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SPT Testing Problems (Trials and Tribulations) George Goble

SPT Testing Problems (Trials and Tribulations) George Goble. The Beginning. Schmertmann and Palaccio (Spelling) He Wanted Energy E = ƒF(t)v(t)dt Measure Force and Acceleration and Integrate the Acceleration Obviously Simple Measurement Difficulties on a(t) But, v=(c/EA)F

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SPT Testing Problems (Trials and Tribulations) George Goble

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  1. SPT TestingProblems(Trials and Tribulations)George Goble

  2. The Beginning • Schmertmann and Palaccio (Spelling) • He Wanted Energy • E = ƒF(t)v(t)dt • Measure Force and Acceleration and Integrate the Acceleration • Obviously Simple • Measurement Difficulties on a(t) • But, v=(c/EA)F • Up to 2L/c, Then Correction • Therefore, E=(c/EA)ƒF2(t)dt • What is the Problem

  3. Nm * Em N60 = Wh (60%) N60 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.

  4. SPTTESTSETUP

  5. SPTTIP

  6. HAUGE TEST1977With60 kHzFrequencyContent

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

  8. Florida DOT SPT Energy Study • “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

  9. Comparison of Studies Hammer Study EFV C.O.V. avg Safety Utah State 63 12 Florida DOT 66 11 Automatic Utah State 75 9 Florida DOT 80 8

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

  11. SPT WAVE EQUATIONANALYSIS • SPT 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-Values • Mechanical Part of System Can Be Modeled with Accuracy and Reliability

  12. TOP FORCE-100 FT ROD

  13. TOP VELOCITY-100 FT ROD

  14. TOP DISPLACEMENT- 100FT ROD

  15. N=10 A N

  16. N=15 N A

  17. N=20 N A

  18. N=25 N A

  19. N=30 N A

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

  21. COMMENTS • Energy Measurement now Routine • Standards Should Allow Different Strokes to Get Required Impact Velocity • Impact Velocity Could Be Measured by Rig • Then Correction Not Required • Rod Area Should Be Standardized • Probably to about 1 Sq. In. • Driving System Should Be Standardized

  22. “Standard” Penetration Testing“Non-standard” variables • Lift Mechanisms • Cathead-rope • Cathead diameter • Spooling Winch • Drill Methods • Hollow Stem Augers • Drilling Fluids • Split Tube Sampler • Shape • Liners or not • Hammers • Safety • Automatic • Donut • Operators • Manual • Semi-automatic • Automatic • Drill Rods • Size • Length

  23. THE END

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