Continuous Flight Auger CFA Pile Foundations for Highway Projects

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Continuous Flight Auger (CFA) Pile Foundations
for Highway Projects A Market-Ready Technology
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FHWA NATIONAL GEOTECHNICAL PROGRAMWhat Can we
do for you?

• www.fhwa.dot.gov/engineering/geotech

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Course Update.

• NHI 132012
• Soils and Foundations Workshop

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132012 Soils and Foundations

• Recently completed a major update of the manual
  and course slides for the Soils and Foundations
  Workshop
• Publication finalized in December, 2006 and the
  pilot for the course was successfully completed
  during the week of December 11, 2006 (Baton
  Rouge, LA)
• Still to complete Final course slides and
  Instructors Manual
• Materials completely overhauled!

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NEW ADDITIONS

• Chapter 2 Stress and Strain in Soils
• Introduce basic phase (weight-volume)
  relationships
• Effect of size/shape of particles
• Effect of water on physical states
• Principle of effective stress
• Vertical stress distribution under load and DOSI
• Load deformation process
• Lateral stresses in soil
• Shear strength of soil
• Lateral earth pressure

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NEW ADDITIONS

• Chapter 10 Earth Retaining Structures
• Classification and wall selection
• Lateral earth pressures
• Calculation of
• Effect of water
• Effect of surcharge loads
• Design of walls (step-by-step procedure)
• Surface/subsurface drainage

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PRESENTATION CHANGES

• Construction Inspection/Monitoring
• Previously a stand-alone chapter that focused
  solely on pile driving, pile load testing and
  embankment instrumentation.
• Updated to include construction inspection
  information on all geotechnical aspects covered
  in manual.
• Included with respective chapter as a part of the
  discussion of that feature.

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MAJOR UPDATES

• Chapter 3 - Subsurface Explorations
• Expanded discussion on landforms
• Inclusion of CPT as a primary exploration tool
• Section on geophysical testing
• Chapter 4 Engineering Characteristics
• Expanded discussion on description,
  classification and characteristics of rock

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MAJOR UPDATES

• Chapter 5 Laboratory Testing
• Section added on Quality Assurance
• Inclusion of correlations for common parameters
• Permeability testing
• Volume change (swell potential/collapse/frost
  action)
• Compaction of soils
• Laboratory vs. field
• Engineering characteristics
• Laboratory testing of rock
• Elastic properties of soils and rock
• Guidelines for laboratory testing

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MAJOR UPDATES

• Chapter 6 Slope Stability
• Infinite slope analysis
• Recommended stability methods and safety factor
  discussion
• Use of stability charts
• Preliminary design of RSS (improving embankment
  stability)
• Chapter 7 Approach Roadway Deformation
• Better discussion on internal vs. external
  deformation
• Discussion on secondary compression
• Better discussion on lateral squeeze

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MAJOR UPDATES

• Chapter 8 Shallow Foundations
• Inclusion of a discussion on general approaches
  to foundation design
• Foundation alternatives and cost evaluation
• Loads and limit states
• Bearing capacity sections re-written to better
  align with AASHTO 2006 Interims
• Recommendation of Schmertmanns modified method
  for immediate settlement
• Improved section for spread footings on compacted
  structural fills
• Spread footings on IGMs and rock
• Effect of deformation on bridges
• Tolerable movements/Construction point concept

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MAJOR UPDATES

• Chapter 9 Deep Foundations
• Expanded section on drilled shafts and better
  balance with driven piles
• Driven piles section re-written to better align
  with updated Driven Pile Manual
• Inclusion of screen shots for discussion on use
  of DRIVEN computer program
• Expanded sections on static load testing, O-Cell
  and Statnamic testing.

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What did we lose?
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CFA PILES - INTRODUCTION AND TECHNOLOGY OVERVIEW
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Why Continuous Flight Auger (CFA) Pile
Foundations?

