Deep Foundation Testing, Multiple Topics Brent Robinson, Ph.D., P.E. - - PowerPoint PPT Presentation

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Deep Foundation Testing, Multiple Topics Brent Robinson, Ph.D., P.E. - - PowerPoint PPT Presentation

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Deep Foundation Testing, Multiple Topics Brent Robinson, Ph.D., P.E. www.grlengineers.com | info@grlengineers.com www.grlengineers.com | info@grlengineers.com Deep Foundation Testing, Multiple Topics PDA/CAPWAP applied to large diameter

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Deep Foundation Testing, Multiple Topics Brent Robinson, Ph.D., P.E.

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  • PDA/CAPWAP applied to large diameter piles versus small diameter piles
  • PDA/CAPWAP challenges for open ended piles
  • Thermal Integrity Profiling (TIP)
  • How to interpret CSL results for acceptance of shafts; when to

remediate/repair/replace, etc. based on test results

  • Determining capacity and assessing integrity of a damaged pile or drilled shaft

through dynamic testing

  • SPT Analyzer best methods for determining energy transfer of automatic

hammers

Deep Foundation Testing, Multiple Topics

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  • Not a lot of direct comparisons
  • Might need different hammers
  • Sites are variable
  • Test piles are spaced widely apart
  • Getting this type of research going is a big effort
  • Requires the ‘right’ geotechnical conditions, too

Driven--Large vs small diameter

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Driven—Large vs Small Diameter

14” CEP, No Epoxy 24” CEP, Epoxy

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  • Marquette Interchange, Wisconsin
  • 12.75, 14, 16 inch diameter at SLT site
  • Complications
  • Time after driving
  • Mobilization
  • Driving order (pore pressures)
  • Densification
  • Soil displacement
  • Vibration
  • Signal match (CAPWAP) distribution

precisions

Set-up—Large vs Small Diameter

16, 50 d 14 16, 78d 14 12

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  • Scaling is not well understood
  • ADSC research project underway for drilled piles
  • Larger diameter piles likely take more displacement to fully mobilize
  • Can be a challenge with significant set up and inadequately sized hammer
  • Larger diameter piles more likely to also have lower velocities,

different dynamic response

  • Statically, different displaced volumes of soil or plugging behavior

Large vs Small Diameter

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  • Experiences from other attendees

Large vs Small Diameter

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  • PDA/CAPWAP applied to large diameter piles versus small diameter piles
  • PDA/CAPWAP challenges for open ended piles
  • Thermal Integrity Profiling (TIP)
  • How to interpret CSL results for acceptance of shafts; when to

remediate/repair/replace, etc. based on test results

  • Determining capacity and assessing integrity of a damaged pile or drilled shaft

through dynamic testing

  • SPT Analyzer best methods for determining energy transfer of automatic

hammers

Deep Foundation Testing, Multiple Topics

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  • For many years, steel wave speeds constant
  • Past 10 years, PDI clients (GRL, Domestic,

International) noted apparently faster wave speeds on LDOEP

  • Timing of toe reflection was earlier than

expected

  • Different PDA units and models
  • Pile Short? Damage?
  • For restrikes, tough to say!
  • Initial Drives from very first blow confirmed
  • Wave speeds were increasing by 2-3%

Challenge 1: Wave Speed

Property US Wave Speed 16,800 ft/s Unit Weight 492 lb/ft3 Elastic Modulus 30,000 ksi

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  • 42 inch O.D. x 0.75 inch wall (1067 mm x 19 mm), open end

pipe piles

  • ASTM A-252 Grade 3 steel, specified minimum FY = 50 ksi
  • Piles were made from hot rolled black steel coil converted to

spiral weld pipe

  • 70 ft long top section welded to previously driven first section
  • Two PR accelerometers attached 7 ft from top
  • Two additional PE accelerometers attached 71.2 ft from top
  • Distance between PR and PE accelerometers of 64.2 feet

Minnesota

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Minnesota

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  • Dynamic test records on 30 to 48 inch diameter have supported

the need for a 1 to 3% faster overall wave speed.

  • Not PDA unit dependent
  • Multiple Steel Grades, 45 ksi or more
  • Faster overall wave speed greater than 16,800 ft/s may be

justified by early, easy driving records with carefully documented lengths

  • Should not be assumed without early data—might miss pile toe

damage.

  • Faster overall wave speeds have NOT been observed on

smaller diameter steel pipe piles (<24 inch) or hot rolled H-piles.

