influence of deep foundation installation methods morgan nesmith
TRANSCRIPT
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Influence of Deep Foundation
Installation Methods Presented by:
Morgan NeSmith, PE Director or Engineering
http://www.berkelandcompany.com
To
2⁰ Congresso Internacional de
Fundaciones Profundas de Bolivia
Santa Cruz, Bolivia
May 2015
• Scope of Presentation
Precast Piles – steel, concrete
Cast-in-Place Foundations:
Drilled Shafts
Augered Cast-in-Place Piles / Continuous
Flight Auger Piles
Drilled Displacement Piles
Micropiles
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Factors Influencing Performance
• Installation Method
• Foundation Material (concrete, steel, wood)
Precast Piles
•Steel
•Pipe (open-end or closed-end)
•H-Pile
•Tapered
•Shell (mandrel driven)
Concrete
•Octagonal
•Square
•Cylinder
Timber
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Driven or
Vibrated
Piles
Driven Piles in Clay
http://user.engineering.uiowa.edu/~swan/courses/53139/notes/changes-in-soil-during-
pile-driving.pdf
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Driven Piles in Sand
http://user.engineering.uiowa.edu/~swan/courses/53139/notes/changes-in-soil-during-
pile-driving.pdf
Driven Piles in Sand
http://user.engineering.uiowa.edu/~swan/courses/53139/notes/changes-in-soil-during-
pile-driving.pdf
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Environmental
Effects Dynamic loading during
installation
- Vibrations: good for pile
installation, possibly very bad
for your neighbors
- Noise: not good for anything
except upsetting your
neighbors
- In saturated clay (nearly
incompressible in short term)
can heave ground and nearby
piles
Drilled Shafts
• With casing or slurry, drilled incrementally
Typically most useful for:
- ultra-high compressive loads (concrete compressive strengths up to 12,000 psi (83 MPa) or greater)
- high lateral loads
(requiring large amounts of reinforcing steel)
- geologies providing little shaft resistance where toe resistance is crucial (e.g. hard, shallow bedrock)
- where it would be beneficial to have direct connection from structure column to single foundation element
(bridges, structures where pile cap construction is not feasible)
• In last 15 years, line has blurred between when to use
single-pass augered / drilled piles and drilled piers / shafts
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Drilled Piers
Devon Energy - Oklahoma
Devon Energy WHQ
Drilled Piers
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Drilled Shaft – Example Reinforcing
Reinforcing
installed
PRIOR to
concrete
placement
Use concrete,
not grout,
typically
poured from
top or tremied
to bottom
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Shaft Typically Stabilized by
Casing or Slurry
Generally Neutral Displacement
(if constructed correctly!!!) Casing and slurry can smooth soil surface lowering the friction coefficient
between shaft and soil
Tremied concrete also has lower bond strength with soil than other cast-in-place
methods (grouted or pressure grouted)
Not many places in North America where shafts bear in soil only – mostly in
rock – however some in Chicago (hard OC clay locally called hardpan) and
Mississippi (large deposits of OC clay) where belled piers are often efficient
Many designers neglect shaft and only consider end bearing (possibly very,
very conservative)
Reinforcing is set after drilling but before concreting so is typically full length
whether the shaft needs it or not (lateral loads typically resolved in the upper
6-m to 12-m of shaft)
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Cast-in-place piles installed by
single-pass, rotary drilling processes
Terminology for Cast-in-Place Piles
Continuous Flight Auger European Screw Piles
ACIP
aka Augercast CFA
Intermediate (Partial) Displacement
Displacement Pile
Auger Pressure Grouted (APG) Pile System
• Cast-in-place piles grew out of pressure-
grouting processes at Intrusion-Prepakt,
late 1940s, early 1950s
• Patent granted to Raymond Patterson for
construction of cast-in-place piles by
pumping grout through a hollow-stem
auger.
