m2)
The following are the conversion factors for units presented in this manual: Quantity Mass Force Force/unit length Pressure, stress, modulus of elasticity Length Area Volume
A few points to remember:
1. In a b'soft" conversion, an English measurement is mathematically converted to its exact
metric equivalent.
2. In a "hard" conversion, a new rounded, metric number is created that is convenient to work with and remember.
3. Use only the meter and millimeter for length (avoid centimeter). 4. The pascal (Pa) is the unit for pressure and stress (Pa = ~ / m ~ ) . 5. Structural calculations should be shown in MPa or kPa.
6. A few basic comparisons worth remembering to help visualize metric dimensions are: One mm is about 1/25 inch or slightly less than the thickness of a dime.
One m is the length of a yardstick plus about 3 inches.
One inch is just a fraction (1164 inch) longer than 25 mm (1 inch = 25.4 mm). Four inches are about 1/16 inch longer than 100 mm (4 inches = 101.6 mm). One foot is about 3/16 inch longer than 300 mm (12 inches = 304.8 mm).
TABLE OF CONTENTS
CHAPTER 1 : INTRODUCTION
...
1TYPES OF DEEP FOUNDATIONS ... 1
DESCRIPTION OF DRILLED SHAFTS ... 1
BRIEF HISTORY OF DRILLED SHAFT FOUNDATIONS
...
4MOTIVATION FOR USING DRILLED SHAFTS ... 6
REVIEW OF CURRENT PRACTICE
...
10Construction ... 10
Design for Axial Load
...
12Design for Lateral Load
...
14APPLICATIONS OF DRILLED SHAFTS
...
14ADVANTAGES AND DISADVANTAGES OF DRILLED SHAFTS
...
15Advantages
...
15Disadvantages
...
19TRAINING RESOURCE
...
20REFERENCES
...
-20CHAPTER 2: SITE CHARACTERIZATION ... 22
PURPOSE OF SITE CHARACTERIZATION
...
22SITE INVESTIGATIONS
...
23General
...
23Surface Features
...
24Subsurface Pipelines, Cables, and Other Obstructions
...
25Preliminary Subsurface Mapping
...
25Detailed Site Investigations
...
27...
TECHNIQUES FOR SUBSURFACE INVESTIGATIONS 28 Information Required for Design...
28...
Information Required for Construction 33...
Comments 34...
Full-Sized Test Excavations 35 UNCERTAINTY IN SOIL OR ROCK PROPERTIES AT A SITE...
36EFFECTS OF PILES AND DRILLED SHAFTS ON SOIL AND ROCK
...
PROPERTIES 37...
Installation in Clays 37 Installation in Sands...
38 Installation in Rock...
..39SOIL AND ROCK MECHANICS RELATED TO DRILLED SHAFT DESIGN
...
40REFERENCES
...
46...
CHAPTER 3: GENERAL CONSTRUCTION METHODS 49...
INTRODUCTION 49 UNDERREAMS (BELLS)...
50...
VERTICAL ALIGNMENT 53...
DRY METHOD OF CONSTRUCTION 53...
CASING METHOD OF CONSTRUCTION 56 WET METHOD OF CONSTRUCTION...
63...
The Static Process 64
...
The Circulation Process 68
RELATIONSHIP OF CONSTRUCTION METHOD TO DESIGN
...
PHILOSOPHY 69
...
REFERENCES 71
...
CHAPTER 4: METHODS OF EXCAVATION 72
...
EXCAVATION BY ROTARY METHODS 72
...
...
Truck-Mounted Drilling Machines
.
.
.
73Crane-Mounted Drilling Machines
...
73...
Special Mounts For Drilling Machines 76
...
Low Headroom Drilling Machines 77
...
Summary of Rotary Drilling Machine Characteristics 77
Tools for Rotary Drilling
...
79Drilling Bucket
...
79...
Flight Augers (Open Helix) 80
...
Rock Auger 83 Core Barrel...
85 Shot Barrel...
85...
Full-Faced Excavators 87Undeneamers or Belling Buckets
...
87...
Special Tools 87
EXCAVATION BY PERCUSSION METHODS
...
87...
Lifting Machines 88
Clamshell or Grab Bucket
...
.
.
...
88...
Rock Breakers -88
...
Hammergrabs 92
OTHER METHODS OF EXCAVATION
...
92...
Rodless Drill 92
Air-Operated Hammers
...
.
.
...
94...
Use of Drilling Fluid 95
...
...
Grouting.
.
95...
Mining Techniques -95...
REFERENCES 96CHAPTER 5: CASINGS AND LINERS
...
.
.
...
97TEMPORARY CASING
...
97...
PERMANENT CASING 98
INFLUENCE OF CASING ON LOAD TRANSFER
...
99...
TYPES AND DIMENSIONS 101
...
PROBLEMS OF PLACEMENT AND RECOVERY 103
...
...
DESIGN CONSIDERATIONS.
.
.
.
105...
...
REFERENCES.
.
.
-105...
FABRICATION AND STORAGE 177
...
CONSIDERATIONS RELATED TO METHOD OF CONSTRUCTION 177
REFERENCES
...
.
.
.
...
179...
CHAPTER 8: DESIGN AND PLACEMENT OF CONCRETE 180...
BASIC CHARACTERISTICS OF DRILLED SHAFT CONCRETE 180 MIX DESIGN...
182 Cementitious Materials...
182 Cement...
182 Pozzolanic Additives...
182 Expansive Additives...
183 Chemical Admixtures...
.
.
...
184 Air-entraining agents...
184 Retarders...
,185 Water Reducers...
185 Accelerators...
-186 Other Admixtures...
186Aggregate and Water
...
186Workability
...
187Mix Proportions
...
187Strength
...
194CONCRETE TESTS
...
194Tests at the Batch Plant
...
194Tests at the Jobsite
...
-195Addition of Water at Job Site
...
196PLACEMENT OF CONCRETE
...
197Placement by Free Fall
...
197Placement of Concrete by Tremie
...
200Placement by Gravity-Fed Tremie
...
,201Placement by Pump
... ..
..
..
..
..
..
..
..
..
...
208DRILLING NEAR A RECENTLY CONCRETED SHAFT
...
.
.
....
215CONCRETING CURVES
...
216CONTAMINATED CONCRETE AT SHAFT HEAD
...
219POST-GROUTING
...
220REFERENCES
...
-220CHAPTER 9: CASE STUDIES OF DRILLED SHAFT CONSTRUCTION UNDER VARIOUS CONDITIONS
...
224INTRODUCTION
...
...
...
224...
CHAPTER 10: DESIGN CONCEPTS FOR DRILLED SHAFTS 225 INTRODUCTION...
225...
The Design Process 225 Importance of subsurface Investigation...
226...
Influence of Construction on Geomaterial Properties ...231...
Cohesive Soil...
...
232Granular soil and Granular IGM's
...
