Large Open Ended Pipe Piles Cylinder Pile Production · 3 A well designed driving system prevents...
Transcript of Large Open Ended Pipe Piles Cylinder Pile Production · 3 A well designed driving system prevents...
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Large Diameter Open Ended Pipe Piles
Frank Rausche, GRL Engineers Day, 2015Frank Rausche, GRL Engineers Day, 2015
© 2014 Pile Dynamics, Inc.
Topics
• Pile Properties
• Cylinder and pipe pile details
• Damage potential
• The FHWA Synthesis
• Cylinder pile topics
• Plug formation, a study
• Very large pile example
• Summary
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Steel Pile Properties• Rolled pipe diameters unlimited; spiral welded 10’
• Wall thickness 1” max for spiral weld
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Cylinder Pile Production
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Spinning, Post‐tensioning
Photos: courtesy Don Theobald, Gulf Coast Prestress
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Moving and Installing
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Cylinder Pile Properties
• Sizes:– US: 36x5, 54x5, 66x6”
(910x130, 1370x130/150, 1680x150 mm)
– Other countries: 16, 20, 30” (400, 500, 750 mm) Concrete strengths:
– US: 6 to 8 ksi(42 – 55 MPa)
– Other countries: same or more
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Driving systems
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Add‐On
Stabbing Guide
Temp. Pile Top
Pile Stabbing
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Static Bending Stresses
WH
Wp
Jacket Leg
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Driving systems
•Leads which do not sway, bend piles
•Hammer cushion: man made material, uniformly worn
•Helmet: well fitting, evenly striking surface; skirt not to apply horizontal forces
•Pile cushion: plywood stacks, engineered and well assembled
Driving systems
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A well designed driving system prevents bending stresses,eccentricities
Photograph: Courtesy Massman Construction
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ProblemsVertical Cracking Top Damage
Pile top damage due to:
• Uniform driving stresses plus prestress
• Hammer eccentricity and misalignment
• Limited effectiveness of hoop reinforcement
• Complex stress state at pile top
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Pile top forces
Helmet lateral forceHelmet lateral force
Grout pressure
Strand anchoring forces
Cushion expansion force
Eccentric, misaligned driving forcesEccentric, misaligned driving forces
Non-uniformly worn cushion
Poorly fitting helmet
Concrete quality problemsConcrete quality problems
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Pile top forces
Internal guide problems
Internal helmet lateral force
Internal helmet lateral force
Ouch
Non-uniformly worn cushion Non-uniform
cushion force
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Tensile stress pile damage
• Low ram/pile weight ratios cause for high tension stresses both when driving is easy andwhen it is very hard
• Additional bending stresses particularly in battered pile driving
• High tension/compression stress cycles cause small tension cracks and eventually damage, particularly under water
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Recommendations for damage prevention
• Reduction of allowable driving stresses from 85% to 66% of strength minus prestress
• Monitoring of driving stresses
• Well engineered driving system
• Well aligned hammer ‐ pile to prevent bending
• Careful grouting and prestressing
• High quality concrete and curing
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Bending / Local Stress concentrations
… due to
• Hammer Weight
• Pile Batter
• Barge/crane/lead motion
add to
• Driving and pre‐stress, post‐tensioning stresses
also
• Non‐uniform soil resistance adds to unpredictable additional stresses
Ouch
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The Synthesis
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Some relevant statements
• Large diameter open ended piles (LDOEPs) are steel or prestressed concrete cylinders 36” or larger in diameter which can provide large axial and lateral resistance even in relatively poor soil conditions
• Load and Resistance Factor Design (LRFD) methods for piles were calibrated using piles with a diameter of 24” or less
• Recent or current projects with LDOEPs San Francisco –Oakland Bay Bridge, Woodrow Wilson Bridge, Tappan Zee Bridge, Kentucky Lakes Bridge, .. in New York which is currently under construction
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SynthesisResults
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SynthesisResults
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SynthesisResults
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Synthesis Results
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Synthesis Results
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Synthesis Results
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Synthesis results
McVay 2004
66” dia OE Cylinder pileDetermined critical g‐level of 15 g’s for plug slipping
Static: 1962 kipsR‐total CAPWAP – restrike with 0 set and no superposition:
1266 kips
(Note: Superpostion uses end bearing from EOD and Shaft resistance from BOR)
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Synthesis resultsAlaska DOT – 12 to 48” dia piles
Developed a design method based on CAPWAP results.
The proposed relationships were used to predict pile resistance on a project with 29 monitored piles driven into silt-rich deltaic deposits.