Challenge 1: Wave Speed

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  • Recent projects in the Midwest
  • Kentucky Lakes, Kentucky
  • Gnadenhutten, Ohio
  • Effect of constrictor plates on

dynamic behavior

  • Modeling in CAPWAP

Challenge 2: Constrictor Plates

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Kentucky Lakes

  • Analysis complicated by constrictor plate, soil plug, pore water pressures
  • Use of radiation damping model
  • Modeling of soil plug
  • Resistance from constrictor plate included in shaft resistance total
  • Superposition of shaft resistance and end bearing used to evaluate

resistance during restrike

  • Under prediction of static resistance possible due to failure mode under

dynamic vs. static load

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Ohio

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  • Brown’s NCHRP Synthesis noted high accelerations
  • n the plug may cause it to slip dynamically but not

statically

  • Constrictor plate models indicated radiation

damping may be a solution

  • Current internal research looks at numerical

models

Challenge 3: Internal Soil

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OUR PLUG MODEL

N-2 N-1 N

Mplug

We add at the bottom segment an interface force representing friction between inside pipe and plug

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And a Plug End bearing in addition to the pile end bearing

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OUR PLUG MODEL

N-2 N-1 N

Mplug

We add at the bottom segment an interface force representing friction between inside pipe and plug

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Challenge 3: Internal Soil

  • Top Displacements
  • Plug End bearing:
  • 662 kips
  • Internal shaft

resistance: 331/662/800/1200 kips

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  • Petek et al (forthcoming) ran database studies
  • Well documented case histories with dynamic, static and

suitable geotechnical studies are hard to find

  • Alpha method correlated reasonably well with static load

tests

  • Beta method was much more scattered
  • Dynamic tests, when available, were not well documented
  • Instrumented static load tests are difficult
  • Sensor survival when welded and protected

Challenge 4: Comparison Data

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  • PDA/CAPWAP applied to large diameter piles versus small diameter piles
  • PDA/CAPWAP challenges for open ended piles
  • Thermal Integrity Profiling (TIP)
  • How to interpret CSL results for acceptance of shafts; when to

remediate/repair/replace, etc. based on test results

  • Determining capacity and assessing integrity of a damaged pile or drilled shaft

through dynamic testing

  • SPT Analyzer best methods for determining energy transfer of automatic

hammers

Deep Foundation Testing, Multiple Topics

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Cloud

TAG – Thermal AGgregator

  • TAG doubles as TAP box for data

collection

  • Wireless System aggregates

information from TAP boxes to the TAG

  • Data sent to the Cloud via wireless

modem

  • Data retrieved in office via internet

connection (user password protected)

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350 Foundation Shafts (48 inch dia.)

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6 – number completed when problem

noted (groundwater washed out concrete for all 6 piles when casing was pulled)

Construction technique was corrected

85 - number completed when CSL testing

is normally made (7 days)

120 - number completed when report is

normally issued (10 d)

Center  @ cage

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Recommended TIP Criteria

Satisfactory (S)

< 6% Radius Reduction and Cover Criteria Met Anomaly requiring further Evaluation (E) Radius Reduction > 6% or Cover Criteria Not Met

(a uniform 6% reduced radius is a 12% area reduction and a 22% bending capacity loss)

minimum cover – 4 inch - AASHTO minimum cover – 3 inch - ACI Need larger design cover to allow for cage eccentricity so net cover is sufficient

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36 hours 1.5 days “Peak”

Wisconsin Project

18 hours 0.75 days

Perimeter Main Diagonal

19oF vs peak 13oF vs peak Pile cored: “Good, clean concrete above and below a 6 inch void” (Due to tremie problem)

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Early local temperature reduction.

2 hours 4.5 hours 8 hours 18 hours

Thermal Integrity Profiling

Tell very early if shaft is OK or defective

Wisconsin Project

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4 ft diameter shafts - Michigan first shaft second shaft

bad good

4.5’ dia 4’

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4 ft dia – cast June 5 TIP 1 day, CSL 2 day

bad bad

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Pile 7 - TIP vs PIT – 10.75 inch micropile

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Shaft Verticality and Profile Shaft Base Cleanliness Bi-Directional Static Load Test Thermal Integrity Profiling (TIP) Crosshole Sonic Logging (CSL) Weighted Tape

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Shaft Verticality and Profile

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Shaft Verticality and Profile Results

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  • 34
  • 32
  • 30
  • 28
  • 26
  • 24
  • 22
  • 20
  • 18
  • 16
  • 14
  • 12
  • 10
  • 8
  • 6
  • 4
  • 2

2 4 6

  • 1.6
  • 1.2
  • 0.8
  • 0.4

0.0 0.4 0.8 1.2 1.6 Elevation (m) Radius (m)

TIP SHAPE Concrete Volume Theoretical

Comparison

  • f

Shaft Radius vs Elevation

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SQUID Results

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Bi-Directional Test Results

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5

  • 70
  • 65
  • 60
  • 55
  • 50
  • 45
  • 40
  • 35
  • 30
  • 25
  • 20
  • 15
  • 10
  • 5

Unit Base Resistance, qBASE, MPa Total Base Resistance, QBASE, MN Base Displacement, zBASE, mm

  • Fig. 10: Harbor River Bridge - Beaufort County, SC - Test Shaft TS-1 -

Total and Unit Base Resistance vs. Base Displacement (QBASE-zBASE, qBASE-zBASE)

