3. www.fugro.comwww.loadtest.com
Which Deep Foundation Type?
• Type of Load
(axial, lateral, torsion)
• Magnitude of Load
• Project Size & Complexity
• Site Conditions
• Environmental Conditions
• Local Availability & Price
• Familiarity (engineer, client) & complacency
• Foundation Cost Controlled by Uncertainty
(conservative design plus safety factor)
Engineering
Decisions
4. www.fugro.comwww.loadtest.com
Deep Foundation Design Uncertainty
• Site Variability
• Axial, lateral, depth to bearing stratum
• Strength, stiffness, test quality
• Typically test < 0.01% of site
• Design Method: RN = Rside + Rbase
• Calibration, empiricism, codes, resistance or
safety factors based on uncertainty
• Construction Quality
• Contractor experience
• Quality of supervision
5. www.fugro.comwww.loadtest.com
Reduce Cost by Reducing Uncertainty:
• Informed design (integrated investigation:
geophysics + insitu testing + sampling)
• Design verification (static & dynamic testing)
• Optimization (redesign)
• reduce length, size, number
• change type (driven, drilled, anchor)
• reduce cost and construction time ($$)
• FLT’s experience - savings 5X test cost
• Quality control testing to assure performance
& reduce remediation cost
6. www.fugro.comwww.loadtest.com
Integrated Ground Investigation
• Measure ground properties for design
• More time characterizing site → more reliable design
• Staged approach - progressively more targeted
• Geophysical techniques provide overview
• Insitu testing (CPT/DMT) calibrates geophysics, reduces
sampling disturbance and laboratory testing uncertainty
• Insitu profiling (CPT) identifies thin layers missed by
drilling and sampling program
• SPT not so great (drilling disturbance, variable energy)
• Sampling and testing to characterize problem zones
• Does not have to cost more, and can cost less
• Preliminary pile tests included to prepare better plans?
7. www.fugro.comwww.loadtest.com
Horizontal Distance, m
Depth,m
Sand
Silty Clay
Clayey
Sand
Sounding
Stopped
at 33.5 m
Silty Clay
Clayey
Sand
0 2010
CPT 03 qc, MPa
0
5
10
15
20
Sand
Clay
Silty
Clay
Sand
Clayey
Sand
Refusal
0 2010
CPT 01 qc, MPa
Depth,m
Time,ns
CPT 01
CPT 03
GPR
Example
UF
Insitu
Test
Site
20. www.fugro.comwww.loadtest.com
Bi-Directional Osterberg Cell Testing
• Specialized jack in pile uses
bearing to mobilize side shear
• Developed by
Dr. Jorj Osterberg and AEFC
• LOADTEST Inc. founded 1991
(purchased by Fugro in 2008)
• First “O-cell” tests on driven
steel pipe piles 1987
• >2000 O-cell tests to date,
mostly drilled shafts (300+/yr)
• ~ 30 driven piles since 1987
(12”-66”, 52 tons – 1,480 tons)
22. www.fugro.comwww.loadtest.com
O-cell Features
• Robust for installation
• Aligned with pile axis
• Special seal for eccentricity
• Water used for hydraulic fluid
• Rated at 10,000 psi
• Calibrated by AEFC
(NIST Traceability)
• Linear & Repeatable
• Strain gauges
also confirm load
24” PHC Korea
23. www.fugro.comwww.loadtest.com
O-cell Instrumentation
• O-cell Pressure monitored
by gauge and transducer
• Pile Top Movement
• O-cell Expansion
Transducers
• O-cell Top Telltales
• Pile Bottom Telltales
• Embedded Strain Gauges
• Embedded Pile
Compression Transducers
25. www.fugro.comwww.loadtest.com
Typ. O-cell Test – No Reference Beams
Leica digital levels monitor targets on top of shaft directly.
Accuracy actually improved (Sinnreich, Simpson, DFI Journal, 2009).
