J. Brian

Anderson,

Associate

Professor of

Civil

Engineering

Auburn

University

Database

Evaluation of

Energy Transfer

for CME

Automatic

Hammer Standard

Penetration Tests

October 28, 2014

45th Annual Southeastern

Transportation

Geotechnical Engineering

Conference

Mobile, AL

The Standard Penetration Test

SPT Energy Correction & Measurement

SPT Energy Calibration of ALDOT Equipment

and Operators

Comparison to Large Scale Calibration Study

Conclusions

OUTLINE

The Standard Penetration Test

SPT Energy Correction & Measurement

SPT Energy Calibration of ALDOT Equipment

and Operators

Comparison to Large Scale Calibration Study

Conclusions

OUTLINE

Since ~ 1930.

SPT dates back to Charles Gow of the

Raymond Concrete Pile Company

STANDARD PENETRATION TEST

SPT SPLIT-SPOON SAMPLER

SPT SPLIT-SPOON SAMPLER

(a) (a)

Donut

Hammer

Safety

Hammer From Coduto (1999)

SPT MANUAL/SAFETY HAMMER

SPT AUTOMATIC HAMMERS

Automatic Safety

SPT

Hammer

Drill Rods

The Standard Penetration Test

SPT Energy Correction & Measurement

SPT Energy Calibration of ALDOT Equipment

and Operators

Comparison to Large Scale Calibration Study

Conclusions

OUTLINE

CORRECTIONS TO SPT N-VALUE

Nmeasured = Raw SPT Resistance (ASTM D 1586)

N60 = (ER/60) Nmeasured = Energy-corrected N value where

ER = energy ratio (ASTM D 4633).

Note: 30% < ER < 100% with average ER = 60% in the U.S.

N60 = CE CB CS CR Nmeasured Estimated corrected value

(N1)60 = CN N60 = Energy-corrected SPT value normalized to

an effective overburden stress of one atmosphere:

(N1)60 = (N60)/(vo’)0.5 where stress is given in units of

atmospheres.

SPT

Hammer

Calibration

N60 = N (ETR/60)

ETR = EMX / 350 ft-lbs

ENERGY MEASUREMENT

(Corrected N-value)

)(EE

NN60

Field

Field60)100(

PE

EMXETR

nPenetratioRodRod xFWork *

maxt

0

dt)t(V)t(Fdtdt

dx)t(F)t(E)t(W

Donut 45 %

Safety 70-80 %

Automatic 80 – 100 %

(Bowles 1997)

TYPICALLY ASSUMED ETR

CME Automatic (28 hammers):

ETR Average: 80.7%

ETR Range: 75% to 84.5%

Max COV: 10%

HISTORICAL ETR’S

(8 STUDIES 1994 TO 2010)

Hammer operation rate

Rod length

Penetration resistance

Rod type

Secondary impacts

Stress wave dispersion

OTHER VARIABLES AFFECTING ETR

LITERATURE

Year Study Hammer Description Number of

Hammers

Number of

Averages

Overall

Averages ETR

1994

Seattle ASCE

Field Testing

Program

(Batchelor et al.,

1995)

Auto - CME 1 8 - 81.4

Auto - Other 1 5 - 68.5

Auto – Other 1 4 - 72.8

Manual 1 8 - 51.4

Manual 1 8 - 23.1

1997 MnDOT (Lamb,

1997)

Auto - CME 2 - - 80

Auto - Other 1 - - 75

Manual 1 - - 67

1997

Utah State

University

(Butler, 1997)

Auto - CME - - 10 75

Auto - Other - - 5 69

Auto - Other - - 6 49

Manual - - 15 63

Manual - - 3 43

Other - - 3 35

1999

FDOT – U. of

Florida (Davidson

et al., 1997)

Auto- CME 12 101 - 80.1

Auto - Other 2 12 - 76

Manual 43 12 - 66

LITERATURE

Year Study Hammer Description Number of

Hammers

Number of

Averages

Overall

Averages ETR

2001

MDOT – U. of

Maryland

(Aggour and

Radding, 2001)

Auto- CME 1 227 - 81.4

Manual 1 12 - 70.2

Manual 1 12 - 63.5

2005 Caltrans (Liebich,

2005)

Auto- CME 2 8 - 84.5

Auto - Other 2 7 - 82

Manual 6 8 - 54.6

2008

Bechtel

(Biringen and

Davie, 2008)

Auto- CME 28 43 - 81.3

Auto - Other 4 - - 47.9

Auto - Other 1 - - 78.3

Auto - Other 2 - - 79.4

Auto - Other 4 - - 91.8

2010

NCDOT

(Valiquette et al.,

2010)

Auto - (CME & Other) 20 - 20 78.6

Manual 8 - 8 62.3

2010 Vtrans (Kelley

and Lens, 2010)

Auto- CME 6 - 6 82.5

Manual 2 - 2 63.3

Manual 1 - 1 48.1

)(EE

NNField

Field

60

60

CONSEQUENCE OF NOT KNOWING

ETR

Remember

If ETR is higher than 60%, SPT N values will be

too low.

Think about seismic site class, liquefaction,

strength, etc.

