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CAPWAP AND REFINED WAVE EQUATION ANALYSES FOR DRIVEABILITY PREDICTIONS AND CAPACITY ASSESSMENT OF OFFSHORE PILE INS

CAPWAP AND REFINED WAVE EQUATION ANALYSES FOR DRIVEABILITY PREDICTIONS AND CAPACITY ASSESSMENT OF OFFSHORE PILE INSTALLATIONS. OMAE 2009 Honolulu, HI - May 31 to June 5 2009. Frank Rausche, M att Nagy, Scott Webster GRL Engineers, Inc. Liqun Liang Pile Dynamics, Inc. Outline.

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CAPWAP AND REFINED WAVE EQUATION ANALYSES FOR DRIVEABILITY PREDICTIONS AND CAPACITY ASSESSMENT OF OFFSHORE PILE INS

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  1. CAPWAP AND REFINED WAVE EQUATION ANALYSESFOR DRIVEABILITY PREDICTIONS ANDCAPACITY ASSESSMENT OF OFFSHORE PILE INSTALLATIONS OMAE 2009 Honolulu, HI - May 31 to June 5 2009 Frank Rausche, Matt Nagy, Scott Webster GRL Engineers, Inc.Liqun Liang Pile Dynamics, Inc.

  2. Outline • Background • PDA Testing and CAPWAP • Bearing Graph and Driveability • Variable Soil Setup and Plugging Effects • Problem Statement • Procedures and Examples for • Blow Count Depth Matching (BCDM) • Refined Wave Equation Analysis (REWE) • Summary Rausche Nagy Webster Liang: CAPWAP and Refined Wave Equation Analyses …..

  3. Dynamic pile testing and analysis • Using Pile Driving Analyzer® measure pile top velocity during pile installation; monitoring results include • Stresses • Integrity • Hammer performance • Capacity estimate • Perform signal matching with CAPWAP® to calculate capacity plus resistance distribution Rausche Nagy Webster Liang: CAPWAP and Refined Wave Equation Analyses …..

  4. CAPWAP (Signal Matching) Result Rausche Nagy Webster Liang: CAPWAP and Refined Wave Equation Analyses …..

  5. Wave equation analysis • Based on Smith’s concept • Input requirement • Hammer properties • Driving system details • Pile geometry • Soil information • GRLWEAP analysis options include • Bearing Graph • Driveability GRLWEAP Bearing Graph Rausche Nagy Webster Liang: CAPWAP and Refined Wave Equation Analyses …..

  6. Wave equation analysis GRLWEAP Driveability Output: Assumption: soil setup gain on shaft is function of log (time) Rausche Nagy Webster Liang: CAPWAP and Refined Wave Equation Analyses …..

  7. Problem Statement • We may do PDA/CAPWAP for one pile but need capacity assessment for others  Do Refined wave equation analysis (REWE) • We may have a driving record but no measurements and have to assess bearing capacity  Do Blow Count-Depth Matching (BCDM) Rausche Nagy Webster Liang: CAPWAP and Refined Wave Equation Analyses …..

  8. The REWE Procedure Rausche Nagy Webster Liang: CAPWAP and Refined Wave Equation Analyses …..

  9. REWE Example – Pile Details • 1067 mm dia. OE pipe – 100 m long • 3 pile sections • Wall thickness: 34 – 44 mm • Final penetration: 42 m • Final blow count: 17 bl / 0.25 m Rausche Nagy Webster Liang: CAPWAP and Refined Wave Equation Analyses …..

  10. REWE Example – Soil Details • Alternate layers of • Carbonate clays; Shear strength 100 to 450 kPa • Silty, calcareous sands; med. dense to dense • Soils increasing in strength with depth Rausche Nagy Webster Liang: CAPWAP and Refined Wave Equation Analyses …..

  11. REWE Example - Hammer • Menck MHU 500T • 294 kN ram weight • 550 kJ maximum rated energy (1.87 m equiv. stroke) • 500 kJ max. applied energy (1.70 m equiv. stroke) Rausche Nagy Webster Liang: CAPWAP and Refined Wave Equation Analyses …..

