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Yogesh Prashar, P.E., GE Force Pulse Conference, DFI January 2012 Oakley, California

Classical and Finite Difference Method to Estimate pile Capacity Compared With Pile Load Test Results. Yogesh Prashar, P.E., GE Force Pulse Conference, DFI January 2012 Oakley, California. www.m2consultantsinc.com. Presentation Outline. Description & Background

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Yogesh Prashar, P.E., GE Force Pulse Conference, DFI January 2012 Oakley, California

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  1. Classical and Finite Difference Method to Estimate pile Capacity Compared With Pile Load Test Results Yogesh Prashar, P.E., GE Force Pulse Conference, DFI January 2012 Oakley, California www.m2consultantsinc.com

  2. Presentation Outline • Description & Background • Pile Load Testing & Results ETC • 3 Conventional Uplift Tests • 12 RLT Compression • Theoretical Load Settlement Calculations • FLAC Simulation of Uplift & RLT • Comparisons & Rapid Loading • BART, UCSF, & N4 West • Conclusions

  3. Emeryville, N. California Site Map Site Air Photo

  4. 15-test Pile Locations 3 Uplift - Pile Load Test 400’ 12 RLT 900’ RLT Conventional Uplift Test 16-in Square pre-cast concrete piles

  5. Site Plan & X-Section Line A’ TEST AREA N Site Plan & Boring Locations Cross Section Line A-A’ & B-B’ 12 Borings & 7 CPT’s Laboratory Testing

  6. Soil Profile 900-ft

  7. CU Triaxial Testing

  8. Emeryville Soil Profile No. 16” Square Pile Soil Type g (pcf)f(deg)C (psf) Ca/C 115 20 0 NA 110 5 200 0.9 125 20/24.5/28.6* 400/500/600* 0.9 130 24/27.9/32.5* 600/750/900* 0.8 130 27/32.5/37.4* 1000/1250/1500* 0.75 Fill: (pre-drilled) Soft - Silty Clay Firm Sandy Clay Stiff Sandy Clay V. Stiff Sandy Clay 10’ 35’ 10’ 18’ 1 2 3 4 5 86’ *=Friction angle and Cohesion parameters were increased 25 & 50% in parametric analysis

  9. B-13 B-12 SPT N-VALUE (BLOWS PER FOOT) 0.0 10.0 20.0 30.0 40.0 50.0 60.0 10.0 B-11 B-10 0.0 B-9 -10.0 B-8 -20.0 B-7 B-6 ELEVATION (FT) -30.0 B-5 -40.0 B-4 B-3 -50.0 B-2 -60.0 B-1 -70.0 -80.0 Pile Driving Blow Counts & N-Values PILE DRIVING (BLOWS PER FOOT ) 0.0 4.0 8.0 12.0 2.0 6.0 10.0 14.0 25.0 IP13 35.0 IP12 45.0 IP11 PILE LENGTH (ft) IP5 55.0 IP10 65.0 IP9 75.0 IP8 85.0 IP7 95.0

  10. ASTM D 1143Static Pile Load Test • Three piles were tested • Load applied with hydraulic jacks • Deflection by Dial indicators • Plotted Measured Load versus deflection • Material Parameters were back calculated to fit Conventional load deflection curves • Parameters fit within a range of field and lab tests results

  11. ASTM D 1143 Load Cell (Load) Reinforcing Bars Test Frame Wooden Planks Wooden Planks Test Pile Dial Indicators (deformation) Ca Subsurface Soils

  12. RLT Procedure • 25,000 kg mass dropped on pile from varying heights • Deflection Measured @ Point of Impact • Force applied to pile top for 200-ms duration • Energy transmitted to pile via anvil and dampened via springs • Springs recoil and push load up to unload pile