• FHWA Interest is due to
• An increase in successful projects in the U.S.
  private sector and in other countries
• Cost effective and more efficient in many
  circumstances
• Fits with Agency Priorities

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New Highway Bill

• Safe, Accountable, Flexible, Efficient
  Transportation Equity Act A Legacy for Users
  (SAFETEA-LU) signed into law in August, 2005
• Includes funding for Highways for L.I.F.E.
  Pilot Program
• Long Lasting Highways using
• Innovative Technologies and Practices to
  Accomplish
• Fast Construction of
• Efficient and Safe Pavements and Bridges

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Infrastructure Research and Development

• The Bridge of the Future
• 100-year service life with minimal maintenance
• A fraction of the current construction time
• Immunity to flooding, earthquakes, fire, wind,
  fracture, corrosion, overloads and vessel
  collision
• Entire bridge from foundations to parapet
  designed and constructed as a system
• Constructability as important as durability
• Expand to include rehabilitation and methods
• Emphasize minimize impact on traveling public

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Current FHWA Activities with CFA Piles

• Publications
• Geotechnical Engineering Circular No. 8 on Design
  and Construction of Continuous Flight Auger Piles
• 2004 TRB Session Proceedings Recent
  Experiences Advancements in the US and Abroad
  on the Use of Auger Cast-in-Place Piles.
  FHWA-RC-BAL-04-003
• Future TRB Sessions to Launch GEC 8
• 2002 International Scan Tour Follow-up
• Promoted by FHWA Office of Infrastructure as a
  Market-Ready Technology

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FHWA Implementation Activities

• Technology Deployment
• Column Supported Embankments
• Structure Foundations
• Sound Wall Foundations
• Lateral Earth Support
• Research
• Design Methodologies
• QA/QC
• Technology Transfer
• Project Based Training

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What is a CFA pile?
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A Continuous Flight Auger (CFA) Pile is

• Any foundation element formed by rotating a
  hollow-stem auger to a desired depth, or until
  refusal criteria is met
• At depth, grout or concrete is pumped under
  continuous pressure through the hollow stem as
  the auger is steadily withdrawn
• Reinforcing steel is placed in the hole once the
  auger has been withdrawn
• This includes traditional continuous flight auger
  piles, drilled displacement piles and partial or
  intermediate displacement piles

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Courtesy of Bauer
Schematic of CFA Pile Construction
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History of Augered Piles

• Development of Auger Cast-in-Place (ACIP) piles
  in US dates to 1940s
• First patents applied for in 1951 granted in
  1956
• 1950s saw development of grout pumps capable of
  pumping coarse sands and hydraulic powered
  systems
• Led to increases from original maximum depths
  (20 ft) and diameters (12 in)
• Today, piles have been installed to depths of
  more than 130 ft at diameters of 36 to 48 in.

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Transportation Applications

• Bridge Foundations Including Abutments
• Retaining Structures (Secant or Tangent Pile
  Walls)
• Column Supported Embankments over Soft Ground
• Sound Walls

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Bridge Foundations including Abutments
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Retaining Structures (Secant or Tangent Walls)
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Column Supported Embankements
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Sound Walls
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Advantages

• Economy and speed
• Does not produce excessive noise or vibration
• Can operate in restricted space and low headroom
  areas
• High production rates typically on the order of
  1000 1500 ft/day in private applications (500
  ft/day expected for transportation applications)

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Limitations

• With US systems, success is highly operator
  dependant
• Drilling resistance does not provide a direct
  indication of soil strength or stiffness
  (research being done in this area)
• Mining and soil decompression can occur in some
  soil types
• Difficult to advance through cobbles or boulders

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Geotechnical Conditions Affecting CFA Pile Use

• Favorable Conditions
• Medium to very stiff clays
• Cemented sands and weak limestone
• Residual soils
• Medium dense to dense silty sands and well-graded
  sands
• Unfavorable Conditions
• Very soft soils
• Loose sands or very clean sands below groundwater
  table
• Karst terrains or highly variable conditions
• Hard/stiff soils overlain by soft soils/loose
  granular soils
• Rock or very hard strata
• Deep scour or liquefiable sand layers

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There Must Be Technical Concerns or Issues!
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Some Concerns We Are Addressing

• There is no nationally accepted design protocol
  for ACIP/CFA piles
• There is no national guideline specification
  which addresses the materials and methods of
  construction
• Quality control and assurance measures must be
  enhanced
• Specifications should give clear guidance for
  pile acceptance and rejection criteria

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Some Technical Issues We Are Addressing

• Cage Installation and Minimum Cover
• Installation Control (soil mining)
• Inspection
• Frequency of Load/Integrity Testing
• Grout/Concrete Strength
• Soft Ground Installation
• Seismic Design
• Structural Design

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Cage Installation (Minimum Cover)
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Cage Installation (Full Depth)
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Installation Control (Soil Mining)
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Installation Control (Pile Finishing)
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Installation Control (Pile Finishing)
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FHWA Development of Guidance on CFA Piles

• Geotechnical Engineering Circular (GEC) 8 is
  complete!
• Development fostered by several issues and
  concerns identified regarding design and
  construction of CFA piles for highway projects
  including
• Minimum equipment requirements
• Penetration rates and control during drilling
• Specific recommendations for problem resolution
• Guidance for verification testing of piles
• Difficulties in contracting/development of
  specifications

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GEC 8 Whats In It?

