GDL and CSL Integrity Testing for

Cast in Place Drilled ShaftsWhat Do I Do With the Results?

2

Geophysics – Proven Record of Integrity

Testing of Drilled Shafts

Flaws found using GDL

technology in late 1980’s

3

Construction of Drilled Cast in Place

Concrete Shaft Foundations

Drill shaft to specified depth

Insert reinforcing steel

Fill hole with concrete

4

Completed Foundation Shaft

All is Well?

5

Problems with Drilled Shafts?

Can’t See What’s Happening Down Below

6

Latent Defects in Shafts

7

Latent Defects in Shafts

8

Tools Used for Testing

Gamma Density Equipment

Cross-hole Sonic Equipment

9

Cross Hole Sonic Logging (CSL)

Data Collection

Place two probes (sender and

receiver) into two of the PVC

inspection tubes

Lower the two probes to the

bottom of the shaft

Continuously record as probes are

pulled to the top

10

Speed of Sound – Rules of Thumb

Speed of Sound in Different Materials

(ft/sec) (km/sec)

Air 1,100 0.3

Water 4,800 1.5

Normal Concrete 12,000 3.7

11

Historical Data – Velocity vs Strength

6000

8000

10000

12000

14000

16000

0 1000 2000 3000 4000 5000 6000 7000 8000Concrete Unconfined Compressive Strength (UCS), psi

Ult

raso

nic

P-w

ave V

elo

city

, f/

s

110

120

130

140

150

160

Con

crete

Den

sity

or U

nit

Weig

ht,

pcf

.

Samples from Cotton Lane

Bridge core data at 14 day

breaks (AMEC files)

Example P-wave velocity vs UCS for

one batch of one mix design at 12-hr to

7 day breaks (Pessiki and Carrino, 1988)

12-hr breaks

3 day breaks

7 day breaks

1 day breaks

Samples of design mix at 14 day break -

P-wave velocity from laboratory bench

sonic impact echo impulse test on an

I-10 project (AMEC files)

(modified from Rucker and others, 2008)

12

Cross-hole Sonic Logging (CSL)

Test Data

13

Multiple Tube Combinations

1

5

4 3

2

5 Tubes

10 Possible Tube Combinations

4 + 3 + 2 + 1 = 10

14

Cross-Hole Sonic Logging (CSL)

Test Data – 3 Pairs of Tubes

15

CSL Test Results - 3 D Tomography

16

Strength Gain of Concrete Over Time

0

1000

2000

3000

4000

5000

6000

0 5 10 15 20 25 30 35 40

Co

mp

ressiv

e S

tren

gth

, p

si

Age, Days

Compressive Strength Gain Curve

Average Strengths-AMEC 6X12 Cylinders (DS35B) Strength Vs Age Curve-AMEC 6X12 Cylinders (DS35B)

Average Strengths-City of Phoenix Data (DS34A, DS34B, DS35A, DS35B) Strength Vs Age Curve-City of Phoenix Data (DS34A, DS34B, DS35A, DS35B)

Average Strengths-Hypothetical 4000 psi Mix based on City of Phoenix's Data Strength Vs Age Curve-Hypothetical 4000 psi Mix based on City of Phoenix's Data

17

Threshold Wave speeds

Rough Order of Magnitude Correlation of Sonic

Wave speed to Compressive Strength of

Concrete

Wave speed

(ft/sec)

Wave speed to achieve 5,300 psi at 28 days 12,400

Wave speed to achieve 4,000 psi at 28 days 11,400

Wave speed to achieve 1,000 psi at 28 days 8,800

Wave speed in Water – 0 psi 4,800

Wave speed in Air – 0 psi 1,100

18

Project Blue Sky Harbor – Depth of 15 Feet

Low Compressive Strength,

but not Water or Soil

19

Project Blue Sky Harbor – 3D Tomography

It Means This Shaft is Bad at 9 Feet!

20

Gamma Density –

Calibration Test Barrels

21

0

0.5

1

1.5

2

2.5

3

3.5

4

120 130 140 150 160

Density, pcf

Dep

th,

ft

Black pipe "dry"

Black pipe "wet"

Galv pipe "dry"

Galv pipe "wet"

PVC pipe "dry"

PVC pIpe "wet"

Wall thickness:

Galv pipe 0.276 in

Black pipe 0.120 in

concrete

ABC

air

Barrel Bottom

GDL Test Barrel Results

22

What Access Tubes Must Endure

23

Issues in Gamma Density Interpretation

Cotton Lane Bridge Pier-11 Shaft-3 Tube-2

135

140

145

150

155

160

165

0 10 20 30 40 50 60 70 80 90 100 110

Depth (ft)

Den

sity

(p

cf)

Rela

tive

Den

sity

Ch

an

ge (

pcf)

anomaly

~3.8 pcf

-3 st dev - flaw included in calculation

3 st dev - flaw removed from calculation

mean

st dev = 0.93 pcf

st dev = 1.34 pcf

PVC pipe coupler signatures at 15.4, 35.5, 55.5, 74.8 and 94.6 feet

actual

anomaly

exceeds

3 st dev

criteria

without adjustment,

same anomaly moved

to different part of

plot does not exceed

3 st dev criteria

Unadjusted Depth - Density Plot

Adjusted Depth - Density Plot

24

What Happens With Non Conformances

Non Compliant results typically do not

have a clear cut resolution

Similar to finding out the concrete

strength is insufficient 28 days after it

is placed, only worse

Structural engineers and Owners

struggle to understand the results and

will often under- or over-react to them

Contractors seek conclusive evidence

before they undertake expensive

repairs or replacement

25

Solution

Combine CSL and GDL methods to

give better meaning to structural

engineers, owners and contractors

Utilize other test methods such as

Low Strain Integrity, 3D Tomography

and Coring if more clarity is needed

The testing engineer must work in

conjunction with the structural

engineer and the geotechnical

engineer to assess the load carrying

capacity of the shaft

26

Cotton Lane Bridge –

Test Inclusions & Real Anomalies

Tube 1 – foam plug

Tube 2 – 1L bottle

Tube 1 Tube 2

27

Pier 11 Shaft 2

Sandbag anomaly installed

between Tubes 4 & 5 @ 90’

No CSL or GDL response

28

contamination @ 29’

end of core run @31’

soft bottom?

A real anomaly in Pier 11 Shaft 3 –

Initial logging done over holidays after only 1 day cure

29

Dec 06 Feb 07

Dec 06 Feb 07

Flaw Zone evaluated with 7 interior coreholes – cleaned out by pressurized

water, pressure grouted to fill interior void spaces.

No change in GDL

anomaly smaller, soft bottom gone

~3’ ~1’

cured

30

Cutting Tool Uses High Pressure Water

31

Demonstration of Cutting Tool

32

Cutting PVC Inspection Tubes at 30’ Depth

33

Bridge Over Salt River, Phoenix, AZ

pervasive ‘blow in’

core runs to top of ‘blow in’

Anomaly identified throughout CSL & GDL data

Six coreholes verified extent

34

Problem detection and repair completed in 3 weeks, overall

project schedule not impacted!

cleaning & prep for new concrete

Overlapping large diameter coreholes to

access problem area for repair

Repair concrete was placed by gravity with vibration–

zone was cleaned to good concrete with

surfaces sloping upward to not trap air

35

End Slide Show

Questions?