  13. RLT Equipment TEST SETUP FUNDEX-PLT BLACK BOX

  14. Hydraulic Clamp 25,000 kg mass Anvil Damping Springs Black Box Data Rec. TestPile Subsurface Soils RLT Procedure

  15. RLT Load Application

  16. Rate of LoadingLadd 1974 & Graham 1983 • Su/(Su for e =1%/hr)=1.0+0.1*Log s • Where: • Su = Undrained shear strength • s= Strain • The resulting loading rate for the RLT is: 3.6X106 Percent/Hour. • Therefore SI for Cohesive soils is 1.7

  17. Davisson Method - Pile Capacities • Plot Load versus Deflection • Plot pile elastic shortening line • Compute offsett d=0.15+0.1(B/12) • Plot line parallel to elastic shortening line • Compute pile capacity form curve

  18. Theoretical Pile Capacities • NAVFAC 7.2 • Input parameters: • Khc=1.5 Kht=0.75 d=0.75 • Ep,=4.415E6-psi Cp,=0.03 as=0.33 • Total Elongation: dt = dp + dfric. • Total Settlement: dt = dp + dfric. + dtip

  19. Uplift Test Analysis & Results

  20. Summary of Results

  21. RLT & Theory

  22. Numerical Modeling - FLAC • FLAC – 2D Finite Difference Model • Cohesion parameter from CU Triaxial • Mohr Coulomb Model • Pile Element to model 16-inch square pile • Soil pile interaction parameters calibrated to uplift Test then soil pile stiffness parameters were increased by a factor of 2 for RLT simulations • Sinusoidal Loading function applied at pile head to simulate RLT

  23. FLAC – Cohesion Block Values Cohesion in PSF y x

  24. FLAC - Y-Displacement Contours Apply tension load till equilibrium Contours in Feet y x

  25. FLAC – RLT Simulation SI=1.0 2.2-inches @ 700,000 lbs Deformation (Ft) Cohesion parameter same as Triaxial Test Results 4.2-inches @ 800,000 lbs y Load (Pounds) x

  26. FLAC – RLT Simulation SI=1.5 Deformation (Ft) Cohesion parameter 1.5 times Triaxial Test Results 1.4-inches @ 800,000 lbs y Load (Pounds) x

  27. FLAC – RLT Simulation SI=2.0 Deformation (Ft) Cohesion parameter 2.0 times Triaxial Test Results 1.0-inches @ 800,000 lbs y Load (Pounds) x

  28. RLT & FLAC

  29. CONCLUSIONS • Classical theoretical values deviate from observed data at higher loads • RLT capacity results were about 2.0 X higher than the theoretical values • A 1.7 X Strength Increase correlates well with published data • Dynamic nature of the RLT mimic seismic conditions

  30. CONCLUSIONS (CONT.) • Designer could test several piles per day with RLT in cohesive material calibrate material parameters to match the observed data and then apply strength reduction to “Calibrated” parameters and establish “Ultimate Pile Capacities” • Lower Factor of Safety could be applied to the “Allowable Pile Capacity”

  31. CONCLUSIONS Classical theoretical values deviate from observed data at higher loads RLT capacity results were about 2.0 X higher than the theoretical values A 1.7 X Strength Increase correlates well with published data Dynamic nature of the RLT mimic seismic conditions

  32. Richmond BART and UCSF Mission Bay

  33. BART RLT

  34. BART RLT

  35. UCSF - Test 19A #5 - Davisson

  36. UCSF - Test 19A #3 - Davisson

  37. UCSF - Test 19A #5 - Davisson

  38. UCSF - Test 19A #5 – Chin-Konders - 1

  39. UCSF - Test 19A #5 Chin-Konders-2

  40. UCSF - Test 19A #5 – Hansen - 1

  41. UCSF - Test 19A #5 – Hansen 2

  42. UCSF - Test 19A #3 – De Beers

  43. N4 West

  44. Classical and Finite Difference Method to Estimate pile Capacity Compared With Pile Load Test Results Yogesh Prashar, P.E., GE Force Pulse Conference, DFI January 2012 Oakley, California www.m2consultantsinc.com

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