  12. Measurements PDA Measurements 3.5 m below top of pile with 2 strain transducers and 2 PR accelerometers Rausche Nagy Webster Liang: CAPWAP and Refined Wave Equation Analyses …..

  13. REWE ExamplePDA - EOD Results Rausche Nagy Webster Liang: CAPWAP and Refined Wave Equation Analyses …..

  14. REWE Example – EOD CAPWAP Results Rausche Nagy Webster Liang: CAPWAP and Refined Wave Equation Analyses …..

  15. CAPWAP Analysis • Force and Velocity Measurements plus pile impedance • Calculated Load-Set Curve Rausche Nagy Webster Liang: CAPWAP and Refined Wave Equation Analyses …..

  16. Wave Equation Model • GRLWEAP Hammer Model • Driving System as per contractor • Pile Model with stabbing guides • Soil model from CAPWAP Rausche Nagy Webster Liang: CAPWAP and Refined Wave Equation Analyses …..

  17. CAPWAP and GRLWEAP Input/Output Values Rausche Nagy Webster Liang: CAPWAP and Refined Wave Equation Analyses …..

  18. CAPWAP and GRLWEAP Input/Output Values Rausche Nagy Webster Liang: CAPWAP and Refined Wave Equation Analyses …..

  19. Comparison of measured with GRLWEAP calculated force and velocity Rausche Nagy Webster Liang: CAPWAP and Refined Wave Equation Analyses …..

  20. Second Procedure: BCDM Rausche Nagy Webster Liang: CAPWAP and Refined Wave Equation Analyses …..

  21. BCDM – Example properties as before • 1st Step: Obtain driving log • Blow count vs depth • Hammers and Energy settings • Driving interruption durations • Maybe average of several pile driving logs Rausche Nagy Webster Liang: CAPWAP and Refined Wave Equation Analyses …..

  22. BCDM Get fsvs depth from geotechnical report (starting value) Rausche Nagy Webster Liang: CAPWAP and Refined Wave Equation Analyses …..

  23. BCDM • Get qtvs depth from geotechnical report (starting value) • Determine from driving log match • Modified fs • Setup factor • Modified qt • Effective toe area Rausche Nagy Webster Liang: CAPWAP and Refined Wave Equation Analyses …..

  24. BCDM – Blow Count match • Predict long term capacity from • modified fs, • modified qt, • setup factor • effective toe area Rausche Nagy Webster Liang: CAPWAP and Refined Wave Equation Analyses …..

  25. Summary • The bearing capacity of offshore piles can be assessed by the following methods: • From measurements at EOD and CAPWAP capacity at EOD  Capacity at EOD • From monitored restrikes plus CAPWAP capacity including partial setup  Capacity at BOR – may be extrapolated to later times • For similar non-monitored piles using REWE • From driving record by BCDM  Extrapolated, estimated capacity from driving interruption information Rausche Nagy Webster Liang: CAPWAP and Refined Wave Equation Analyses …..

  26. Summary (continued) • REWE, the REfined Wave Equation analysis requires measurements and helps determine capacity for non-monitored piles driven in similar soils. • REWE requires matching of • Transferred energy and top stress from PDA • Blow count and CAPWAP capacity Rausche Nagy Webster Liang: CAPWAP and Refined Wave Equation Analyses …..

  27. Summary (continued) • BCDM, the blow count-depth matching procedure determines bearing capacity from driving behavior • Generally applied to the complete driving log, including energy and driving interruptions • Driving interruption or restrike information allows for soil setup assessment • Without measurements results depend on hammer performance assumptions Rausche Nagy Webster Liang: CAPWAP and Refined Wave Equation Analyses …..

  28. Thank You, OMAE Conference Rausche, Nagy, Webster, Liang CAPWAP AND REFINED WAVE EQUATION ANALYSES FOR DRIVEABILITY PREDICTIONS AND CAPACITY ASSESSMENT OF OFFSHORE PILE INSTALLATIONS

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