233...
Rock and Cohesive IGM's 234
...
Principal Design Considerations 235
GENERAL APPROACHED TO DESIGN
...
238 ...Allowable Stress Design 239
Load and Resistance Factor Design
...
240 ... ...Comparison of ASD and LRFD
.
.
241COMPUTATION OF A NOMINAL ULTIMATE AXIAL RESISTANCE, RTN
...
2 4 3...
Nominal Base Resistance, RBN 247
...
...
Cohesive Soil
.
.
247...
Granular Soil and Cohesionless Intermediate Geomaterials 248
...
Rock and Cohesive Intermediate Geomaterials 250
Nominal Side Resistance, RSN
...
250 Cohesive Soil...
.
.
...
250...
Granular Soil and Cohesionless Intermediate Geomaterials 251
...
Rock and Cohesive Intermediate geomaterials 252
COMPUTAION OF DEFORMATIONS
...
.
.
...
253 GROUPS OF DRILLED SHAFTS...
254...
TOLERABLE MOVEMENTS 257 ... STRUCTURAL DESIGN 258...
REFERENCES 259...
CHAPTER 11: GEOTECHNICAL DESIGN FOR AXIAL LOADING -262
...
INTRODUCTION 262
DIRECTION OF SIDE AND BASE RESISTANCE
...
262 DESIGN OF DRILLED SHAFTS UNDER AXIAL LOADING...
264 STEP-BY-STEP DESIGN PROCEDURES FOR AXIAL LOAD DESIGN ... 266...
REFERENCES 296
CHAPTER 12: DESIGN FOR VERTICAL MOVEMNET OF THE GROUND
...
SURFACE 297...
INTRODUCTION -297...
DOWNDRAG -297...
Occurrence 297Estimating the Neutral Point Location and Distribution of Load and
...
Resistance 301...
Design Solutions 303...
UPLIFT 307Occurrence and Identification of Expansive Soils
...
307 Estimating the Depth of the Zone of Seasonal Moisture Change...
309...
Design Solutions 310...
RESOURCE 316...
REFERENCES 1 6...
CHAPTER 13: DESIGN FOR LATERAL LOADING AND STRUCTURAL DESIGN 319
...
INTRODUCTION 319
...
EXAMPLES OF LATERAL LOADING 319
...
...
Single-Column Support for a Bridge
...
3 19Foundation for an Overhead-Sign Structure
...
321...
Drilled-Shaft-Supported Bridge Over Water 321 Foundation for a Bridge Abutment...
322Foundation for an Arch Bridge
...
322Stabilization of a Moving Slope and Earth Retaining Structures
...
324COMPUTING PENETRATION, DEFORMATIONS, MOMENTS AND
...
SHEARS 327 Characteristic Load Method...
327...
p-y Method 337 Simulation of Nonlinear Bending in Drilled Shafts Using the p-y Method...
342Simulation of Group Action Using the p-y Method
...
347Other Methods of Analysis of Laterally Loaded Drilled Shafts and Drilled Shaft Groups
...
350...
STRUCTURAL DESIGN 351 Cases with Axial Load Only...
352...
Cases with Axial Load and Bending Moment 353...
General Concepts 353 Structural Design Procedure: Longitudinal Reinforcement...
354Structural Design Procedure: Minimum Longitudinal Reinforcement
...
362Design of Transverse Reinforcement
...
363Spiral Column Design
...
363Tied Coiumn Design
...
366Design for Transverse Shear Forces
...
367Depth of Code-Controlled Transverse Reinforcement
...
....
370Splices, Connections and Cutoffs
...
370Analysis to Obtain Distribution of Moment and Shear with Depth: Step-by-step Procedure for Design (p-y method)
...
371STRUCTURAL ANALYSIS OF PLAIN-CONCRETE UNDERREAMS
...
378RESOURCES
...
381REFERENCES
...
381CHAPTER 14: FIELD LOADING TESTS
...
386PURPOSE OF LOADING TESTS
...
386...
AXIAL LOADING TESTS ..387Considerations in Sizing, Locating and Constructing the Test Shaft
...
387Methods of Applying Compressive Loads
...
391Conventional Loading Test Arrangements
...
391Osterberg Cell Testing Arrangement
...
393R Statnamic Testing Arrangement
...
399Conventional Uplift Testing
...
402Instrumentation
...
403Proof Test
...
403...
Testing Procedures . 4 12
...
Data and Analysis ,413
...
LATERAL LOADING TESTS
...
.
.
.
...
.
.
.
...
.
.
415...
Conventional Test 416...
Osterberg Cell Test ,418 R...
Statnamic Test 419 TYPES OF PROJECTS TO WHICH LOADING TESTS ARE APPLICABLE...
419...
INFORMATION ON COST 419...
REFERENCES...
...
420CHAPTER 15: GUIDE DRILLED SHAFT CONSTRUCTION SPECIFICATIONS
...
423...
INTRODUCTION...
.
.
423...
...
Construction Method.
.
.
.
424...
...
Drilling Slurry.
.
.
424...
...
Payment for Shaft Excavation.
.
425...
...
Qualification of Drilled Shaft Contractors for Bidding.
..
..
..
426...
... ...
Special Bidding Requirement.
.
.
.
.
426...
...
GUIDE DRILLED SHAFT CONSTRUCTION SPECIFICATIONS.
.
426.
...
ITEM xxx DRILLED SHAFTS 428...
...
xxx.
10 DESCRIPTION.
.
.
.
.
.
.
428xxx.11 QUALIFICATIONS OF DRILLED SHAFT CONTRACTOR:
...
428...
...
xxx.
12 SUBMITTALS:.
.
428xxx
.
13 TRIAL SHAFT INSTALLATION:...
430xxx.20 MATERIALS:
...
431xxx.30 CONSTRUCTION METHODS AND EQUIPMENT:
...
-433xxx.3 0.1 PROTECTION OF EXISTING STRUCTURES:
...
433...
xxx.30.2 CONSTRUCTION SEQUENCE: 434 xxx.30.3 GENERAL METHODS AND EQUIPMENT:...
.
.
.
.
...
434xxx.3 1 DRY CONSTRUCTION METHOD:
...
.
.
.
...
435xxx.32 WET CONSTRUCTION METHOD:
... .
..
..
..
...
436xxx.33 CASING CONSTRUCTION METHOD:
...
.
.
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436xxx.34 EXCAVATION AND DRILLING EQUIPMENT:
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437xxx.35 EXCAVATIONS:
...
.
.
.
.
.
...
437 xxx.35.1 UNCLASSIFIED EXCAVATION:...
438...
xxx.35.2 CLASSIFIED EXCAVATION: 438...
xxx.35.2 1 STANDARD EXCAVATION: 438...
xxx.35.22 SPECIAL EXCAVATION: 439...
xxx.35.3 OBSTRUCTIONS: 439...
...*...*..
xxx.35.4 LOST TOOLS:.
