11h00bernardhhertlein18-06.pdf

7/30/2019 11h00BernardHHertlein18-06.pdf

1/22

Integrity Testing of Deep Foundations:A Critical Review of the State of the Art

Bernard H. Hertlein, M.ASCE

SEFE-7, So Paulo, Brazil - June 18, 2012


2/22

Maximizing the Reliability and Benefits

of Integrity Testing

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



3/22

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 CollateralSEFE-7, So Paulo, Brazil - June 18, 2012


4/22

Nondestructive Integrity Test Options:

Impulse Echo (Sonic Echo)

Impulse Response (Sonic Mobility)

Crosshole Sonic Logging

Gamma/gamma Logging

Thermal Integrity Profiling



5/22

Impulse Echo Method

Developed for pre-castdriven piles

Very fast and economical

Only measures lengthNot good in complex soilsor with variable cross-section

Limited penetration depth



6/22

Impulse-Echo Data



7/22

Impulse-Echo Data Amplification



8/22

Impulse Response Method

Measures stiffness, length,

cross-section and concrete

quality

Sensitive to shaft head

condition

Sensitive to surroundingsoils

Not good with multiplereflectors

Limited penetration depth

Hammer with forcetransducer

Geophone

DataAcquisitionSystem



9/22

Impulse Response Spectrum Data



10/22

Crosshole Sonic Log Method

Measures UPV of

concrete

Depth limited only bycables

Good horizontal range

(>10 ft)

Sensitive to tubecoupling to surrounding

concrete

Concrete



11/22

CSL Data Processing



12/22

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 ofcover concrete

Sensitive to joints/ties

000

ConcreteAccess tube



13/22

Reinforcing cage eccentric due to broken or missing centralizers

Dotted circle indicates sphere

of influence of test robe

Nominal data

Data skewed highby proximity of

steel

Concrete

Data skewed low byproximity of soil and

lack of steel

Effects of Cage Eccentricity



14/22

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 shaftsSEFE-7, So Paulo, Brazil - June 18, 2012


15/22

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.



16/22

Providing Access

It is extremely important that the contractor

provides the tester with good, safe access.



17/22

Analysis Collateral

Analysis Collateral is the additional informationthat should be reviewed when analyzing and

interpreting integrity test data. It may include:

Geotechnical exploration boring logs.

Foundation design.

Foundation Inspectors field records.

Contractors daily records & concrete tickets.

Automated monitoring system records.

Concrete mix design.



18/22

Categorizing Anomalous Data:

Whats 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.



19/22

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 orseismic loads?



20/22

Conclusions

If nondestructive integrity test methods are to provide

accurate and reliable data for quality management of

deep foundations, then:

The selected 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 that specific

method and data format, as well as the constructionmethod used.



21/22

Conclusions (continued)

The contractor must cooperate with the tester to

provide safe access and working conditions.

All possible analysis collateral must be madeavailable to the testing firm.

The significance of any reported flaws must bedetermined by the design team after careful

engineering review.

The design engineer and the contractor should

consider if the test results can help improve thedesign and/or the construction procedure.



22/22

Thank You

[email protected]


11h00bernardhhertlein18-06.pdf

Documents