26. www.fugro.comwww.loadtest.com
Driven Pile O-cell Test Setup
• ASTM D1143
Quick Test (new
standard coming)
• 20 Loads to failure
• 8 min load intervals
(identify creep limit)
• All instruments
monitored by
datalogger
• Real-time load
vs. deflection plot
• Reference beams
replaced by
electronic levels
27. www.fugro.comwww.loadtest.com
Load Transfer from O-cell & Strain Gauges
+465
+475
+485
+495
+505
+515
+525
+535
+545
+555
+565
+575
0 500 1,000 1,500 2,000 2,500
Elevation(ft)
O-cell Load ( kips )
Top of Shaft
Bottom of Shaft
1L-1 1L-3 1L-5 1L-7 1L-9
S. G. Level 6
S. G. Level 5
S. G. Level 2
S. G. Level 3
O-cell Load
1L-11 1L-13 1L-171L-15 1L-19
28. www.fugro.comwww.loadtest.com
Side Shear from Load Transfer
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
0.0 0.5 1.0 1.5 2.0 2.5
MobilizedNetUnitSideShear(ksf)
Upward Average Shear Zone Displacement ( in )
S.G. Level 6 to Zero Shear
S.G. Level 5 to S.G. Level 6
S.G. Level 3 to S.G. Level 5
S.G. Level 2 to S.G. Level 3
O-cell to S.G. Level 2
40. www.fugro.comwww.loadtest.com
O-cells in Driven Piles
O-cell cast into or welded
to pile before driving
O-cell grouted into pile
after driving
66” Cylinder Pile, Harrison County, MS30” PSC Pile, Morgan City, LA
41. www.fugro.comwww.loadtest.com
Example: 18” Steel Pipe Piles, MA
Saugus River Bridge Pines River Bridge
• Delmag
D62-22
• Refusal
10 blows
per 0.5”
• 142 tons
O-cell Load
• 0.28 tsf Side
Resistance
Failure
(0.3”)
• 80 tsf
End Bearing
(not failed)
• 284 tons
Capacity
• Delmag
D36-13
• Refusal
10 blows
per 0.5”
• 215 tons
O-cell Load
• 0.39 tsf Side
Resistance
Failure
(0.3”)
• 122 tsf
End Bearing
(not failed)
• 430 tons
Capacity
42. www.fugro.comwww.loadtest.com
FL Research Pile Setup
• Five 18” PSC Piles
• PDA Tests
• Long-term, staged
static tests (25)
• Osterberg Cell in tip
• Strain Gages
• Telltales
• Piezometers
• DMT Stress Cells Osterberg Cell
Cast Into Pile,
with XXS Pressure Pipe
to Top
Pile
Side
Shear
Pile End Bearing
O-cell® Top
Telltales Inside PVC
Pipe
O-cell® Bottom Telltale (through center of
pressure pipe)
Friction Collar
for Gage Support
O-cell®
Tee
(not to scale)
Dilatometer Cell (L)
& VW Piezometer (R)
on Pile Face
VW Strain Gage
(in pairs, tied to prestress
strands)
Hydraulic Pump
with Gage
& Piezometer
Wireline & Scale
44. www.fugro.comwww.loadtest.com
0 50 100 150 200 250 300
0
500
1000
1500
2000
2500
Aucilla, Static Test
Aucilla, Dynamic Test
1 min
15 min
60 min
1727 days
Elapsed Time, t (days)
PileSideShearQS(kN)
Bullock et al. (1995) in FL
18” PSC, O-cell at bottom
FL Research Pile Setup – Arithmetic Plot
= 225 tons
45. www.fugro.comwww.loadtest.com
0.001 0.01 0.1 1 10 100 1000
0
500
1000
1500
2000
2500
Aucilla, Static Test
Aucilla, Dynamic Test
1 min
15 min
60 min
QS0 =1021 kN (at t0 = 1day )
mS = 293.4 kN
Elapsed Time, t (days)
PileSideShearQS(kN)
Bullock et al. (1995) in FL
18” PSC, O-cell at bottom
(EOID Capacity plotted at 1 min)
FL Research Pile Setup – Log-linear Plot
= 225 tons
46. www.fugro.comwww.loadtest.com
where: A = Dimensionless setup factor
QS = Side shear capacity at time t