• Licenses granted to Lee Truzillo and
Charles Berkel
“The Evolution of Cast in Place Piles”
November/December 2013 DFI Magazine
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• Gaspar Coelius granted patent for
cast-in-place “Screw” pile in 1960
Augered vs. Screwed or Displacement
Analogous to augered… .. And to displacement
From De Cock and Imbo, Transportation Research Record 1447
Excavated ACIP piles
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Stratigraphy?
Stratigraphy?
Residual soils
from soft to hard
to partially
weathered rock
(PWR = 100+
blows per 30 cm)
to bedrock
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(1) Stem augers hole
(4) Hollow stem
auger retracted
while grout pumped
into hole
(2) Grout pumped
under pressure
(3) Build up grout
head prior to
withdrawing auger
APG Pile Example Installation
2007 Berkel & Company
Cast-In-Place Pile
Seminar
(4) Hollow Stem
Auger is retracted
while grout is
pumped into hole
APG Pile Installation
(2) Grout is injected
under pressure
(1) Auger drills
hole
(3) Build up grout
head prior to
withdrawing auger
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Typical APG Pile Rig
Hollow Stem Auger
• Continuous flight auger
• 75 mm inside diameter pipe
• Auger diameters:
– Historical: 300 mm to 460 mm
– Typical: up to 610 cm = no problem
– Specialty: 760 cm to 1220 cm
• Auger section lengths: ~ 1 to 6 m
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JADE SIGNATURE - SUNNY ISLES BEACH, FL
90-cm Diameter (APG) Piles – 47-m Deep
Over 300 Installed in 20 weeks
To resist ~ 1000 metric tons compression
Auger Flights attached to Hollow Stem
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Drill Bits • Basic Bit - Pengo bit
• Basic Rock Bit - fitted with carbide teeth
• Clay Flight Bit - for clay soils
Leads Torque Arm
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Gearbox
• Hydraulically operated top
head drive
• Travels up and down the
leads
• Torques range from about 20
to 120 kN/m
• Weighs 1 to 5 metric tons
• Rotational speed ranges from
30 to 60 rpm
• Hydraulically
operated, positive
displacement piston-
ball valve pump
• Pump pressures
typically around 350
psi at pump outlet
• Stroke vols. typically
range from about 0.4
to 1.0 cubic feet per
stroke (up to 1.7)
• Grout hoses typically
2 to 3 inch diameter
• Can pump grout
several hundred feet
• Grout typically
delivered by ready mix
trucks
Grout Pump
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Typical Limited Headroom (LHR) Rig
• Used where overhead clearances
are at least 2.5 to 3 m
• Track-mounted or forklift mounted
drilling equipment
• Piles are drilled with auger sections
typically 1 to 3 m length
• Installation time longer than with
crane-mounted equipment (thus,
more expensive per foot
Neutral or
Negative
Displacement • If proper equipment not
used, stress release
can occur
• Potential for release is
greater in alluvial or
marine sands than in
residual soils and stiff
clay
• Potential for release is
greater in segmental
(low-head room) than
single auger
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Neutral or
Negative
Displacement • Can “suck” adjacent
piles if drilling too close
together
Fresh completed pile
Pile to be drilled
Maybe soil wants to displace
towards new pile being drilled as
horizontal confinement lowers
Pile to be drilled
Fresh pile may collapse into new
pile. Typically don’t drill adjacent
piles (closer than 6 diameters)
within 12 hours
ANCILLARY BENEFITS
Minimal Spoils
No Vibration
Low Noise
Easy to vary pile lengths to suit site conditions
Grouted bond to soils produces larger shaft
resistance than concrete-soil bond or driven
pile friction coefficients
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Fixed Mast Platforms
Drilled Displacement Piles
(full and partial displacement)
CFA (APG-FMC) Piles
Overview of Drilling
Platform and Sensors
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INSTALLATION PLATFORM
• 200 to 270 kN/m torque
• 18 to 36 metric tons downward force
• Fixed mast for stability, inclinometer
with display in operator’s compartment
• Grout pressure, measured at top of tools,
is displayed in operator’s compartment
• Real-time display of installation
parameters (depth, KDK pressure,
Installation Effort, grout pressure)
pressure
CAST-IN-PLACE PILES INSTALLED WITH A
FIXED MAST DRILLING PLATFORM (APG-FMC)
Wilkins, B., NeSmith, W.M,
Tebbenkamp, F., and Duncan, S. (2009)
Performance of Cast-in-place Piles
Installed with a Fixed Mast Drilling
Platform in Claystone – Glenrock WY
Proceedings of the DFI 34th Annual
Conference on Deep Foundations.