.
.
439xxx.3 5.5 EXPLORATION (SHAFT EXCAVATION):
... .
.
.
.
.
...
439xxx.36 CASINGS:
...
441...
xxx.36.1 TEMPORARY CASING:...
.
.
.
.
441...
...
xxx.36.2 PERMANENT CASING:.
.
.
443...
xxx.3 8 SLURRY. 443 xxx.40 EXCAVATION JNSPECTION:...
447 xxx.4 1 CONSTRUCTION TOLERANCES:...
.
.
.
...
448xxx.50 REINFORCING STEEL CAGE CONSTRUCTION AND PLACEMENT:
...
451...
...
xxx.60 CONCRETE PLACEMENT:.
.
452...
xxx.61 TREMIES: 453...
xxx.62 PUMPED CONCRETE: 453...
...
xxx.63 DROP CHUTES:.
.
.
454...
...
xxx.64 NONDESTRUCTIVE EVALUATION:.
.
455...
xxx.64.1 TESTS IN ACCESS TUBES: 455...
xxx.64.2 SONIC ECHO TESTS: 456...
xxx.70 DRILLED SHAFT LOAD TESTS: 458 xxx.7 1 METHOD OF MEASUREMENT:...
460...
xxx.7 1.1 FURNISHING DRILLED SHAFT DRILLING EQUIPMENT: 460 xxx.7 1.2 DRILLED SHAFTS:...
-460...
...
xxx.7 1.3 STANDARD EXCAVATION:.
.
.
460...
xxx.7 1.4 SPECIAL EXCAVATION:.
.
.
...
460xxx.7 1.5 UNCLASSIFIED SHAFT EXCAVATION:
...
460...
xxx.7 1.6 UNCLASSIFIED EXTRA DEPTH EXCAVATION. 461 xxx.7 1.7 OBSTRUCTIONS:...
461xxx.7 1.8 TRIAL SHAFT:
...
461..
xxx.7 1.9 EXPLORATION (SHAFT EXCAVATION):...
.
.
461...
xxx.71.10 LOAD TESTS: 461.
...
xxx.7 1 1 1 PERMANENT CASING:...
.
.
461...
xxx.7 1.12 INSTRUMENTATION AND DATA COLLECTION: 462...
xxx.71.13 PROTECTION OF EXISTING STRUCTURES: 462...
xxx.71.14 ACCESS TUBES: 462...
xxx.71.15 NON-DESTRUCTIVE EVALUATION TESTS: 462...
xxx.72 BASIS OF PAYMENT: 462 xxx.72.1 FURNISHING DRILLED SHAFT DRILLING EQUIPMENT:...
462xxx.72.2 DRILLED SHAFTS:
...
-462xxx.72.3 STANDARD EXCAVATION:
...
463...
...*.
xxx.72.4 SPECIAL EXCAVATION:..
..
463...
xxx.72.5 UNCLASSIFIED SHAFT EXCAVATION: 463...
xxx.72.6 UNCLASSIFIED EXTRA DEPTH EXCAVATION. -463 xxx.72.7 OBSTRUCTIONS:...
.
.
...
464xxx.72.8 TRIAL SHAFT HOLES:
...
...465xxx.72.9 EXPLORATION (SHAFT EXCAVATION):
...
465xxx.72.10 LOAD TESTS:
...
465xxx.72.11 PERMANENT CASING:
...
465xxx.72.12 INSTRUMENTATION AND DATA COLLECTION:
...
465xxx.72.13 PROTECTION OF EXISTING STRUCTURES:
...
.
.
.
...
465xxx.72.14 ACCESS TUBES:
...
465xxx.72.15 NON-DESTRUCTIVE EVALUATION TESTS:
...
466xxx.72.16 ITEMS OF PAYMENT:
...
466ADDENDUM
-
SHAFT EXCAVATION IN ROCK BY BLASTING:...
466Construction Requirements
...
466CHAPTER 16: INSPECTION AND RECORDS
...
......
469 ......
RESPONSIBILITIES.
.
469...
CONSTRUCTION CONFERENCES 470...
UNANTICIPATED CONDITIONS 470 ......
SITE CONDITIONS.
.
471 ... CONSTRUCTION OPERATIONS 471...
Excavation 472 Reinforcing Steel...
472 Drilling Slurry...
472...
Concrete Quality and Placement 472 Completed Drilled Shaft...
477COMMON PROBLEMS
...
477 INSPECTION FORMS...
477 ACCEPTANCE CRITERIA...
478...
RESOURCES 480...
REFERENCES 480...
CHAPTER 17: TESTS FOR COMPLETED DRILLED SHAFTS 481...
INTRODUCTION 481 SUMMARY DESCRIPTIONS OF TNTEGRITY TESTS...
483Sonic Echo Test
...
483...
Impulse-Response Test 487 Impedance Log...
489...
Parallel Seismic Test.
.
...
490...
Internal Stress Wave Test 491 Drilling and Coring...
494Crosshole Acoustic (Sonic and Ultrasonic) Tests
...
495...
Gamma-Gamma Testing 499...
...
Concreteoscopy.
.
501...
Other Procedures SO4...
EXPECTED DEFECT RATE FOR DRILLED SHAFTS 504 DESIGN OF AN INTEGRITY TESTING PROGRAM AND ACCEPTANCE...
CRITERIA BASED ON INTEGRITY TESTJ3G 505...
EVALUATING DEFECTS 511...
REFERENCES 512...
CHAPTER 18: REPAIR OF DEFECTIVE DRILLED SHAFTS 515...
TYPES OF DEFECTS 515...
Defects at the Base of the Drilled Shaft 515...
Poor Concrete Along the Length of the Shaft 516...
Inadequate Contact Along Sides of Shaft 516...
Incorrect Dimensions and/or Location ,517...
...
METHODS OF REPAIR..
..
..
517...
Grouting 517...
Hand Repairs 519...
...
Underpinning with Microshafts
.
.
S 19...
Removal and Replacement 522
Straddle Shafts
...
-522REFERENCES
...
-524CHAPTER 19: COST ESTIMATION
...
525GENERAL
...
525FACTORS INFLUENCING COST
...
..525COMMENTARY ABOUT COST
...
527COST SURVEY
...
...
...
527...
ON-LINE DATA BASES 533 CONTRACTORS' COST COMPUTATION...
536EXAMPLES
...
536Texas
...
536Florida
...
537LIST OF APPENDICES
...
APPENDIX A: ELEMENTS OF LRFD FOR DRILLED SHAFTS A-1
QUANTIFICATION OF UNCERTAINTY OF SOIL PROPERTIES
...
...
A-1 Suggested Approximate Statistical Test for Site Variability...
A-3...
...
...
Further Reading
....
.
.
A- 10BASIC CONCEPT OF RELIABILITY
...
A-11...
...AASHTO LIMIT STATES
.
.