• Construction Techniques and Materials
• Guidance on Design Process
• Initial design considerations
• Pile design and constructibility
• Preparation of plans and specifications
• Quality Control/Quality Assurance Procedures
• Construction monitoring
• Verification testing
• Load testing
• Integrity testing
• Contracting Methods
• Appendix
• Design examples
• Evaluation of static capacity methods

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PILE TYPES, EQUIPMENT AND BASIC MECHANISMS
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CFA Pile Types

• Auger Cast-in-Place (ACIP)
• Continuous Flight Auger (CFA)
• Drilled Displacement (DD)
• Berkel Displacement Pile (Berkel US)
• DeWaal Pile (Morris-Shea Bridge Company US)
• Omega Pile (L.G. Barcus Sons US)
• Fundex/Tubex (IHC Holland)
• Atlas Screw Pile (Franki/Keller Austrailia)
• Starsol Pile (Soletanche Bachy France)

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ACIP Piles

• Predominantly US system/terminology
• Consists of crane supported swinging or fixed
  leads
• Generally fastest installation time
• Typical pile diameters range from 12-24 inches
  and depths up to 100 feet
• Typical design loads of up to 150 tons in private
  sector applications

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Typical ACIP Pile Rig
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Typical ACIP Pile Rigs
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CFA Piles

• Predominantly European terminology
• Mast driven equipment (similar to drilled shaft
  rigs)
• Equipment provides higher torque at lower rpm
  than ACIP equipment (better control)
• Concrete typically used as opposed to grout
• Can install to larger diameters than ACIP piles
  typically 24 to 36 inches (specialty piles up to
  54 inches)

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Typical CFA Pile Rig
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Drilled Displacement Piles

• Displace soils laterally produce minimal spoils
• Less decompression of soil due to pile
  installation
• Comparable load capacities with shorter, smaller
  diameter piles in certain soil conditions
• Many different types of equipment available (full
  and partial displacement) worldwide to develop
  displacement piles

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• Crawler mounted fixed mast drill rig
• Minimum torque of 150,000 ft-lbs

• Minimum crowd of 25 tons
• Grout pumping similar to crane-mounted ACIP pile

Drilled Displacement Pile Rig (Berkel)
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Partial Displacement
Full Displacement
Drilled Displacement Pile Rigs (Berkel)
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Drilled Displacement Pile Rig (DeWaal)
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Drilled Displacement Pile Rig (Omega Screw)
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Drilled Displacement Pile Rig (Fundex/Tubex)
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Drilled Displacement Pile Rig (Atlas Screw)
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Drilled Displacement Pile Rig (Screwsol)
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Drilled Displacement Pile Rig (Menard CMC)
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Drilling Tools and Equipment
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Augers and Drilling Tools
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Auger Cleaning
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Auger Plug

• Generally made of steel or other hard material.
  If the discharge point of auger is off-center,
  plug may be cork or plastic
• Can be attached or reusable
• Primary purpose is to prevent soil from entering
  auger stem prior to grout or concrete placement
• In some cases (stiff clays, difficult drilling),
  compressed air has been used in lieu of a plug to
  facilitate auger penetration

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Plug at Bottom of Auger
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Disposable Plugs for Bottom of Auger
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Pumping Equipment

• Positive displacement pump capable of delivering
  up to 350 psi of pressure
• Typically, grout pumps operate with reciprocating
  pistons (up to 1 cf per stroke)
• Most important to select pumps for the size of
  pile being constructed (delivers volume per
  stroke of approximately 4 inches of pile length)

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Grout/Concrete Pumps
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Grout/Concrete Pumps
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Finishing the Top of Pile

• Critical item for completion of an acceptable
  pile
• Once concreting is complete and the auger is
  withdrawn, laborers must work to clean the top
  of the pile and protect the pile from fall in of
  surrounding soil
• Typically, contractors will use some type of form
  to case the top of the pile once the excess grout
  and soil have been removed
• Laborer will then scoop the pile to remove
  contamination in the uppermost portion of the pile

