SPT TestingSPT Testing

ProblemsProblems

(Trials and Tribulations)(Trials and Tribulations)

George GobleGeorge Goble

The BeginningThe Beginning• Schmertmann and Palaccio Schmertmann and Palaccio (Spelling)(Spelling)

• He Wanted EnergyHe Wanted Energy– E = E = ƒF(t)v(t)dtƒF(t)v(t)dt– Measure Force and Acceleration and Measure Force and Acceleration and

Integrate the AccelerationIntegrate the Acceleration• Obviously SimpleObviously Simple

• Measurement Difficulties on a(t)Measurement Difficulties on a(t)– But, v=(c/EA)FBut, v=(c/EA)F

• Up to 2L/c, Then CorrectionUp to 2L/c, Then Correction

– Therefore, E=(c/EA)Therefore, E=(c/EA)ƒFƒF22(t)dt(t)dt– What is the ProblemWhat is the Problem

NN60 60 ==NNmm * E * Emm

Wh (60%)Wh (60%)

If based on the safety hammer, then evidence suggests If based on the safety hammer, then evidence suggests standardizing on a slightly higher energy ratio. standardizing on a slightly higher energy ratio. If based on donut hammer, then very limited evidence If based on donut hammer, then very limited evidence suggests standardizing on an even lower energy ratio.suggests standardizing on an even lower energy ratio.

NN6060

SPTSPTTESTTEST

SETUPSETUP

SPTSPTTIPTIP

HAUGE HAUGE TESTTEST19771977

WithWith60 kHz60 kHz

FrequencyFrequency

ContentContent

Hammer Type

EFV avg

C.O.V

Samples

Cathead-rope 63 12 15

CME automatic 75 9 10

Spooling winch 35 8 3

Hydraulic auto 69 15 5

Donut 43 22 3

Other Auto 49 13 6

Data from GRL compiled by Dr. Joe CaliendoData from GRL compiled by Dr. Joe Caliendo

Utah State Utah State SPT Energy StudySPT Energy Study

Utah State Utah State SPT Energy StudySPT Energy Study

HammerType

EFVavg

Std Devof EFV

Std DevEach test

Numberof Tests

Numberof SPT

SafetyRope/cathead

66.0 10.7 4.1 227 43

Automatic 79.6 7.9 2.3 113 14

Florida DOT Florida DOT SPT Energy StudySPT Energy Study

Florida DOT Florida DOT SPT Energy StudySPT Energy Study

• ““Standard Penetration Test Energy Calibrations” Standard Penetration Test Energy Calibrations” performed by University of Florida, Gainesvilleperformed by University of Florida, Gainesville– by Dr. John Davidson, J. Maultsby and Kimberly Spoorby Dr. John Davidson, J. Maultsby and Kimberly Spoor– report issued January 31, 1999report issued January 31, 1999

• ““Standard Penetration Test Energy Calibrations” Standard Penetration Test Energy Calibrations” performed by University of Florida, Gainesvilleperformed by University of Florida, Gainesville– by Dr. John Davidson, J. Maultsby and Kimberly Spoorby Dr. John Davidson, J. Maultsby and Kimberly Spoor– report issued January 31, 1999report issued January 31, 1999

Comparison of StudiesComparison of StudiesComparison of StudiesComparison of Studies

Hammer Study EFV avg C.O.V.

Safety Utah State 63 12

Florida DOT 66 11

Automatic Utah State 75 9

Florida DOT 80 8

INFLUENCE OF ROD AREA INFLUENCE OF ROD AREA ON SPT N-VALUEON SPT N-VALUE

George GobleGeorge Goble

Goble EngineeringGoble Engineering

SPT WAVE EQUATIONSPT WAVE EQUATIONANALYSISANALYSIS

• SPT Driving System and Rod Can be SPT Driving System and Rod Can be Modeled on Wave EquationModeled on Wave Equation– Used Ram of CME Auto SystemUsed Ram of CME Auto System

• N-Values Were Determined for up to N-Values Were Determined for up to 200 feet of Rod with 10 to 30 Starting N-200 feet of Rod with 10 to 30 Starting N-ValuesValues

• Mechanical Part of System Can Be Mechanical Part of System Can Be Modeled with Accuracy and Reliability Modeled with Accuracy and Reliability

TOP FORCE-100 FT RODTOP FORCE-100 FT ROD

-2

0

2

4

6

8

10

12

14

16

18

20

0 20 40 60 80 100 120 140 160

Time (ms)

Forc

e (k

ips)

TOP VELOCITY-100 FT RODTOP VELOCITY-100 FT ROD

-4

-2

0

2

4

6

8

10

12

14

16

18

0 20 40 60 80 100 120 140 160

Time (ms)

Velo

city

(ft/s

ec)

TOP DISPLACEMENT- 100FT RODTOP DISPLACEMENT- 100FT ROD

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

0 20 40 60 80 100 120 140 160

Time (ms)

Dis

plac

emen

t (in

)

N=10N=10

0

2

4

6

8

10

12

14

0 50 100 150 200 250

Rod Length (ft.)

N-V

alu

eA

N

N=15N=15

0

2

4

6

8

10

12

14

16

18

20

0 50 100 150 200 250

Rod Length (ft.)

N -

Va

lue

NA

N=20N=20

0

5

10

15

20

25

30

0 50 100 150 200 250

Rod Length (ft.)

N -

Va

lue

N

A

N=25N=25

0

5

10

15

20

25

30

35

40

0 50 100 150 200 250

Rod Length (ft.)

N -

Va

lue

N

A

N=30N=30

0

5

10

15

20

25

30

35

40

45

50

0 50 100 150 200 250

Rod Length (ft.)

N -

Va

lue

N

A

N ROD WITH INSERTS

A ROD W.O. INSERTS

CPT NBRAUN UNCORRECTED N

N

DE

PT

HCOMPARISONOF N-VALUES

FORA AND

N RODS

FROMMINNESOTA

DOT

COMMENTSCOMMENTS

• Energy Measurement now RoutineEnergy Measurement now Routine– Standards Should Allow Different Strokes Standards Should Allow Different Strokes

to Get Required Impact Velocityto Get Required Impact Velocity• Impact Velocity Could Be Measured by RigImpact Velocity Could Be Measured by Rig• Then Correction Not RequiredThen Correction Not Required

• Rod Area Should Be StandardizedRod Area Should Be Standardized– Probably to about 1 Sq. In.Probably to about 1 Sq. In.

• Driving System Should Be StandardizedDriving System Should Be Standardized

““Standard” Penetration TestingStandard” Penetration Testing“Non-standard” variables“Non-standard” variables

““Standard” Penetration TestingStandard” Penetration Testing“Non-standard” variables“Non-standard” variables

• HammersHammers– SafetySafety– AutomaticAutomatic– DonutDonut

• OperatorsOperators– ManualManual– Semi-automaticSemi-automatic– AutomaticAutomatic

• Drill RodsDrill Rods– SizeSize– LengthLength

• Lift MechanismsLift Mechanisms– Cathead-ropeCathead-rope– Cathead diameterCathead diameter– Spooling WinchSpooling Winch

• Drill MethodsDrill Methods– Hollow Stem AugersHollow Stem Augers– Drilling FluidsDrilling Fluids

• Split Tube SamplerSplit Tube Sampler– ShapeShape– Liners or notLiners or not

THE ENDTHE END