A- 17...
RESISTANCE FACTORS FOR DRILLED SHAFTS A-21
MODIFYING RESISTANCE FACTORS FOR DRILLED SHAFTS
...
A-23 FORMAL STEP-BY-STEP PROCEDURE FOR APPLYING LRFD TO THE...
DESIGN OF DRILLED SHAFTS A-24
...
EXAMPLE PROBLEM A-26
...
REFERENCES A-29
APPENDIX B: COMMENTARY ON METHODS OF COMPUTING THE NOMINAL
...
AXIAL RESISTANCE OF DRILLED SHAFTS B-1
...
INTRODUCTION B- 1
...
BASIC DESIGN EQUATIONS FOR GEOTECHNICAL AXIAL RESISTANCE B- 1
...
Compression Loading B- 1...
Uplift Loading B-3...
Downdrag B-3...
IDEALIZATION OF GEOMATERIALS B-4...
BASE RESISTANCE, RB B-7Bearing Capacity Equation
...
B-7 Drained and Undrained Loading...
B-8...
Undrained Loading
.
.
...
B-9 Evaluating the Shear Strength...
B-9...
Drained Loading B- 19
...
Drained Loading in Soil B- 19
Drained Loading in Preferentially Sloping, Jointed Rock
...
B-22 SIDE RESISTANCE, Rs...
B-26 Undrained Loading...
B-26 Cohesive Soils...
B-26 Cohesive Intermediate Geomaterials-
Compression Loading...
B-28 Cohesive Intermediate Geomaterials-
Uplift Loading...
...
B-37...
Rock
-
Compression Loading B-38...
Rock
-
Uplift Loading B-42Rock
-
Adding Base and Shaft Resistance...
.
.
.
...
B-42...
...
Drained Loading
....
B-43Cohesive Soils
-
Compression Loading...
B-43 Cohesive Soils-
Uplift Loading...
B-45 Granular Soils-
Compression Loading...
B-45 Granular Soils-
Uplift...
B-49 Cohesionless Intermediate Geomaterials-
Compression...
B-51 Cohesionless Intermediate Geomaterials-
Uplift Loading...
B-52...
Intermediate Geomaterials .. Considerations for Desert Regions B.52 Rock...
B-53 Cyclic Axial Loading...
B-53 Combined Axial and Lateral Loading...
B-55 AXIAL GROUP EFFECTS...
B-56 RELIABILITY OF DESIGN EQUATIONS FOR AXIAL RESISTANCE...
B-61 ALTERNATIVE METHODS FOR ESTIMATING AXIAL RESISTANCE OFDRILLED SHAFTS
...
B-62 OTHER SOURCES OF INFORMATION...
B-64 RESOURCES...
B-64 REFERENCES...
B-65 APPENDIX C: ESTIMATION OF AXIAL MOVEMENT OF DRILLED SHAFTS...
C-1 INTRODUCTION...
C-1 SOILS-
SIMPLE FORMULAS...
C-2 Single Drilled Shafts in Soil...
C-2 Groups of Drilled Shafts in Soil...
.
.
...
C-4 SOILS-
NORMALIZED LOAD-TRANSFER METHODS (COMPRESSION)...
C-5 SOILS AND IGM'S-
COMPUTER SIMULATION METHODS...
C-12 IGM's-
SIMPLIFIED EQUATIONS BASED ON ANALYTICAL SOLUTIONS...
C-19 Cohesive IGM's...
C- 19 Granular (Cohesionless) IGM's...
C-21 ROCK...
C-27 GROUPS OF DRILLED SHAFTS IN SOIL AND ROCK...
C-32 Equivalent Raft Method...
C-32 Equivalent Pier Method...
.
.
.
.
...
C-36 CYCLIC LOADING IN THE SERVICE LOAD RANGE...
.
.
...
C-45 RESOURCES...
C-46 REFERENCES... ...
C-46 APPENDIX D: EXAMPLE DESIGN PROBLEMS...
D-1EXAMPLE D- 1 : LRFD of a Drilled Shaft in Layered Cohesive Soil and Cohesive
Intermediate Geomaterial
...
D- 1...
...
Work Table for Example D.1. Step 15
.
.
D-5...
EXAMPLE D-2: Drilled Shaft to Rock by LRFD D-8
EXAMPLE D-3: Design of a Drilled Shaft in Mixed Cohesionless Geomaterial by
ASD
...
D- 15 Work Table for Example D.3. Step 14...
D- 18 EXAMPLE D-4: Design of a Drilled Shaft in Cohesive Intermediate Geomaterialby LRFD
...
D-21...
APPENDIX E: EXAMPLE SOLUTIONS FOR A DOWNDRAG PROBLEM E-1
...
Example Ela: Hand Solution with total stress parameters
...
.
.
E-1 Example E l b: Hand Solution Using Effective Stress Parameters...
E-4 Example E2: Computer solution using elastic-plastic side load transfer relations...
E-7...
APPENDIX F: INSPECTION. REPORTING AND BIDDING FORMS F-1
APPENDIX G: CONSTRUCTION CASE HISTORIES
...
G- 1 CASE 1: STIFF CLAY. WATER TABLE SLIGHTLY BELOW BASE OFSHAFT
...
G- 1 CASE 2: HARD CLAY AND SHALE WITH LAYER OF WATER-BEARINGSAND
...
G-3 CASE 3: SOFT CLAY ABOVE JOINTED AND SLICKENSIDED CLAY...
G-5 CASE 4: DRY SAND...
G-6 CASE 5: GRANULAR SOIL BELOW THE WATER TABLE...
G-8 CASE 6: CAVING SOIL ABOVE SOUND ROCK...
G-10 CASE 7: CAVING SOIL ABOVE FRACTURED ROCK...
G-12 CASE 8: BOULDER FIELDS...
G-14...
CASE 9: IRREGULARLY WEATHERED ROCK G- 16
CASE 10: KARSTIC AND OLD MINING REGIONS
...
...
.
.
G-20 CASE 11 : CONSTRUCTION IN OPEN WATER...
G-22CASE 12: CONSTRUCTION IN AN ENVIRONMENTALLY SENSITIVE
AREA
...
G-23 REFERENCES...
G-26LIST OF FIGURES
Title Page No
.
Schematic of a typical drilled shaft
...
2A typical construction job in progress (Photograph courtesy of Watson. Inc.)
...
3Photograph of Queets River Bridge at time of completion (Note old bridge in
background and flood debris against the columns)
...
8 Construction of drilled shafts from barge in the Great Pee Dee River...
10 Cases for use of drilled shafts: (a) bearing in hard clay. (b) skin friction design. (c)socket into rock. (d) installation into expansive clay (continued)
...
16 (continued).
Cases for use of drilled shafts: (e) stabilizing a slope, ( f ) foundationfor overhead sign, (g) foundation near existing structure, (h) closely-spaced drilled shafts to serve as a cantilever or tied-back wall (drilled shafts installed
prior to excavation)
...