QS0 = Side shear capacity at reference time t0
fS = Unit side shear capacity at time t
fS0 = Unit side shear capacity at reference time t0
t = Time elapsed since EOD, days
t0 = Reference time, recommended to use 1 day
mS = Semilog-linear slope of QS vs. log t
Note: “A” is correlated to soil type (0.1 to 0.8) and
describes the capacity increase per log cycle of time
(relative to the reference capacity)
1log1log
00000
t
t
Q
m
t
t
A
f
f
Q
Q
S
S
S
S
S
S
Non-dimensional side shear setup:
47. www.fugro.comwww.loadtest.com
0.001 0.01 0.1 1 10 100 1000
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
2.2
Aucilla, Dynamic Test
Aucilla, Static Test
A = (mS / QS0) = 0.30
R2
= 0.99
1 min
15 min
60 min
Elapsed Time Ratio, ( t / t0 ) with t0 = 1 day
PileSideShearRatio,(Qs/Qs0)
Bullock et al. (1995) in FL
18” PSC, O-cell at bottom
+30%
+30%
+30%
Σ = +90% in 1 day
(or 9X 1 min capacity)
1-3d
+14 %
1-7d
+25%
1-28d +43% or
about half of
EOD-1d change
FL Research Pile – Non-dimensional Plot
48. www.fugro.comwww.loadtest.com
Example: Morgan City, LA - 30” PSC
• HPSI 2500, 300 bpf
• 30” PSC, 18” Void, 143 ft long
• Pile Setup Clay/Sand
• 950 ton O-cell
369 tons
at 1wk
416 tons
at 3 wks
464 tons
at 5 wksMax. O-cell Load 493 tons
Buoyant Pile Weight 29 tons
49. www.fugro.comwww.loadtest.com
Example: Busan, Korea - 24” PHC
• Prestressed Spun High Strength Conc.
• 24” OD, 16” ID, 103 ft long, 46 ft sections
• Sand / Clay / Sand
• 875 ton O-cell, 7 Strain Levels, Grouted
Buoyant Pile Weight 16 tons
Max. Side Shear 456 tons
Unit Side Shear 0.14 to 1.98 tsf
Max. O-cell Load 472 tons (944 ton test)
Max. End Bearing 155 tsf
50. www.fugro.comwww.loadtest.com
Example: Harrison County, MS - 66” Cylinder
• Conmaco 300, 128 bpf EOID
• 66” OD, 54” ID, 108 ft long
• Silt / Sand / Dense Sand
• 3000 ton O-cell, 4 Strain Levels
Buoyant Pile Weight 114 tons
Max. Side Shear 626 tons
Unit Side Shear 0.23 to 4.10 tsf
Max. End Bearing 45 tsf
Max. O-cell Load 740 tons (1480 ton test)
56. www.fugro.comwww.loadtest.com
• Test drilled shafts (wet/dry), CFA piles,
driven concrete or steel piles, barrettes
• Separates side shear & end bearing
• Very high load capability (321MN, St. Louis)
• Direct loading of rock socket
• Cost, safety, and space advantages
• No additional reaction system needed
• Doubles effective jack load
• Post-test grouting for production piles
O-cell Static Load Test Advantages
57. www.fugro.comwww.loadtest.com
Efficient O-cell Test Applications
• End bearing side resistance (use ultimate!)
• Restricted site access (remote location, existing
structures, environmentally sensitive, water)
• Prove capacity distribution (end bearing vs. side
resistance, unit side resistance)
• Accelerated construction schedule
• Large test loads required
• Site safety restrictions (personnel & equipment)
• Repeated tests (setup)
• Multiple test piles (but only one test frame)
• Compare with total cost of conventional testing
58. www.fugro.comwww.loadtest.com
• Pile preselected for testing
• Maximum load limited by the weaker of the
end bearing or side shear (add top load?)