Dickenson reported “Overall, the agreement between the predictions and the CAPWAP results was good to excellent, and the proposed method provided much more reliable ranges of estimated pile resistance than obtained using widely-adopted, standard of practice procedures.”
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Synthesis results
A Comparison of Dynamic and Static Pile Test Results (OTC, Stevens 2013):
48” dia OEPipe Piles at 40’ and 65’ depth Uplift Static: 1180 and 2530 kips
R‐shaft CAPWAP: 1290 and 2530 kips
78” dia OEPipe Piles at 110’Uplift Static: 5875 kips
R‐shaft CAPWAP: 5930 kips (extrapolated to 53 days using pore water pressure measurements)
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Synthesis resultsKentucky Lakes, Terracon
48 and 72” dia OEpipe piles with 1 to 2” wall thickness48” plug models after Paikowsky
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Synthesis resultsKentucky Lakes, Terracon
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Synthesis results: Kentucky Lakes
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Synthesis results: Kentucky Lakes
• For the dynamic records where radiation damping was applied, the modelgenerally resulted in a significantly better signal match quality, indicating theradiation damping allows CAPWAP to better model the signals recorded by thedynamic pile testing equipment.
• The pile resistances calculated with CAPWAP using the radiation dampingmodel also generally produced higher end bearing resistance values than theCAPWAP models without the radiation damping. It appears that the radiationdamping model is better suited for estimating the end bearing component of thepiles when less pile set is experienced per hammer blow. This is the case whenthe constrictor plates are engaged on the dense granular soils.
• Wave equation analyses indicated that plugged piles would have high stresses.Additionally there was concern that localized high stresses might be encountereddue to the presence of the chert. Testing on the piles typically did not approachas high values as expected.
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US 378 Bridge over Pee Dee River (South
Carolina) S&ME
Two 54” diacylinder piles
To monitor the formation of a plug in the interior of the pile, a simple device called apile plug monitoring device (PPMD) was constructed. The PPMD consisted of leadweights attached to a 100 foot fiberglass measuring tape. The weights would fall to thetop of the soil column inside of the piles, allowing the distance to the soil to becomputed. Access to the interior of the pile was made through a vent hole near the topof the pile. The PPMDs were read intermittently throughout test pile installation. The data showed that soil was rising inside both piles during driving, indicating that disturbed soil and water was accumulating in the pile rather than a pile plug forming and traveling down with the pile.
Synthesis results
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Synthesis results
US 378 Bridge over Pee Dee River (South
Carolina) S&ME
!
!
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Longitudinal cracks
Potential causes:• Poisson’s effect and/or insufficient hoop reinforcement
– (may not be a problem)
• complex stress state at pile top or pile bottom• concrete and/or manufacturing defects• internal hydrostatic water pressure
– (provide water escape hole)
• internal excess soil or pore water pressure– (wash out plug, bail out water!)
• internal dynamic air/water pressure
CANNOT BE DETECTED BY PDA
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Static Plugging
Internal Friction (from arching?) on plug
Internal friction on pipe
End Bearing
Internal soil column
Pile wall
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Dynamic Plugging?
Internal Friction on plug
Internal friction on pipe
End Bearing
Inertia force
Soil column
Pile wall
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Dynamic Considerations:Plug inertia vs internal resistance
Assuming a plug length equal to 1, 3 and 5 diameter pile diameters
Assuming 100 g’s steel acceleration
The graph shows internal friction and inertia (no end bearing) 0
1000
2000
3000
4000
5000
12 24 36 48 60 72 84 96
Iner
tia
or
Inte
rnal
Res
ista
nce
(k
ips)
Diameter (Inches)
1D Plug Inertia
3D Plug Inertia
5D Plug Inertia
1D Plug Ri
3D Plug Ri
5D Plug Ri
Conclusion: under these VERY simplified circumstances a plug will slip if the diameter is more than ~40 inches
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Unplugged pile toe accelerationConcrete cylinder pile
Figure 3: Relative Toe Acceleration for Unplugged Cylinder Piles
30
40
50
60
70
80
90
100
40% 50% 60% 70% 80% 90%
Analyzed Stroke Relative to Rated Stroke
To
e A
cce
lera
tio
n (
g's
)
Hydraulic 8" Cushion
Hydraulic 12" Cushion
Hydraulic 15" Cushion
Diesel 8" Cushion
Diesel 12" Cushion
Diesel 15" Cushion
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-10000
-8000
-6000
-4000
-2000
0
2000
4000
6000
8000
10000
12000
0 10 20 30 40 50
Time (ms)
Fo
rce
(kN
)
Inertia Force
Toe Resistance on Plug
Total
Lp
qu
fs
Soil inertia and toe resistance on plug
Lpfs
Fi
qtoe
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Loss of Resistance Due to Pile DrivingLoss of Resistance Due to Pile Driving
• Sand porewater pressure changes
• Liquefaction
• Clay remolding, thixotrophy
• Other?