The Standard Penetration Test

SPT Energy Correction & Measurement

SPT Energy Calibration of ALDOT Equipment

and Operators

Comparison to Large Scale Calibration Study

Conclusions

OUTLINE

ALDOT TESTING PROGRAM

INSTRUMENTED SUBASSEMBLY

Accelerometers

Strain Gages

SPT ANALYZER

PDAW

2nd round of evaluation of data

PDIPLOT

Organizes data for reporting purposes

PDI Curves

Shows selected F&V traces for reporting purposes

OFFICE ANALYSIS OF FIELD DATA

CALIBRATION CERTIFICATE

Rig I.D.# Single

Records

#

Averages

Overall

Average BPM

STD

(BPM)

COV

(BPM)

Overall

Average ETR

STD

(ETR)

COV

(ETR)

SE9050 220 8 52.65 0.74 1.40 93.1 5.34 5.74

SE9122 396 8 52.05 0.58 1.10 82.2 1.81 2.21

SE9299 355 9 54.83 0.75 1.36 87.7 3.41 3.89

SE9445 281 9 54.14 0.57 1.06 95.2 3.94 4.14

ST11151 214 6 52.13 0.24 0.46 92.2 3.21 3.48

ST11152 228 6 52.95 0.33 0.62 96.1 2.60 2.71

ALDOT RESULTS

Average ETR = 91.1

0

10

20

30

40

50

60

0.0% 20.0% 40.0% 60.0% 80.0% 100.0% 120.0%

Ro

d L

engt

h (f

t)ETR %

SN 9122

SN 9299

SE 9445

ST 11151

ST 11152

SE 9050

EFFECT OF ROD LENGTH

The Standard Penetration Test

SPT Energy Correction & Measurement

SPT Energy Calibration of ALDOT Equipment

and Operators

Comparison to Large Scale Calibration Study

Conclusions

OUTLINE

DATABASE OF SPT TESTS

• SPT energy records

obtained under

NQA-1

• Provided by private

sector consultant

33 Drill rigs

2006 to 2011

17,825 hammer blows of data

485 test depth averages

111 testing events

SUMMARY OF DATABASE

DISTRIBUTION OF ETR (HAMMER

BLOWS)

0

250

500

750

1000

1250

1500

50 55 60 65 70 75 80 85 90 95 100

SP

T H

am

mer

Blo

ws

Energy Transfer Ratio %

ROD TYPE AND LENGTH

0

10

20

30

40

50

60

0 100 200 300 400 500

Nu

mb

er o

f S

PT

Dep

ths

Rod Length Below Gages 10 ft Intervals (ft)

A-Type

N-Type

HAMMER OPERATION RATE

0

500

1000

1500

2000

2500

3000

20 25 30 35 40 45 50 55 60 65 70

SP

T H

am

mer

Blo

ws

CME Hammer Operation Rate (bpm)

OVERALL AVERAGES AND COV

Energy Transfer Ratio

AVE (%)

COV (%)

Sample Size

SPT Hammer Blows 82.9 7.4 17,825

SPT Depths 82.9 6.7 485

SPT Hammer Calibrations

82.9 6.1 111

EFFECT OF ROD SIZE

Rod Group# of

Averages

ETR Average

(%)

ETR STDEV

( %)

ETR COV

(%)

All 485 82.7 5.58 6.75

A-Size 263 82.98 5.84 7.04

N-Size 216 82.63 6.41 7.76

□ # of Hammer Calibrations

▪ COV Ave: 4.5 % ▪

7,911 of the 17,825 hammer blows would have met the criteria of ASTM D4633-10 or the suggested range of hammer operation rates.

Rod length greater than 30ft

SPT N between 10 and 50 bpf

Hammer rate < 60 bpm

ASTM D4633-10 & CME

0

250

500

750

1000

1250

1500

50 55 60 65 70 75 80 85 90 95 100

SP

T H

am

mer

Blo

ws

Energy Transfer Ratio %

CME (Inclusive)

ASTM-CME (Filtered)

Overall average ETR = 84%

COV = 5.7%

ASTM D4633-10 & CME

The Standard Penetration Test

SPT Energy Correction & Measurement

SPT Energy Calibration of ALDOT Equipment

and Operators

Comparison to Large Scale Calibration Study

Conclusions

OUTLINE

SPT is a common geotechnical test.

Despite shortcomings, still the industry standard.

Energy measurement is one way to improve the

quality and reliability of the test.

It is possible to field calibrate the SPT by measuring

energy transferred to the rods by the hammer.

Measure force and velocity, integrate with time to

determine energy transferred.

SUMMARY

ALDOT Hammers Calibrated

Large database of SPT hammer blows collected for

automatic CME hammers

Over 17000 individual hammer blows from 485 SPT

tests in 111 calibration studies

SUMMARY

For ALDOT Hammers:

Energy Range Average – 82.2% - 96.1%

Average for all tested rigs = 91.1%

For CME Automatic Hammers:

Overall Average – 82.9% ETR

Expected Variation – COV 7.4%

CONCLUSIONS

ALDOT

Auburn Highway Research Center

Jonathan N. Honeycutt, M.S.

GRL Engineers, Inc.

Steve E. Kiser, M.E., P.E.

AMEC, Inc.

ACKNOWLEDGEMENTS

J. Brian

Anderson,

Associate

Professor of

Civil

Engineering

Auburn

University

Database

Evaluation of

Energy Transfer

for CME

Automatic

Hammer Standard

Penetration Tests

October 28, 2014

45th Annual Southeastern

Transportation

Geotechnical Engineering

Conference

Mobile, AL