• Top of pile not structurally tested
• Subtract buoyant weight of pile above O-cell
to calculate side resistance
• Must construct equivalent top load
movement curve
• use the sum of measured behavior
• use the sum of modeled behavior
• use finite element or t-z approach
O-cell Test Limitations
65. www.fugro.comwww.loadtest.com
Initial Design
• 9 m Rock Sockets (“typical”)
• Design side shear: 1.3 MPa (code)
O-cell Tests
• 2 Shafts with 1.5 m rock sockets
• Measured side shear: 2.7 MPa
Estimated vs. Actual Costs
• Final design: 4.5 m rock sockets
• Design FS = 3, Measured FS > 5
• Redesign FS > 2
• Fdn. Cost Est.: $18,000,000
• Testing cost: $ 255,000
• Fdn. redesign cost: $ 8,900,000
• Net Savings: $ 8,845,000
Cost Savings: Seacaucus NJ Transfer Station
66. www.fugro.comwww.loadtest.com
Job Number 566 775 835 381 056* 335 426 635
State CA FL NC NJ SC GA TX FL
Fdn. Estimate $850 $6,200 $32,500 $18,000 $160,000 $3,270 $8,500 $4,520
Fdn. Redesign $610 $4,980 $24,500 $8,900 $125,000 $3,003 $8,500 $7,232
Savings $240 $1,220 $8,000 $9,100 $35,000 $273 $0 -$2,712
Test Cost $79 $360 $2,000 $255 $7,500 $240 $95 $305
Net Savings $161 $855 $6,000 $8,845 $27,500 $33 -$95 -$3,017
Calculated FS 2.5 3.0 3.0 3.0 3.0 3.0 3.0 2.5
Measured FS 3.0 3.5 4.0 5.0 NA 3.5 9.5 0.8
Redesign FS 2.0 2.0 2.0 2.0 2.0 2.3 9.5 2.0
Foundation Savings After Testing Based On Actual Jobs Completed (Thousands)
• More than 70% of the FLT testing saved the client money
• Half of the remaining 30%, testing done too late to realize the savings
• Only a few estimates were so close not to allow a modified foundation
O-cell Tests Result in Project Cost Savings
67. www.fugro.comwww.loadtest.com
Reduce Cost by Reducing Uncertainty:
• Informed design (integrated investigation:
geophysics + insitu testing + sampling)
• Design verification (static & dynamic testing)
• Optimization (redesign)
• reduce length, size, number
• change type (driven, drilled, anchor)
• reduce cost and construction time ($$)
• FLT’s experience - savings 5X test cost
• Quality control testing to assure performance
& reduce remediation cost
68. www.fugro.comwww.loadtest.com
Deep Foundation Quality Control
• Driven Piles
• Blow Count, Hammer Energy, Dynamic Tests
• Drilled Shafts
• Control Slurry Properties
• Prepare Excavation Log
• Shaft Profile - Sonic Caliper
• Clean Shaft Bottom
– MiniSID, Downhole Camera
• Concrete Quality - Pile Integrity Test,
Crosshole Sonic Logging, Thermal, Gamma
• Verify Pile Capacity using RIM-cell
78. www.fugro.comwww.loadtest.com
RIM-CELL Applications
• PROOF TEST
• Install in every pile
• Load shafts to design load or
higher (2000 – 5000 psi)
• Eliminate uncertainty of site
variability
• Use higher LRFD factors
• Detect / remediate a “soft toe”
• POST-STRESSING
• Consolidate loose material at
shaft toe
• Engage end bearing without
losing side shear
• Limit settlement at service load
79. www.fugro.comwww.loadtest.com
RIM-CELL Assembly
RIM-cell fits inside reinforcing cage.
Hydraulic hoses and instrumentation
pipe installed on cage. Add strain
gages to isolate different soil strata.