• Arching in granular soils• not during driving at toe: reduced end bearing
• During driving at shaft: reduced friction
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Loss of friction due to pile lateral motions
Pile
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Pile
Loss of friction due to pile lateral motions
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Loss of friction due to arching
Soil-pile interface with reduced effective
stresses
Pile
Compressed, higher density soil
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Friction fatigue considers that the SRD is equal to the LTSR at the pile toe and decreases exponentially above the toe (loss depends on the distance from the toe)
0
10
20
30
40
50
60
70
80
90
100
0 200 400 600
Dep
th b
elo
w m
ud
line
in m
Resistance per1 m segment in kN
Rinitial (LTSR)
Rresidual (SRD)
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Friction Fatigue: Loss of resistance
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Friction Fatigue: Loss of resistance
0
10
20
30
40
50
60
70
80
90
100
0 200 400 600
Dep
th b
elo
w m
ud
line
in m
Resistance per1 m segment in kN
Rinitial (LTSR)
Rresidual (SRD)
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0
10
20
30
40
50
60
70
80
90
100
0 200 400 600
Dep
th b
elo
w m
ud
line
in m
Resistance per1 m segment in kN
Rinitial (LTSR)
Rresidual (SRD)
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Friction Fatigue: Loss of resistance
• Friction fatigue considers that the SRD is equal to the LTSR at the pile toe and decreases exponentially above the toe (loss depends on the distance from the toe)
• In contrast, the standard GRLWEAP approach assumes full loss of resistance in a particular soil layer.
0
10
20
30
40
50
60
70
80
90
100
0 100 200 300 400 500
Dep
th b
elo
w m
ud
line
in m
Resistance per1 m segment in kN
25 m depth 50 m depth
75 m Depth
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Friction Fatigue: Loss of resistance
Rinitial (LTSR)
Rresidual (SRD) 0
10
20
30
40
50
60
70
80
0 0.2 0.4 0.6 0.8 1 1.2
Dis
tan
ce f
rom
Bo
tto
m
Long Term Capacity Multiplier
Example: fs=5, Ll=50, fo=0.001; fL= 0.05
fL
Ll
• Resistance Ratio, fs (say 5?)fs = Rinitial/Rresidual
• Degradation distance, Ll (Limit Length, 20 to 150 m)
• Undegraded distance, fL say 0.05)
• Exponent for degradation shape, fo (say 0.001)
See Alm and Hamre, 2001. Soil model for pile driveability based on CPT interpretation. Proc. 15th Int Conf. on Soil Mechanics and Geotechnical Engineering, Istanbul
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GRLWEAP Friction Fatigue Approach
In Preparation of an improved GRLWEAP/CAPWAP model let us consider what we must calculate:
Displacement of steel and plug Velocity of steel and plug
Unknowns to be determined: fste, qste
fsti, qsti
rst, qst
rpl, qp
plus damping
External and Internal Pipe Friction, fsti, qsti,fste, qste
rP, qp,t
Plug Wt
Steel
Plug
Plug Inertia
rt,St qt
Plug modeling
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Simplified model: single plug mass Unknowns to be determined: fste, qste, fsti, qsti, rpl, qp plus damping
Pipe Pile Steel onlyPlug
Wit Full End Bearing
Acceleration from GW - easy drivingDiameter inch D 18Wall thickness inch t 0.5Area in^2 A 27.489Pile segment length inch dL 40Soil plug length inch dPl 72.000Segment weight above toe segment k w1 0.313mass above last pile segment k/f/s2 m1 0.001weight of last pile segment k w2 0.313mass of last pile segment k/f/s2 m2 0.001weight of plug k wp 0.945mass of plug k/f/s2 mp 0.002internal limit friction F-int. ksf 5.000internal limit friction F-int. kips 133.518unit res against steel ru-toe-s ksf 250.000unit res against steel rutoe-s ksi 1.736Steel toe resistance ult Rutoe-s k 47.724unit res against plug ru-toe-p ksf 125.000unit res against plug rutoe-p ksi 0.868Soil toe resistance Rutoe-p k 196.931q steel toe qs inch 0.100q soil plug qp inch 0.283Rel. plug length Lplug diameters 4.000q internal friction qfi inch 0.100Note, this model uses unloading =loading quake as per GRLWEAP
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Example 18 inch pile
Pile is rigidly linked to plug –displacements are the same.