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Finishing the Pile Top
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Grout and Concrete

• Both have been successfully used for the
  construction of CFA piles. For CFA piles, grout
  is similar to concrete except that the mix does
  not have coarse aggregate, only sand
• Mixes typically contain Portland cement, fly ash,
  water, and aggregate/fine aggregate
• May see water reducers, fluidifiers, or retarders
  for various purposes
• Use of grout or concrete in CFA pile construction
  has generally been personal preference

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Grout vs. Concrete

• Advantages of grout relative to concrete
• Tends to be more fluid and have better
  workability
• Tends to be easier to pump (especially with
  certain equipment
• Easier insertion of reinforcing steel
• Disadvantages of grout relative to concrete
• Generally more expensive unit cost
• Will tend to have a slightly lower elastic
  modulus
• Will be less stable in the hole (especially in
  soft soils)
• More susceptible to small variations in water
  content (leading to segregation or excessive
  bleed water)

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Reinforcing Steel

• Typically similar to what would be specified for
  drilled shaft construction (ASTM A615 Grade 60
  steel)
• Occasionally may see steel pipe (large bending
  stresses), or high-strength threaded bars (large
  tensile loads)
• Cages normally specified with 3-inch cover. If
  single bars are used, centralizers are normally
  used for centering
• If splicing is required, mechanical is preferred
• Key is working quickly to place steel once auger
  is withdrawn from hole

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Reinforcing Steel Installation
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Reinforcing Steel Installation (Splice)
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Reinforcing Steel Installation
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STATIC CAPACITY OF CFA PILES
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FHWA GUIDANCE

• Based on evaluation of comparative studies of
  numerous methods identified in literature
• Method of installation supports assumption that
  static capacity of a well constructed CFA pile
  lies between drilled shafts and driven piles
• Reasonable to estimate static capacity using
  methods developed specifically for each since
  load-settlement behavior is similar
• Design in practice has used both driven pile and
  drilled shaft approaches
• Drilled shaft approaches favored by most
  practitioners

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FHWA Guidance

• Recommended design guidance based on Allowable
  Stress Design (ASD) for geotechnical conditions.
  Structural pile design is in accordance with LFD
• Recommended that CFA piles be designed with a
  factor of safety of at least 2.5. A factor of
  safety of 2.0 may be used provided the following
  conditions
• At least one static load test to failure
• Automated monitoring is used on production piles
• Relatively consistent geology, stratigraphy and
  soil properties
• Suitable site conditions for construction

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Development of Axial Resistance

• Total Axial Compressive Resistance
• RT RS RB
• Total Side Resistance
• RS S fs,i p Di Li
• Total End Bearing
• RB qp p D2/4

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Development of Axial Resistance

• Side shear component is mobilized with relatively
  small vertical displacement (less than 0.4
  inches)
• End bearing component is mobilized at larger
  displacements (load at 5 displacement of pile
  diameter defined as ultimate)
• Load-settlement curves will typically appear
  softer than for a driven pile (considered when
  evaluating load test data)
• Refer to Reese and ONeill (1988) for assessing
  mobilized side and end bearing resistance under
  load

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Comparison of Static Methods

• Several comparative studies have evaluated the
  ratio of measured to predicted total capacity
  using different methods
• Prediction methods compared to one another using
  mean and standard deviation of capacity ratio
• Failure defined as load at a displacement of
  either 5 or 10 of the pile diameter
• Recommended design procedures appear to provide
  good overall correlation to CFA pile capacity for
  generalized soil types in US Practice
• Alternate methods are discussed for special
  conditions and prediction using in-situ tests

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Recommended Design Methodology Cohesive

• FHWA (1999)

Qult (pDL)fs (p/4)D2qp
Side Shear fs a Su
a 0.55 Su /Pa lt 1.5
a varies linearly from 0.55 0.45 1.5 lt Su /Pa
lt 2.5
End Bearing qp Nc Su
Nc 9 2 tsf lt Su lt 2.6 tsf, and L gt 3D
Nc adjusted for Su lt 2 tsf and L lt 3D
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Recommended Design Methodology Cohesionless

• FHWA (1999)