RIM-cell welded to frame
below O-cell assembly for a
multi-level test shaft.
24” RIM-cell installed with
8 levels of strain gages
60” RIM-cell
80. www.fugro.comwww.loadtest.com
Excavate shaft and place cage with
RIM-cell. Large center opening
allows tremie pipe to pass. Low
cross-sectional area does not inhibit
concrete flow or trap weak material.
RIM-CELL Installation
60” RIM-cell installed into
78” rock socket
24” RIM-cell at toe of
an O-cell test shaft
20” RIM-cell installed
at the toe of 30” shaft
81. www.fugro.comwww.loadtest.com
Perform test after concrete obtains strength. Cement grout
is mixed and pumped through the hydraulic hoses into the
RIM-cell. Measured pressure is converted to load using
calibration factor of the RIM-cell. Load is increased to 1.2
to 1.5 times design load. Shaft movement is measured and
recorded. Grout will set up to restore integrity to the shaft.
24” RIM-cell Test Curve 36” RIM-cell Test Curve
RIM-CELL Testing
82. www.fugro.comwww.loadtest.com
Similar to O-cell with real-time
Load-Displacement plot during
test. Preliminary results
available same day as test.
RIM-CELL Reporting
60” RIM-cell
Schematic
section of
RIM-cell
shaft
Equivalent Top Load Plot
83. www.fugro.comwww.loadtest.com
RIM-CELL Limitations
• Internal friction unknown (but small)
• Preselect shaft
(install in every shaft, test as required)
• Reduced pressure vs. O-cell
(but large area)
• Typically will not test to failure
• Grouting required to restore shaft integrity
• Maximum load limited by the weaker of the
end bearing or side shear (add top load?)
• Top of pile not structurally tested
84. www.fugro.comwww.loadtest.com
Missouri Research
Project
• 24” bi-directional test piles
on two different sites
• Two piles on each site were
tested using RIM-cells
• 24” RIM-cells in 36” piles
• 20-30 feet deep shafts in
unweathered and weathered
shale
• Side by side comparison to
O-cell tests
24” (600mm) RIM-CELL Tests
86. www.fugro.comwww.loadtest.com
RIM-CELL Tests to Date
RIM‐cell
Size
Shaft Diameter
Max
Pressure
Max Cell
Load
Test Result
14" 24" 2500 psi 350 kips Side Shear Failure
14" 24" 1780 psi 250 kips End Bearing Failure
20" 30" 1530 psi 450 kips Side Shear Failure
20" 30" 1360 psi 400 kips Side Shear Failure
24" 36" 2560 psi 1100 kips RIM‐cell Capacity Maxed Out
24" 36" 1980 psi 850 kips RIM‐cell Capacity Maxed Out
24" 36" 640 psi 275 kips End Bearing Failure
24" 36" 1170 psi 500 kips End Bearing Failure
24" 30" 940 psi 400 kips Test stopped at 1" Expansion
36" 54" 475 psi 450 kips Side Shear Failure
60"
96"
(76"rock socket) 4950 psi 13,000 kips Test stopped at 1/2" Expansion
87. www.fugro.comwww.loadtest.com
Summary
• O-cell test proven for shafts and driven piles
• Compare overall cost and quality of test
results for conventional top-down testing
with O-cell testing
• RIM-CELL tests to verify production pile
capacity (QA/QC)
• Coming Attractions:
• New ASTM Standard
• Bigger piles, higher loads
• Mid-pile O-cell placement for spliced
concrete piles
• Mid-pile placement for steel pipe piles
88. www.fugro.comwww.loadtest.com
Summary
• Deep foundation design generally
conservative due to uncertainty.
• Correlate site characterization with
foundation design and testing. Reduce
project cost through more efficient design
and construction. Reduce uncertainty.
• Use a portion of the cost savings to fund the
testing and inspection needed for more
efficient design.
“The owner pays for a good site investigation
whether he does one or not.”