SPT Testing Problems (Trials and Tribulations) George Goble

The Beginning Schmertmann and Palaccio (Spelling)Schmertmann and Palaccio (Spelling) He Wanted EnergyHe Wanted Energy –E = ƒF(t)v(t)dt –Measure Force and Acceleration and Integrate the Acceleration Obviously SimpleObviously Simple Measurement Difficulties on a(t)Measurement Difficulties on a(t) –But, v=(c/EA)F Up to 2L/c, Then CorrectionUp to 2L/c, Then Correction –Therefore, E=(c/EA)ƒF 2 (t)dt –What is the Problem

EFV 65% EF2 64% ExampleExample

N 60 = N m * E m Wh (60%) If based on the safety hammer, then evidence suggests standardizing on a slightly higher energy ratio. If based on donut hammer, then very limited evidence suggests standardizing on an even lower energy ratio. N 60

SPT TEST SETUP

SPT TIP

HAUGE TEST 1977 With 60 kHz Frequency Content

Data from GRL compiled by Dr. Joe Caliendo Utah State SPT Energy Study

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

Comparison of Studies HammerStudyEFV avg C.O.V. SafetyUtah State 6312 Florida DOT 6611 AutomaticUtah State 759 Florida DOT 808

INFLUENCE OF ROD AREA ON SPT N-VALUE George Goble Goble Engineering

SPT WAVE EQUATION ANALYSIS SPT Driving System and Rod Can be Modeled on Wave EquationSPT Driving System and Rod Can be Modeled on Wave Equation –Used Ram of CME Auto System N-Values Were Determined for up to 200 feet of Rod with 10 to 30 Starting N- ValuesN-Values Were Determined for up to 200 feet of Rod with 10 to 30 Starting N- Values Mechanical Part of System Can Be Modeled with Accuracy and ReliabilityMechanical Part of System Can Be Modeled with Accuracy and Reliability

TOP FORCE-100 FT ROD

TOP VELOCITY-100 FT ROD

TOP DISPLACEMENT- 100FT ROD

N=10 A N

N=15 N A

N=20 N A

N=25 N A

N=30 N A

N ROD WITH INSERTS A ROD W.O. INSERTS CPT N BRAUN UNCORRECTED N N DEPTH COMPARISON OF N-VALUES FOR A AND N RODS FROM MINNESOTA DOT

COMMENTS Energy Measurement now RoutineEnergy Measurement now Routine –Standards Should Allow Different Strokes to 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. Driving System Should Be StandardizedDriving System Should Be Standardized

“Standard” Penetration Testing “Non-standard” variables HammersHammers –Safety –Automatic –Donut OperatorsOperators –Manual –Semi-automatic –Automatic Drill RodsDrill Rods –Size –Length Lift MechanismsLift Mechanisms –Cathead-rope –Cathead diameter –Spooling Winch Drill MethodsDrill Methods –Hollow Stem Augers –Drilling Fluids Split Tube SamplerSplit Tube Sampler –Shape –Liners or not

THE END