Qult (pDL)fs (p/4)D2qp
Side Shear fs K sv tan f b K tan f Limited
to 0.25 lt b lt 1.2
b 1.5 0.135 Z 0.5 N60 gt 15 bpf
b (N60 /15)(1.5 0.135 Z 0.5) N60 lt 15 bpf
End Bearing qp (tsf) 0.6 N60 for 0
lt N lt 75 qp 45 tsf for N gt 75
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Recommended Design Methodology DD Piles

• Based on evaluation of load test database from 19
  sites around the US (NeSmith, 2002)
• Failure defined as displacement of 1 inch of tip
  movement or a loading curve displacement rate of
  0.02 in/ton
• Drilled displacement pile correlations should be
  used with caution since these rely heavily on the
  experience of the contractor and must be verified
  for the specific site and equipment

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Recommended Design Methodology DD Piles

• NeSmith (2002)

Qult (pDL)fs (p/4)D2qp
Side Shear fs 0.01 qc Ws for qc lt
200tsf fs 0.05 N60 Ws for N60 lt 50 Ws
0 fs lt 1.7 tsf for uniform rounded sands, lt40
fines Ws 0.5 tsf fs lt 2.2 tsf for well-graded
angular sands, lt10 fines
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Recommended Design Methodology DD Piles

• NeSmith (2002)

Qult (pDL)fs (p/4)D2qp
End Bearing qp 0.01 qc WT for qc lt 200tsf
qp 0.05 N60 WT for N60 lt 50 WT 0 fs lt
75 tsf for uniform rounded sands, lt40 fines WT
0.5 tsf fs lt 85 tsf for well-graded angular
sands, lt10 fines
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Additional Information on Design Methodologies

• Guidance for static capacity of end bearing piles
  on rock and in intermediate geomaterials
• Guidance for laterally loaded piles
• Guidance for pile groups
• Design for uplift and piles in tension
• Structural design of piles
• Design for settlement

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Typical Ultimate Axial Compression Loads
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Typical Ultimate Lateral CFA Pile Capacity
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Typical Capacity and Cost Estimation

• Rule of Thumb (CFA Piles in US)
• Capacity Estimation
• Qall (Pile Area)(1 ksi) - For 4000 psi
  strength grout
• 16 inch pile 100 tons
• Cost Estimation
• Cost 1/inch of pile diameter (per linear foot)
• 16 inch pile 16/l.f.

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Quality Control/Quality Assurance
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FHWA Guidance

• CFA piles have been under-utilized in
  transportation projects due to perceived
  difficulties in quality control
• In addition, the variety in available equipment
  and proprietary systems do not fit easily into
  traditional design-bid-build contracting
• FHWA has developed a performance based
  specification to allow contractors to find the
  most cost-effective solution for project
  requirements
• QC/QA requirements developed with necessary
  performance based measures as the end product

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Why Performance Specifications for CFA Piles?

• Ease in facilitating deployment and
  implementation of new technologies in
  transportation projects
• Provide a contracting method that can incorporate
  the different equipment and proprietary systems
• In the bigger picture, public works projects are
  moving toward more innovative contracting methods
  for development of projects
• Has precedence for successful implementation
  described in FHWA Publication No. FHWA-SA-97-070

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Types of Piles and Installation Methods
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Performance-Based Specifications

• Contractor responsible for pile design (final
  determination of pile length)
• Performance criteria must be established by the
  owner and met by the contractor
• Criteria need to be quantifiable and must be
  measured to provide a reliable indication of
  performance

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Test Pile Program

• Testing
• Pre-production test pile program
• Automated monitoring required
• Integrity Testing
• Verification testing

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• Pre-production test pile program sets criteria
  for production piles
• Establish target drilling penetration rates
• Establish pressure/volume relationships for
  grouting
• For DD piles, establish targets for torque and
  crowd
• Establish/verify mix design parameters
• Evaluate static design correlations

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Conformance Testing

• Integrity testing
• Load testing
• Materials testing

Access Tubes for CSL Testing
Testing with Statnamic (Rapid Load Test) Device
Sonic Echo Testing
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Inspection Responsibilities During Construction

• Pile location/elevation/tolerances
• Grout/concrete monitoring
• Subsidence or lost grout
• Pile completion (screening etc.)
• Reinforcement placement
• Grout/concrete return depth
• Grout Volume

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Monitoring During Drilling

• Monitoring of drilling phase of installation to
  ensure
• No excessive flighting of soil occurs
• Appropriate level of soil displacement occurs
  with DD piles
• Penetration rates are in accordance with test
  program installation rates
• General Guidelines for Penetration Rate for CFA
  Piles

