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» Fifth levelNondestructive Testing of ACIP & Drilled Displacement Piles

Presented By:

Bernard H. Hertlein, FACI, M.ASCE

GEI Consultants, Inc., Libertyville IL

DFI ACIP & DD Pile Seminar, New York City, NY November 7, 2013

Effective Nondestructive Testing Needs Cooperation

Everyone on the project team has a role to play:

•Geotechnical Engineer – soil information

• Structural Engineer – test specification

•Contractor – construction records & access

•Tester – accurate test results

•Analyst - interpretation

DFI ACIP/DD Pile Seminar, New York City, NY - November 7, 2013

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Factors Affecting the Quality of Integrity Test Data and Interpretation

•Understanding of the capabilities and limitations of each test method.

•Operator training.

•Increased affordability of advanced equipment.

•“Expert” software with automated acquisition and interpretation functions.

•Availability and review of other available information – “Analysis Collateral”


Nondestructive Integrity Test Options:

•Impulse Echo (Sonic Echo)

•Impulse Response (Sonic Mobility)

•Crosshole Sonic Logging

•Gamma/gamma Logging

•Thermal Integrity Profiling


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Impulse Echo Method

• Developed for pre-cast driven piles

• Very fast and economical

• Only measures length

• Not good in complex soils or with variable cross-section

• Limited penetration depth


Impulse-Echo Data


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Impulse-Echo Data Amplification


Impulse Response Method

• Measures stiffness, length, cross-section and concrete quality

• Sensitive to shaft head condition

• Sensitive to surrounding soils

• Not good with multiple reflectors

• Limited penetration depth

Hammer with force transducer

Geophone

Data Acquisition System


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Impulse Response Spectrum Data


Crosshole Sonic Log Method

• Measures UPV of concrete

• Depth limited only by cables

• Good horizontal range (>10 ft)

• Sensitive to tube coupling to surrounding concrete

Concrete


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CSL Data Processing


Gamma/gamma Log Method

• Estimates concrete density

• Depth limited only by cable length

• Limited range (3-4 ins)

• Sensitive to proximity of vertical steel

• Sensitive to thickness of cover concrete

• Sensitive to joints/ties

000

Concrete

Access tube


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Reinforcing cage eccentric due to broken or missing centralizers

Dotted circle indicates sphere of influence of test probe

Nominal data

Data skewed high by proximity of

steel

Concrete

Data skewed low by proximity of soil and

lack of steel

Effects of Cage Eccentricity


Thermal Integrity Profiling

Infrared sensors can be used in CSL or GGL tubes to detect variations in temperature.

Alternatively, strings of temperature sensors can be attached to the reinforcing steel during construction.

The data is analyzed to delineate temperature variation caused by inclusions, lack of cover concrete or reinforcing cage eccentricity.

Limited time window for testing, especially on smaller shafts


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Selecting a Test Program

Each test method has specific capabilities and limitations that must be considered when specifying the integrity testing program.

Additional factors to consider are:

•Foundation type and size.

•Type of information required.

•Construction method.

•Soil conditions.

•Access conditions.DFI ACIP/DD Pile Seminar, New York City, NY - November 7, 2013

Providing Access

It is extremely important that the contractor provides the tester with good, safe access.


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You Want Me To Test What?


Analysis Collateral

Analysis Collateral is the additional information that should be reviewed when analyzing and interpreting integrity test data. It may include:

•Geotechnical exploration boring logs.

•Foundation design.

•Foundation Inspector’s field records.

•Contractor’s daily records & concrete tickets.

•Automated monitoring system records.

•Concrete mix design.DFI ACIP/DD Pile Seminar, New York City, NY - November 7, 2013

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Categorizing Anomalous Data: What’s in a Name?

After Amir, 2001

•Anomaly – an irregularity in the data.

•Flaw – an irregularity in the foundation that does not affect capacity or durability.

•Defect - an irregularity in the foundation that reduces capacity or durability.


Determining Significance

•What is the design load on the shaft?

•Will the shaft work in side friction, end-bearing, or both?

•What is the location and extent of the flaw?

•Is the shaft a single, non-redundant foundation or is it part of a group?

•Will the shaft be subject to lateral or seismic loads?


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Inspection/Monitoring of ACIP & DD Piles

• Always watch auger insertion.

• With ACIP piles monitor the cuttings!

• Count pump strokes.

• Watch rate of auger withdrawal.

• Log depth of grout return.

• Use Automated Measurement Equipment to monitor concrete or grout placement.

• Use “football” spacer on center rebar.


Case History #1 – ACIP Pile with Automated Measurement Equipment

Sonic Echo Test Result


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Impedance Log


Computer Simulation


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Impedance Log From Impulse Data

• Add Simul slide/demo?


ACIP Construction Monitor Report


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Case History #2 – Drilled Displacement Shaft with Automated Measurement Equipment


A Typical Normal Test Result


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Low-Strain Integrity Test Result


The Culprit?


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Case History #2 – Comparison of Low Strain Integrity Test with Thermal Profile

DFI ACIP/DD Pile Seminar, New York City, NY - November 7, 2013 Graphic Courtesy of Pile Dynamics, Inc.

Low Strain Integrity Test versus Thermal Profile


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Case History #2 – Comparison of Low Strain Integrity Test with Thermal Profile


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Conclusions

If nondestructive integrity test methods are to provide accurate and reliable data for quality management of ACIP & Drilled Displacement Piles, then:

• All NDT methods have specific capabilities and limitations - the test method must be appropriate for the site conditions and information required.

• The test operator must be properly trained with that specific method and equipment.

• The analyst must be experienced with both the test method and the construction method used.


Conclusions (continued)

• Nondestructive testing is a supplement to traditional inspection methods, not a replacement.

• Cooperation in preparing and providing safe access to sound concrete is necessary if NDT is to be accurate and efficient.

• Construction information is necessary if interpretation of NDT is to be most accurate - All possible analysis collateral should be available to the testing firm or data analyst.


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Conclusions (continued)

• Any reported flaw should be evaluated by both the geotechnical and the structural engineer to determine it’s likely significance in terms of shaft capacity and durability.

• The design engineer and the contractor should consider if the test results can help improve the design and/or the construction procedure.

• The Contractor and subcontractors should guard against accidental damage from vehicle or equipment impact.



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New Release .PDF on Flash Drive

Guideline For Interpretation of Nondestructive Integrity testing of

ACIP & DD Piles

DFI ACIP & DD Committee

DFI Test and Evaluation Committee


Thank You – Questions?


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