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

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

Site MapSite Air Photo Emeryville, N. California

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

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

900-ft Soil Profile

CU Triaxial Testing

Emeryville Soil Profile *=Friction angle and Cohesion parameters were increased 25 & 50% in parametric analysis Fill: (pre-drilled) Soft - Silty Clay Firm Sandy Clay Stiff Sandy Clay V. Stiff Sandy Clay 10’ 35’ 10’ 18’ NA /24.5/28.6* 400/500/600* /27.9/32.5* 600/750/900* /32.5/37.4* 1000/1250/1500* 0.75 No. 16” Square Pile Soil Type  (pcf)  (deg) C (psf) Ca/C ’

PILE LENGTH (ft) PILE DRIVING (BLOWS PER FOOT ) IP7 IP8 IP9 IP10 IP5 IP11 IP12 IP13 Pile Driving Blow Counts & N-Values

ASTM D 1143 Static 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

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

RLT Procedure 25,000 kg mass dropped on pile from varying heights Deflection 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

FUNDEX-PLT BLACK BOX TEST SETUP RLT Equipment

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

RLT Load Application

Rate of Loading Ladd 1974 & Graham 1983 S u /(S u for  =1%/hr)= *Log s Where: S u = Undrained shear strength s= Strain The resulting loading rate for the RLT is: 3.6X10 6 Percent/Hour. Therefore SI for Cohesive soils is 1.7

Davisson Method - Pile Capacities Plot Load versus Deflection Plot pile elastic shortening line Compute offsett  = (B/12) Plot line parallel to elastic shortening line Compute pile capacity form curve

Theoretical Pile Capacities NAVFAC 7.2 Input parameters: –K hc =1.5 K ht =0.75  =0.75 –E p,=4.415E6-psiC p,=0.03  s =0.33 Total Elongation:  t =  p +  fric. Total Settlement:  t =  p +  fric. +  tip

Uplift Test Analysis & Results

Summary of Results

RLT & Theory

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

FLAC – Cohesion Block Values y x Cohesion in PSF

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

FLAC – RLT Simulation SI=1.0 y x Load (Pounds) Deformation (Ft) 800,000 lbs 700,000 lbs Cohesion parameter same as Triaxial Test Results

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

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

RLT & FLAC

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

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”

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

Richmond BART and UCSF Mission Bay

BART RLT

UCSF - Test 19A #5 - Davisson

UCSF - Test 19A #3 - Davisson

UCSF - Test 19A #5 - Davisson

UCSF - Test 19A #5 – Chin-Konders - 1

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

UCSF - Test 19A #5 – Hansen - 1

UCSF - Test 19A #5 – Hansen 2

UCSF - Test 19A #3 – De Beers

N4 West

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