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Monitoring During Drilling

• Private practice has typically monitored
  penetration rate manually by direct observation
  of the auger leads and stopwatch time
• This is not sufficiently accurate for
  transportation work and should not be used as the
  primary means of monitoring drilling
• Automated monitoring systems should include a
  depth encoder and revolution counter such that
  the rate of penetration can be displayed to the
  operator
• In mixed profiles, higher penetration rates
  should control drilling to reduce possibility of
  excessive flighting of soils

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Effects of Over-Excavation During Drilling
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Difficult Drilling Conditions for CFA Piles
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Monitoring During Grouting/Concreting

• The Deep Foundations Institute Augered
  Cast-In-Place Piles Manual (2003) Section 1.3 -
  The grout volume placed for each increment of
  depth is the single most important installation
  control used during ACIP pile construction.
• Grout volume is the most important and most
  difficult inspection item

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Use of Automated Monitoring Equipment

• Manual inspection of grout volume is difficult
• Grout volume usually measured by counting pump
  strokes
• Stroke volume calibrated with 55 gallon drum
• Hard to accurately determine grout pumped versus
  depth increment, and in many cases this results
  in measurement of overall volume only
• Lifting speed and depth of the auger are
  controlled by feel and observation auger height
  in the leads
• The pump does not always maintain a repeatable
  volume per pump stroke
• Well conditioned pumps operating well during
  construction will have up 10 missed or bad
  strokes
• Lead to gross overestimations of grout/concrete
  take

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From PIR-A pressure - 229 good strokes (plus 20
bad) Inspector counted 246 strokes (7 high)
109
B
A
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Monitoring During Grouting/Concreting

• Recommended that the following elements of the
  grouting/ concreting operation be monitored by
  automated system
• Position of the auger tip (depth encoder)
• Volume of grout (in-line flow meter)
• Grout/concrete pressure (pressure gauge)
• Rotation of the auger
• Lifting speed (operator controlled based on above
  controls)

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Automated Monitoring Equipment

• European industry requirements for QA/QC have led
  to the development of sophisticated computer
  based monitoring systems
• The systems now record every detail of the
  augering and concreting operations of each pile
• US systems not as sophisticated yet. Designed for
  adaptability to existing ACIP equipment

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• Measures
• Location of auger tip
• Auger torque
• Grout volume (magnetic flow meter)
• Display of actual vs. target

Developed by Pile Dynamics, Inc.
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Typical PIR Readout From Pile Dynamics, Inc.
114
Developed by Jean Lutz, SA

• The system controls
• Auger rotation speed
• Advancing speed
• Speed/torque settings on the rotary table
• Pressure and the delivery of the concrete
• Extraction speed

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Finishing the Pile

• Completion of the pile top and installation of
  reinforcing steel are not activities that will be
  monitored by automated systems
• Inspection responsibilities for finishing the
  pile top include
• Noting the point at which grout first appears at
  the surface
• Ensuring that volume of grout remains consistent
  once grout is vented at the surface
• Observe screening or dipping of the top of the
  pile to ensure removal of any contamination

116
Additional Inspection Issues

• Reinforcing Steel
• Inspection should concerned with size and
  dimensions of steel, final depth of reinforcement
  and cover
• Sampling and Testing of Grout/Concrete
• Inspection should be concerned with strength and
  workability of the grout or concrete

117
Verification Testing

• Integrity Testing
• LS (PIT) Light Hammer Impact
• HS (PDA) Heavy Ram Impact
• CSL Cross-Hole Ultrasound w/ 2 or more tubes
• SHSL Ultrasound single tube
• Load Testing
• Dynamic Heavy Ram Impact (WR 1-2 of Load)
• Rapid Statnamic Pseudostatic (5-10)
• Static Top Loaded (100)

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SPECIFICATIONS FOR CFA PILES
119
FHWA CFA Pile Guideline Specification

• Performance based to address several issues
  identified earlier in this presentation
• Owner develops design loading criteria and
  performance requirements for foundation elements
• Contractor provides individual pile design and
  selects means and methods for installing piles

120
FHWA CFA Pile Guideline Specification

• Highlights of the specification include
• Design and construction submittals
• Materials and mix design (grout or concrete)
• Protection of adjacent structures
• Grout or concrete sampling and testing
• CFA pile equipment and installation
• Acceptance and rejection criteria
• Inspection records
• Verification testing