17 (continued).
Cases for use of drilled shafts: (i) foundation at a marine site, and (i)pier protection or navigation aid
...
18 Subsurface characterization related to design and construction...
22 Low-frequency continuous seismic reflection profile for the Connecticut River atthe Glastonbury-Wethersfield Bridge (Haeni, 1988)
...
26 Kriging surfaces for three layers at overconsolidated clay site (Yoon and O'Neill,1996)
...
27 Schematic elevation showing definition of vertical and horizontal effectivestresses in the ground .
...
.
.
...
32...
...
Wet rotary-type soil boring rig
.
.
35Illustration of the concept of dilation at the interface of concrete and rock (O'Neill
et al.. 1996)
...
..
....
...
41 Effect of borehole smear on load-settlement behavior of a drilled shaft in rock(Hassan and O'Neill, 1997)
...
41...
...
Possible sliding surface when a drilled shaft is pushed downward
.
.
42...
Friction angles for sand at or near the wall of a drilled shaft 44
...
Failure relationship for saturated clay at or near the wall of a drilled shaft 44 Shapes of typical kderreams (a) cut with "standard" conical reamer; (b) cut with
...
"bucket. " or hemispherical. reamer 51
Dry method of construction: (a) initiating drilling (b) starting concrete pour. (c)
...
placing rebar cage. (d) completed shaft 5 5
Casing method of construction: (a) initiating drilling, (b) drilling with slurry; (c) introducing casing, (d) casing is sealed and slurry is being removed from
interior of casing (continued)
...
61 (continued).
Casing method of construction: (e) drilling below casing,...
( f ) underreaming, (g) removing casing, and (h) completed shaft
...
.
.
62 Alternate method of construction with casing: (a) installation of casing, (b)....
...
drilling ahead of casing, (c) removing casing with vibratory driver
.
.
63...
Case-and-drill (full-depth-casing) rigs: (a) track-mounted rig with auger 65
...
(continued) (b) skid-mounted rig with hammergrab 65
Slurry method of construction (a) drilling to full depth with slurry; (b) placing
rebar cage; (c) placing concrete; (d) completed shaft
...
.
.
...
67 Effect of time lapse between drilling and concreting on CPT resistance of sandadjacent to drilled shafts constructed by the wet method: (a) Two hours between completion of drilling and concreting. (b) Two weeks between completion of
drilling and concreting (De Beer. 1988)
...
70...
A typical truck-mounted drilling machine 74
A typical crane-mounted drilling machine (Photograph courtesy of Farmer
...
Foundation Company, Inc.) .75
...
A typical crawler-mounted drilling machine (Courtesy of Case Pacific Company) 76 Low-headroom drilling machine (crawler-mounted)(Photograph courtesy of A
.
H.
...
...
Beck Foundation Company)
.
.
77...
...
A typical drilling bucket
.
.
80...
...
A typical "muck bucket" or "clean-out bucket"
.
.
.
.
.
.
.
81...
A single-flight auger 82
...
...
A typical double-flight auger
.
.
82A typical rock auger
...
.
.
...
84 Tapered rock auger for loosening fragmented rock (Photograph courtesy of John...
...
Turner)
.
.
-84...
...
A typical single-walled core barrel
...
.
.
.
...
86. . .
...
A double-wall core barrel (Photograph courtesy of W F J Drilling Tools, Inc.) 86 Full-faced tool with roller bit (Photograph courtesy of Caissons, Inc.)
...
.
.
.
...
A9 A typical closed belling tool inserted into a borehole...
.
.
.
...
89...
A typical belling bucket in drilling position 90
.
...
A Glover rock-grab (Drawing courtesy of Steven M Hain)
.
.
.
.
...
90...
...
A typical grab bucket (Photograph courtesy of John Turner)
.
.
.
.
.
.
.
.
9 1An example of a churn drill (Photograph courtesy of John Turner)
...
91...
An example of a hammergrab (from LCPC, 1986) -93
An example of a rodless soil drill (Photograph courtesy of Tone Boring Corp.,
...
LtdJ 93
Mach drill (Photograph courtesy of Tone Boring Corp., Ltd.)
...
.
.
.
.
.
.
.
...
94A typical view of stored temporary casing
...
...
...
98...
Examples of use of permanent casing -99
J slots in top of casing for use with casing twister (Photograph courtesy of Herzog
...
...
Foundation Drilling, Inc.)
.
.
.
.
.
. .
104Teeth for use in sealing casing into rock (Photograph courtesy of Herzog
...
...
Foundation Drilling, Inc.)
.
.
.
.
.
104Formation of mudcake and positive effective pressure in a mineral slurry in sand
formation
...
.
.
...
110 Mineral slurry plates in pores of open-pored formation (modified after Fleming...
and Sliwinski, 1977) 111
Stabilization of borehole by the use of polymer drilling slurries
...
113...
Relation of viscosity of mineral slurries to dosage (after Leyendecker, 1978) 120 Schematic diagram of unit for mixing and treating mineral slurry
...
126...
...*...
Sampler for sluny (from Fleming and Sliwinski, 1977)
.
.
.
.
.
130...
Schematic of viscometer 132
...
.
Interpretation of data from a viscometer (Ata and O'Neill. 1997)
.
.
.
.
134...
Photograph of sand content test (backwashing sand into burette) 135 Photograph of titration test for hardness...
136...
Photograph of complete set of field testing equipment for drilling slurries 138...
Commercial borehole caliper (Western Atlas. Inc.) 141. .
...
(a) Sensors in retracted pos~tion 14 1...
(b) Sensors extended ,141...
Caliper log (Foundations for US 23 1 Crossing of Ohio River) 142 The buildup of bentonite filter cake in a model apparatus in response to different...
...
pressure heads (after Wates and Knight. 1975).
.
.
.
149...
Placing concrete through heavily-contaminated slurry 153...
...
Factors causing weakened resistance at base of a drilled shaft.
.
154...
Placing casing into mineral slurry with excessive solids content 156...
Pulling casing with insufficient head of concrete 157 Placing concrete where casing was improperly sealed...
158...
View of a rebar cage being assembled, showing longitudinal steel 166 View of bundles of No.
18 rebar in a drilled shaft cage...
166Transverse ties and spiral steel, showing hook anchors and spiral laps
...
168Possible distortion of poorly assembled cage due to pickup forces or hydraulic
...
...
forces from fresh concrete.
.
.
.
.
.
..
....
168...
Sizing hoop assembly (from LCPC, 1986) 170...
Centering with plain, epoxy-coated rebar skids (from LCPC, 1986) 171...
Concrete rollers 172...
Installation of rollers: (a) correct, (b) incorrect (from LCPC, 1986) 173 Transverse stiffeners for temporary strengthening of the rebar cage (after LCPC,...