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Michigan

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  • PDA/CAPWAP applied to large diameter piles versus small diameter piles
  • PDA/CAPWAP challenges for open ended piles
  • Thermal Integrity Profiling (TIP)
  • How to interpret CSL results for acceptance of shafts; when to

remediate/repair/replace, etc. based on test results

  • Determining capacity and assessing integrity of a damaged pile or drilled shaft

through dynamic testing

  • SPT Analyzer best methods for determining energy transfer of automatic

hammers

Deep Foundation Testing, Multiple Topics

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Good (G)

First Arrival Time (FAT) increase 0 to 10%

Questionable (Q)

FAT increase 11 to 20%

Poor/Defect (P/D)

FAT increase >21%

No Signal (NS)

FAT increase >21%

Traditional rating in USA

Problems: Makes vague reference to “signal amplitude” but no specific guidance “Ratings other than Good (G) will require additional evaluation” (no specific guidance)

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15% 30% 9dB 12dB First Arrival Time Delay Consider actual WS Relative Energy Reduction

Rating Guide Rating Guide

A B C

Terminology and Evaluation Criteria of Crosshole Sonic Logging (CSL) as applied to Deep Foundations (2019)

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Category B (Conditionally Acceptable):

  • 1. Rule out debonding (flood pile top)
  • 2. Retest after longer wait time
  • 3. Desktop evaulation
  • 4. Tomography
  • 5. Consider depth location and # of affected profiles

Proposed guidance Proposed guidance

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PVC tubes “debonding” ? CSL @ 8 days Re-test after remove PVC tubes CSL @ 11 days Better to use steel

  • tubes. Avoid PVC.
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Desktop Evaluation

  • The number of affected profiles, depth and vertical extent
  • f affected zones, and severity
  • Low or high concrete strength (wave speed changes)
  • Construction records
  • Often a very important clue
  • Installation logs
  • Soil information
  • Concrete volume logs
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Tomography

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Category C (Highly Abnormal):

  • 1. Rule out debonding (flood pile top)
  • 2. Retest after longer wait time
  • 3. Tomography
  • 4. Consider depth location and # of affected profiles
  • 5. “More invasive methods”
  • a. Excavation if near ground surface
  • b. Core drilling if deep location

i. Pressure grout

  • ii. Strength test core
  • c. Other test (low strain, high strain PDA)
  • d. Repair or replacement

Proposed guidance Proposed guidance

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Repaired by pressure grouting

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2 month later (after grouting)

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Defect confirmed by a PDA test

PDA sensors not at top of concrete

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  • You need more than the CSL report
  • Installation Logs
  • Casings?
  • Diameter changes?
  • Air/Water/Soil Interfaces?
  • Soils and water encountered
  • Cage changes or congestion?
  • Measurement locations?
  • Internal structural elements? Couplers?
  • Structural Loads and Load Types?
  • Caliper or Bottom Devices?

Interpreting CSL (or TIP) for Acceptance

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  • PDA/CAPWAP applied to large diameter piles versus small diameter piles
  • PDA/CAPWAP challenges for open ended piles
  • Thermal Integrity Profiling (TIP)
  • How to interpret CSL results for acceptance of shafts; when to

remediate/repair/replace, etc. based on test results

  • Determining capacity and assessing integrity of a damaged pile or drilled

shaft through dynamic testing

  • SPT Analyzer best methods for determining energy transfer of automatic

hammers

Deep Foundation Testing, Multiple Topics

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Toe damage

EX-117 24 inch Concrete pile (Ex-117) APE D50-42, LE 91 ft. LP 72 ft. LE 91

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Toe Damage

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  • CAPWAP assumes elastic pile material properties
  • Once concrete is damaged, is it still elastic?
  • Once steel is crumpled, is it elastic?
  • How does it behave if there is a bend?
  • Static load tests are rare on piles with KNOWN damage
  • Therefore, PDI and GRL recommends, in most cases, using shaft

resistance above damage, discounting the rest

  • Open splices with splice plates?

Toe Damage—What to do?

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Toe damage—Pipe to Rock

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  • If modeled as ‘toe quake’
  • Does that adequately capture behavior of a yielded section?
  • We might be able to generally assess apparent section reduction
  • Skyline Steel cites uncertainty when asked about behavior of yielded

sections as well

Toe Damage—Signal Matching

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  • Splice damage indicator, early toe
  • Broken
  • Splice damage indicator, normal toe
  • Partially broken
  • If there is a plate
  • Maybe compression OK
  • Uplift resistance only from upper section
  • Redundancy!

Splice damage

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CAPWAP and TIP on a 2.1 m diameter drilled shaft

TIP Measurements CAPWAP impedance

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  • PDA/CAPWAP applied to large diameter piles versus small diameter piles
  • PDA/CAPWAP challenges for open ended piles
  • Thermal Integrity Profiling (TIP)
  • How to interpret CSL results for acceptance of shafts; when to

remediate/repair/replace, etc. based on test results

  • Determining capacity and assessing integrity of a damaged pile or drilled shaft

through dynamic testing

  • SPT Analyzer best methods for determining energy transfer of automatic

hammers

Deep Foundation Testing, Multiple Topics

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MINNESOTA PRACTICE