121
Design and Construction Submittals

• Prior to construction, contractor will provide
  (not all-inclusive)
• Design calculations
• Design criteria and parameters
• Safety factors
• Design calculation sheets
• Any design notes
• Working drawings
• Plan, elevations and cross sections
• Pile locations and spacing
• Typical pile sections
• Construction sequencing
• Details, dimensions and schedules for piles
• Details for verification testing

122
Design and Construction Submittals

• Prior to construction, contractor will provide
  the following construction submittals
• Pile Installation Plan
• List and sizes of proposed equipment
• Step by step installation procedures
• Target drilling and grouting parameter
• Mix designs, AME procedures, contigency plans
• Conformance testing plan
• Preproduction tests
• Production load testing
• Integrity testing

123
Grout or Concrete Mix Design

• Grout
• Workability test for fluid consistency using
  modified flow cone test
• Shall not exhibit shrinkage in excess of 0.15 in
  vertical direction (ASTM C 1090)
• Must achieve minimum compressive strength
• Mix design will include viscosity loss vs. time
  curves
• Mixes with flyash, silica fume or slag will
  include strength development vs. time curves
• Samples should be 2-inch cubes and subjected to
  10 increase in required compressive strength
  than cylinders

124
Grout or Concrete Mix Design

• Concrete
• Workability slump testing in accordance with
  ASTM C 143
• Must achieve minimum compressive strength
• Mix design will include viscosity loss vs. time
  curves
• Mixes with flyash, silica fume or slag will
  include strength development vs. time curves
• Samples should be 6 in by 12 in cylinders, or
  sized appropriately for the maximum aggregate
  size (ASTM C 39)

125
Auger Equipment

• Auger flights shall be continuous from the top of
  the auger to the bottom tip of the cutting face
• Gaps at joints between auger sections shall be
  less than 1 inch
• Auger flighting diameter shall be uniform and
  outside diameter shall be at least 97 of the
  design pile diameter
• Injection port shall be fitted with a means of
  sealing against ingress during drilling
• Leads should be clearly marked along length to
  facilitate inspection during drilling and grouting

126
Drilling

• Adjacent piles within 6 diameters shall not be
  installed until grout in first pile has set and
  will not be compromised
• Auger shall be advanced into the ground at a
  continuous rate and such that excess soil is not
  flighted to the ground surface
• Pile termination (and/or refusal) criteria shall
  be established during test pile program. Once
  reached, rotation of the auger should be stopped

127
Grout/Concrete Placement

• Placement of grout or concrete should commence
  within 5 minutes of auger reaching planned depth
• At start of pumping, auger shall be raised 6 to
  12 inches to facilitate removal of plug. Once
  grouting has started, auger shall be re- inserted
  to original depth
• Auger pull shall be at a smooth, steady rate
  while continuously pumping. If any rotation of
  the auger occurs, it shall be in the same
  direction as drilling
• Volume measurements will occur as a function of
  depth and will be recorded at intervals of not
  more than 2 feet

128
Grout/Concrete Placement

• Auger withdrawal and pumping will be coordinated
  to maintain positive pressure at the auger tip
• Typical grout volume factors will range from 1.15
  to 1.2. Factors greater than 1.5 may indicate a
  problem
• Volume factor for any pile should be within 7.5
  of the target volume factor
• If grouting is suspended for any reason, the pile
  is deemed unacceptable and will need to be
  re-drilled

129
Testing

• FHWA is currently recommending the following
• Verification testing on a minimum of 2 of
  production piles, or as required by the Engineer
• Integrity testing on a minimum of 20 of
  production piles

130
Rejection Criteria

• Conditions for unacceptable piles
• Failed integrity testing
• Failed load test
• Automated monitoring or project inspection
  indicates an inadequate pile (does not meet test
  program criteria)
• Pile out of tolerance (plan or elevation)
• Grout/concrete strength or volume factor
  inadequate
• Reinforcing steel not inserted as designed
• Visual evidence of contamination, excessive
  settlement, structural damage, honeycombing

131
Thank You!Silas Nichols, P.E.Geotechnical
EngineerFHWA Resource Center61 Forsyth Street,
SWSuite 17T26Atlanta, GA 30303Phone
404-562-3930Email silas.nichols_at_fhwa.dot.gov