1986) 174 Longitudinal stiffeners for temporary or permanent strengthening of a rebar cage (from LCPC, 1986)...
175Photograph of bands used for strengthening lower part of a rebar cage
...
175Photograph of rebar cage being lifted improperly (Photo courtesy of Barry
...
Berkovitz, FHWA) 176 Photograph of rebar cage being lifted properly...
176Inward-turned hooks in a rebar cage for a drilled shaft at an abutment (photograph
...
courtesy of Bany Berkovitz, FHWA) 179 Slump loss relationship from a trial mix design...
189Concrete with insufficient workability for use in drilled shafts
...
193Concrete with high workability but with improper mix design for tremie
...
placement 193 Concrete with high workability and with good mix design for tremie placement...
Strength 194 Placing concrete directly from the ready-mix truck without a dropchute...
198Steel dropchute with multiple windows
...
199Hinged closure (from LCPC, 1986)
...
202"Hat" closure (from LCPC, 1986)
...
202Loose-plate closure
...
202Photograph of simple plywood loose plate closure on a gravity-fed tremie
...
203...
...
12.3. Potential geotechnical strength limit states for drilled shafts
.
.
.
.
...300...
12.4. The equivalent pier concept applied to downdrag in groups of drilled shafts 302 12.5. Elementary mechanics of downdrag: (a) example problem; (b) load transfer
curves; (c) relative movement of drilled shaft with respect to geornaterial (neutral point assumed at bottom of settling stratum); (d) distribution of load along drilled shaft; (e) revised estimate of relative movement of drilled shaft with respect to
...
geomaterial; ( f ) revised estimate of distribution of load along drilled shaft 305
...
...*...*.
12.6. Definition of c' and f where curved failure envelope exists
.
.
.
.
.
306...
12.7. Example soil profile with expansive geomaterial 312
...
...
.
12.8 Use of a permanent surface casing for design in expansive soil
.
.
.
, 3 1 5 12.9. Raba method of design in expansive soil...
315...
...
12.10. Use of rebar cage for design in expansive geomaterial
.
.
3 1 713.1
.
Single-column supports...
320...
13 .2
.
Loadings on single-column support for a bridge 32013.3. Overhead sign
...
..
...
,321 13.4. Elevation view of an overhead sign structure (a) two-shaft foundation and...
(b) single-shaft foundation (from FHWA-IP-84- 1 1) 322
13.5. Bridge abutment
...
-323...
...
13.6. Sketch of foundation for a bridge abutment (FHWA-IP-84-11)
...
323...
...
.
13.7. Arch bridge (photograph courtesy of Ronald C O'Neill)
.
.
.
324...
.
13.8. Reaction block for a c h bridge (photograph courtesy of Ronald C O'Neill) 325
...
13.9. Drilled shaft foundation for an arch bridge (from FHWA-IP-84-1 1) 325
...
...*...
13.10. Drilled shafts for stabilizing a slide (Reese et al., 1987)
.
.
326...
13.1 1
.
Drilled shaft retaining structure for depressed section of highway 326 13.12. Groundline shear - deflection curves for (a) clay and (b) sand (Duncan et al.,1994)
...
.
.
...
330 13.13. Groundline moment-
deflection curves for (a) clay and (b) sand (Duncan et al.,1994)
...
...
330 13.14. Groundline shear - maximum moment curves for (a) clay and (b) sand (Duncan etal., 1994)
...
.
.
...
332 13.15. Parameters A, and B, (Matlock and Reese, 1961)...
332 13.16. Model of a deep foundation under lateral loading showing concept of soil...
response curves 339
...
13.17. Definition of terms in Equations (1 3.12) and (1 3.13). 344
13.18. Variation of EI of a drilled shaft cross section with bending moment and axial
...
load 345
13.19. Assumed stress-strain relation for concrete
...
.
.
.
.
.
...
346...
13.20. Assumed stress-strain curve for steel reinforcement 347
...
...*...*...
13.21. The p-multiplier (Brown and Shie, 1991)
.
.
34913.22. Modification of p-y curve for group action using the p-multiplier
...
.
.
...
349...
13.23. Interaction diagram for a reinforced concrete column 355
13.24. Interaction diagram for factored resistance for combined axial load and flexure
...
364.
13 .25 Deflection, moment and shear as a function of depth for Example 13.5
...
375...
13.26. Results from computer solutions for Example 13.6 (after FH WA-IP-84- 1 1) 377
...
13.27. Typical underream (after Farr, 1974) 379
...
Caliper log for deep drilled shaft in rock 390
Arrangement for testing a drilled shaft conventionally under axial compressive
loading
...
-393...
Osterberg cell loading system 396
(a) Schematic of Osterberg cell test ... 396 (b) Photograph of Osterberg cell
...
.
.
...
396 Side and base load-movement results from an Osterberg cell test on a rock socket...
in granite (Osterberg, 1994) 397
Comparison of mobilized side shear stress along a drilled shaft in Florida limestone for both Osterberg cell (OC) and conventional surface loading at the load corresponding to side shear failure in the OC test from finite element
...
analysis (from O'Neill et al., 1997, after McVay et al., 1994) 398
...
Multiple-level arrangement for Osterberg cells (O'Neill et al., 1997) 399
.
R...
Schematic of Statnamic test 400
Photograph of statnamicR test arrangement, showing masses being accelerated
...
inside gravel-filled sheath 401
...
Arrangement for testing a drilled shaft under uplift loading 403
... Photograph of head of test shaft showing hydraulic jack and electronic load cell 404
...
Photograph of a telltale system 406
...
Photograph of a vibrating wire sister bar 407
The Mustran cell
...
409...
View of a test shaft with contact pressure cells at its base A10
...
Typical set of load distribution curveso btained from use of Mustran cells 411...
Method of analysis of data from axial loading test 414
Arrangement for a conventional full-scale field lateral loading test using a
pushing procedure
...
418 Osterberg Cell arranged for 26.7 MN (3000 ton) lateral loading test in a 1.22m(4ft.) diameter rock socket
...
420...
Concrete curve showing normal amount of overbreak 475
Concrete curve showing an excessive amount of overbreak
...
476 Decision tree for acceptance of drilled shafts (Baker et al., 1993)...
-479 Sonic echo method (after Sliwinski and Fleming, 1983)...
484 A severe defect that can likely be detected by sonic echo testing...
487 Ideal response curve for the impulse-response or vibration test (after Weltman,1977)
...
488 Examples of impedance logs (Davis and Hertlein, 1991)...
489r
.
I he parallel seismic test (Davis, 1995)
...
490 Compression wave propagation method with internal receivers (Hearne et al.,1981)
...
492 Typical results from internal stress wave test (from Harrell and Stokoe, 1984)...
492 Concrete cores from non-defective and defective drilled shafts...
493 (a) Shaft with no defect...
493 (b) Shaft with defect caused when concrete began to set while removing the...
casing 493
Reinforcing cage to which PVC access tubes have been attached
...