Easy driving record
-200
0
200
0 5 10 15 20 25 30
Vel
in
inch
/s
ms
v steel
v steel
-0.4
0.1
0.6
1.1
0 5 10 15 20 25 30Dis
pl.
in in
ches
Time in ms
d steel
d steel
-500
0
500
0 5 10 15 20 25 30
Acc
eler
atio
n in
g's
Time in ms
a steel
a steel
0
50
100
150
200
250
300
0 5 10 15 20 25 30
forc
e -
kips
Time in ms
Plug rigidly linked to steel
R steel Rplug-no slip Rtotal-no slip
INPUT - Easy driving record
Example 18 inch pile
Plug is linked to steel pipe with an elasto‐plastic spring (R‐int, q‐int)
-300
-200
-100
0
100
200
0 5 10 15 20 25 30
Vel
in
inch
/s
msv steel v plug
-0.4
0.1
0.6
1.1
0 5 10 15 20 25 30Dis
pl.
in in
ches
Time in msd steel d plug
-400
-200
0
200
400
600
0 5 10 15 20 25 30
Acc
eler
atio
n in
g's
Time in msa steel a plug
-300
-200
-100
0
100
200
300
0 5 10 15 20 25 30
forc
e -
kips
time - ms
All forces
R steel F-int Rplug Inertia
INPUT - Easy driving record
Example 18 inch pilePile is rigidly linked to plug –displacements are the same.
0
20
40
60
80
100
120
140
160
180
200
3 8 13 18 23 28 33
forc
e -
kips
Time in ms
Rigidly linked plug
R steel Rplug-no slip Rtotal-no slip
-1000
0
1000
3 8 13 18 23
Acc
eler
atio
n in
g'
s
Time in ms
a steel
a steel
-200
3 8 13 18 23inch
/s
ms
v steel
v steel
-0.2
3 8 13 18 23inch
es
ms
d steel
d steel
INPUT - Hard driving record
Example 18 inch pile
Plug is linked to steel pipe with an elasto‐plastic spring (R‐int, q‐int)
-500
0
500
3 8 13 18 23
Acc
eler
atio
n in
g'
s
Time in msa steel a plug
-200
0
200
3 8 13 18 23inch
/s
msv steel v plug
-0.2
-0.1
0
0.1
0.2
3 8 13 18 23inch
es
ms
d steel d plug
-150
-100
-50
0
50
100
150
200
3 8 13 18 23forc
e -
kips
time - ms
R steel F-int Rplug Inertia
INPUT - Hard driving record
Example 18 inch pile
Plug is linked to steel pipe with an elasto‐plastic spring (R‐int, q‐int)
-500
0
500
3 8 13 18 23
Acc
eler
atio
n in
g'
s
Time in msa steel a plug
-200
0
200
3 8 13 18 23inch
/s
msv steel v plug
-0.2
-0.1
0
0.1
0.2
3 8 13 18 23inch
es
ms
d steel d plug
INPUT - Hard driving record
-150
-100
-50
0
50
100
150
200
3 8 13 18 23forc
e -
kips
time - ms
R steel F-int Rplug F-pile Rs+Rp
Conclusion from simplified plug model
• The study clearly shows that the full activation of the toe resistance against the plug is as important as plug slippage when attempting to mobilize and calculate full resistance
• The model has to consider
– the internal friction on plug and pile
– the plug compressibility and mass
– different quakes and unit resistance values for annulus when not plugging and unit toe resistance for plugged analysis
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21m dia Steel; APE Octagon; Photo Galerie
A Word about Very Large Pipes and Vibratory Analysis
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4 APE 600B12x0.25 m dia concrete shell
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GRLWEAP Calculated of Rate of Penetration
Yangtze Caisson:
12x.25 m concrete pipe, 25 m long
4 APE 4B hammers (683 kg m, 20 Hz, 3000 kW); 8 clamps + beams
Clay, silty Sand; N at most 3
Shaft resistance (inside and out) 10 kPa
Analyzed at 80% and 100%
Toe resistance 90 kPa
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GRLWEAP Calculated of Rate of Penetration
Yangtze Caisson
0
2
4
6
8
10
12
0 50 100 150 200
Penetration Speed - mm/s
Dep
th in
m
80% Shaft Res: 30 s 100% Shaft Res: 66 s
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Thank You
Discussion?