496 Diagram of crosshole acoustic logging system (Weltman, 1977)...
498...
17.1 1
.
Crosshole sonic log for a shaft with a known defect (Baker et al.. 1993) 498...
17.12. Gamma-gamma testing system (after Preiss et al.. 1978) 501
...
17.13. Results from gamma-gamma logging of a drilled shaft with four access tubes 502
...
17.14. Photograph of defect similar to the defect that produced the logs in Figure 17.12 503 17.15. Photograph of a small transverse crack in a concrete pile from a concreteoscope
test
...
503...
...
18.1. Visual inspection of the base of a defective drilled shaft
...
520...
18.2. Circular pattern of microshafts to underpin defective drilled shaft 521
...
18.3. Schemes for underpinning a defective drilled shaft with microshafts 522...
18.4. Use of "straddle" shafts
...
.
.
.
.
.
.
523...
...
19.1. Pricing scenario 1 for 1997 ADSC survey
.
.
528...
19.2. Pricing scenario 2 for 1997 ADSC survey 529
...
19.3. Pricing scenario 3 for 1997 ADSC survey 530
...
A
.
1.
Plan view of characterization domain A-7...
A.2. Elevation of borings and values of s, in characterization domain A-8
...
.
A.3. Undrained shear strength (s, ) vs elevation in upper stratum A-8
...
...
.
A.4. Undrained shear strength (s, ) vs elevation in lower stratum
.
.
A-9...
A S
.
Idealized probability distributions of load and resistance on a drilled shaft A-12...
A.6. Definition of the reliability index A- 14
B
.
1.
Illustration of defelection-sofetening behavior of drilled shafts under compressionloading
...
B-2...
B.2. Idealized geomaterial layering for computation of compression resistance B-5...
B.3. Idealized geomaterial layering for computation of uplift resistance B-5
...
B.4. Relation between s, from CIUC tests and UU tests (Chen and Kulhawy, 1994) B-10
...
B.5. Relation between s, from UC tests and UU tests (Chen and Kulhawy, 1994) B-11
...
...
B.6. Fracturing (punching) of a foundation in massive rock or IGM
.
.
.
B-13...
B.7. Bearing capacity factors (Chen and Kulhawy, 1994)
... .
.
.
.
.
.
.
.
B-20 B.8. Bearing capacity factor Ncs as a function of joint slope and relative shear strength...
of joints and intact rock (Carter and Kulhawy, 1988)
...
.
.
B-24 B.9. Correlation between a and s, Ip,
...
B-28 B.10. Factor a for IGM's (O'Neill et al., 1996)...
B-30 B.11. Factor M vs.
concrete slump (O'Neill et al., 1996)...
B-31 B.12. Parameter n for smooth cohesive IGM sockets (O'Neill et al., 1996)...
B-34 B.
13.
Roughness pattern assumed in the development of design equations (O'Neill et al.,1996)
...
B-34 B.
14.
Simplified representation of Poisson=s effect (exaggerated)...
B-38 B.15. Unit shaft resistance versus shear displacement for drilled shaft socket in rock ofmoderate roughness with q, = 3.0 MPa (Baycan, 1996)
...
B-39 B.
16.
Definition of terms in Equation (B.48)...
B-41. .
B 17 Variations of
P
with depth (O'Neill and Hassan, 1994)...
B-48 B.18. q vs.
center-to-center spacing, s, normalized by shaft diameter, Bshaft, forunderrearned drilled shafts in compression in moist silty sand (Modified after
G a g , 1979)
...
B-57 B.19. Relative unit side and base resistances for single shaft and typical shaft in a nine-shaft groups (Liu et al., 1985)
...
B-58Block failure model for drilled shaft group in cohesive soil with cap in contact
with the ground
...
.
.
...
B-60 Computed axial resistance (R, ) vs.
measured axial resistance (R, ) (Isenhower and...
Long, 1997) B-62
Normalized load transfer relations for side resistance in cohesive soil
...
C-6 Normalized load transfer relation for base resistance in cohesive soil...
C-7 Normalized load transfer relations for side resistance in cohesionless soil...
C-7 Normalized load transfer relations for base resistance in cohesionless soil...
C-8 Mechanistic model of axially loaded drilled shaft...
C-14...
Element from an axially loaded shaft C- 14
...
Illustration of the definition of C- 16
Segment of a load-distribution curve along an axially loaded drilled shaft
...
C-18 Idealized soil modulus profile for computing settlement in granular IGM's...
C-22 Load-settlement relation for method for granular IGM's...
C-22 Vertical strain influence factors below center of rectangular area (Poulos, 1993)...
C-35 Embedment correction factor (after Poulos, 1993)...
C-36 Influence factor I, for drilled shaft groups for EJE', = 88 and n,, il = 0.3 (Poulos,...
1994) C-38
...
Weighting factors for equivalent pier method (Poulos, 1994) C-39
Ratio of load transferred to base to applied load for the equivalent pier method
(Poulos, 1994)
...
C-40 Case 1 : Construction in stiff clay with water table slightly below base of shaft...
G-2 Case 2: Construction in hard clay and shale with layer of waterbearing sand...
G-4 Case 3: Construction in soft and heavily-jointed clays...
G-6 Case 4: Construction in dry sand...
G-7 Case 5: Construction in granular soil below the water table...
G-9 Case 6: Construction through caving soil into sound rock...
G-11 Case 7: Construction through caving soil into fractured rock...
G-13 Case 8: Construction through boulders...
G- 16 Case 9 a: Blocky weathered rock profile (Sowers, 1994)...
G-18 Case 9 b: Construction where the founding rock is vertically slotted...
G-19 Case 10: Construction in karstic regions...
G-21 Case 1 1 : Construction in open water...
G-23 Case 12: Construction through potentially contaminated surface water...
G-25LIST OF TABLES
Table No
.
Title . Page No.
Recommended frequency of borings for drilled shaft foundations for bridges
...
when unclassified excavation is specified (FHWA. 199 1) 28
Geotechnical parameters from borings or soundings to be evaluated numerically if
design procedures in this manual are used
...
.
.
...
30 Brief listing of characteristics of some drilling machines...
78 Mineral sluny specifications for drilled shaft construction in fine sands (modifiedafter Florida Department of Transportation, 1987)
...
.
.
...
144...
Slurry specifications for a rock-socketed drilled shaft (after Holden, 1984) 145 Ranges of properties of various fresh-water slurries at time of concreting
consistent with maintenance of angle of wall friction in sand of 0.67
4
in...
laboratory tests (after Majano et al., 1994) 146
Properties of reinforcing steel for concrete reinforcement
...
164...
Weights and dimensions of deformed bars (Customary) 164
Weights and dimensions of deformed bars (Metric)
...
165 Typical mix proportions for workable drilled shaft concrete (after Sliwinski,1980)
...
189 Concentrations of typical aggressive soil and groundwater contaminants (afterBartholomew, 1980)
...
190 Typical proportions of pozzolanic additives...
19 1 Typical proportions of some prequalified chemical admixtures (extracted fromTXDOT, 1996)
...
192...
Resistance factors,
4,
for selected values of global safety factor, F 242...
Values of I, = E, (Young's Modulus of soil)/3s, and N*, 276
Descriptions of Rock Types for Use in Table 1 1.3
...
277 Values of s and m (Dimensionless) for Equation (1 1.7) based on Classification inTable 1 1.2
...
278 Factors cp for cohesive IGMYs...
.
.
...
283 WES Method of Identifying Potentially Expansive Soils...
309 Minimum Drilled Shaft Penetrations Based on Lateral Loading from theCharacteristic Load Method
...
.
.
.
...
333 Values of Maximum Net Bearing Stresses for Unreinforced Concrete Underreams...
380 Summary of Common NDE Methods for Evaluating Structural Integrity ofDrilled shafts
...
482 Classification of Defects Found in 5000 Drilled Shafts Constructed byCementation Ltd
.
in the United Kingdom in 1982 (Sliwinski and Fleming, 1983)...
505 Possible Acceptance Criteria for Drilled Shafts Constructed Using the WetMethod Where Primary Loading is Axial (Modified After Baker et al., 1993)
...
507 Rating Guideline for Supporting Decisions for Implementation of IntegrityTesting (Modified After Baker et al., 1993)
...
509 ADSC Pricing Survey; Summer, 1997...
532...
Low-Bid Table for Drilled Shafts, Texas DOT, Statewide
...
.
.
534 Low-Bid Table for Drilled Shafts, Texas DOT, District 12 Only...
535Typical Values of COV. 's of Geomateriai Parameters for Drilled Shaft Design
(Modified after Phoon et al.. 1995)
...
A-6...
Load Combinations and Load Factors from AASHTO (1994)...
...
A-18 Load factors (y) for Permanent Loads...
A-19 Notation for Load Components...
A-20 Resistance Factors for Geotechnical Strength Limit State for Axially LoadedDrilled Shafts
...
A-22...
EJ3s, for Cohesive Soil in UU Triaxial Compression and Values of N*, B-13 Values of s and m Based on Rock Classification (Carter and Kulhawy, 1988)
...
B-16...
...
Descriptions of Rock Types for Use in Table B.2 (Hoek, 1983)
....
B-17...
Correction Coefficients for Bearing Capacity Factors (Chen and Kulhawy, 1994) B-22
...
Estimation of Em/Ei Based on RQD (Modified after Carter and Kulhawy, 1988) B-32 f d f , Based on Em& (OINeill et al., 1996) ... B-32 Values of C, is Various Soils (Vesic, 1977)
...
C-3CHAPTER 1 : INTRODUCTION TYPES OF DEEP FOUNDATIONS
The usual role of a deep foundation is to transfer vertical load through weak, near-surface soils to rock or strong soil at depth. Shallow foundations, on the other hand, are frequently used when the surface soils are capable of supporting load without excessive settlement.
There are many types of deep foundations, and classification can be done in various ways. Several of the factors that can be used in classifying deep foundations are given below.
Materials: steel; concrete--plain, reinforced, or pre-stressed; timber; or some combination of these materials.
Methods of transferring load to the soil or rock: principally in end-bearing, principally in skin friction, or in some combination of the two methods.
Influence of installation on soil or rock: displacement piles, such as a closed-ended steel pipe, that displace a large volume of soil as the piles are driven; or nondisplacement piles, such as an H-pile or open-ended steel pipe, that displace a relatively small volume of soil during driving (until the pipe becomes plugged), or drilled shafts, which result in
essentially no displacement of the soil or rock.
Method of installation: impact hammers--hydraulic-, air-, or steam-powered, or diesel-; vibratory hammers; drilling an open hole; or by use of some special method.
Thus, an example of a type of deep foundation is a structural-steel shape (essentially nondisplacement), driven by a diesel hammer to rock, that carries its load in end-bearing.
The drilled shaft is normally used as a deep foundation, but it can also be used as a shallow foundation.
DESCRIPTION OF DRILLED SHAFTS
A drilled shaft is a deep foundation that is constructed by placing fluid concrete in a drilled hole. Reinforcing steel can be installed in the excavation, if desired, prior to placing the concrete. A schematic example of a typical drilled shaft is s h o w in Figure 1.1. The arrows indicate that drilled shafts can carry both axial and lateral loads.
In the United States, the drilled shaft is most commonly constructed by employing rotary drilling equipment to bore a cylindrical hole. The borehole may remain unsupported in soils with
cohesion or in rock, or it may be kept open by using drilling slurry or casing in granular or bouldery soils, occasionally in highly jointed cohesive soil or rock or in very soft cohesive soil.
The casing is usually temporary. It can be placed in a number of ways. After the cylindrical hole is excavated and the casing placed, if necessary, an underreaming tool can be used, if desired, to enlarge the base of a drilled shaft in cohesive soil. A rebar cage can be placed, if needed from a design perspective, and the excavation is filled with fresh concrete. The temporary casing is recovered.
Axial Load
Lateral Load
-
+-- Diameter can vary
I
Reinforcing Steel(Frequently required
/
by design)I
Side ResistanceI
Bell-
May be used or\/
omitted as desired.L
&
Size varies-
no largerthan three times shaft
I t t I t t I
diameter at base. Base ResistanceFigure 1.1. Schematic of a typical drilled shaft
Drilled shafts may also be constructed by the percussion method of excavation. In this case, surface casing is set, and the soil or rock is excavated by a grab bucket, or clamshell. In hard soil or rock, a rock breaker or similar tool can be employed to break the rock before excavation. A rock breaker consists of a heavy bar with a chisel-like tip or a heavy implement shaped like a star
that is dropped repeatedly to fracture the hard soil or rock. An alternate method is to use a harnmergrab, a heavy bucket with sharp point that when dropped will penetrate the geomaterial and can then be used to excavate it without removing the tool and changing to a clamshell.
The borehole for the drilled shaft can be excavated by percussion to make excavations with noncircular cross sections. A surface casing, or guide, in the form of a cross or a rectangle can be placed. The transverse dimensions of the guide will conform to the size of the grab bucket. A
drilled shaft of this type is called a "barrette." Barettes have had little use in the United States during the recent past, except that slurry walls have been excavated with the identical method used to excavate the barrette.
Figure 1.2 shows a typical drilled-shaft construction project in progress. The crane-mounted machines are making the excavations, and a service crane, which will be used to place the reinforcing cage and to assist in placing the concrete, is shown in the background.
Figure 1.2. A typical construction job in progress (Photograph courtesy of Watson, Inc.) Some deep foundations that are not classified as drilled shafts also involve the placing of concrete in a preformed hole. For example,