Kansas City MO, USA. 20 – 23 October
2010.
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CFA Example
• 6 to 9-m of weak, saturated,
compressible sand, silt and
clay
• Ground water at 1 – 2.5 m
depth
• Deep foundations for all major
units assumed from the outset
• Initial budget based on 1,600 x
9000-mm dia. drilled piers 3-m
into rock with temporary
casing.
• Considered drilled piers,
driven piles and auger cast
piles
Final decision:
** 600-mm dia. CFA pile w/
fixed mast platform**
Comments on CFA and Fixed Mast
Platforms
- Slower penetration and slower rotation with
fixed mast than with crane mounted APG piling
- Less spoils removed with CFA (maybe ~ 75%)
than with APG
- Slightly higher shaft values with fixed mast than
crane mounted systems
- Very economical to replace large pile caps or
drilled shafts
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Fixed-Mast Platform Crane-Mounted Platform
4’-0” +/-
30’-0” +/-
CONVENTIONAL ACIP TOOL
DRILLED DISPLACEMENT TOOL
INTERMEDIATE (PARTIAL)
DISPLACEMENT TOOL
APG and Displacement Tooling
Displacement leads to increased horizontal stresses (and densification) for higher shaft resistance in many soils
Grout/soil interface is a more effective load transfer interface than pre-cast or steel/soil
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Berkel Displacement Pile Tool
Figure 1. Berkel Displacement Tool
Stem becomes
progressively larger,
terminating in the
displacing element
+- 1-m, regular flighting,
300-mm to 460-mm diameter
Reverse flighting Displacing element. Same
diameter as the flighting
below
Stem, smaller than flighting
INSTALLATION METHOD
• Tool advances as a screw in low
to medium consistency soils.
• In dense soils, material
transported up the auger to the
displacing element. Material in
auger flights is compressed; thus
no stress relief in the zone
adjacent to the auger.
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INSTALLATION METHOD • When the target level has been
reached, pumping of grout is
begun. Grout pressure is
monitored by the operator Lift
off and withdrawal rate are
varied to maintain pressure
where possible.
• Tool is rotated during
withdrawal and material which
falls around stem is captured
and displaced.
• Typically get grout return only
after tip is at or near ground
surface.
Soil Improvement Aspects Of Displacement Pile
Installation • When displacement piles are installed in materials that exhibit
granular behavior, there is a significant increase in density in the vicinity of the piles
• The increase is most pronounced in loose to medium dense materials
• After a certain density, as the in-situ density of the materials increases, the density percentage change goes down
• The increase in density is additive-the more piles that are installed, the greater the increase
• Pressure grouted bond to soils produces larger shaft resistance than concrete-soil bond or driven pile friction coefficients
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2.1 METERS 2.1 METERS 1.8 METERS
1.8 METERS
0.46 M
0.46 M
0.46 M
46 CM BY 7.6 M COMPRESSION TEST PILE 46 CM BY 12.2 M EXTRA PILE
46 CM BY 12.2 M EXTRA PILE
46 CM BY 12.2 M REACTION PILE
Improvement from Drilled Displacement Tool Installation
“AMBIENT” CONDITION-3D FROM PILE
0
5
10
15
20
25
30
35
0 25 50 75 100 125 150
Qc, tsf
DE
PT
H,
ft
FINE SAND, TRACE TO SOME
SILT, OCCASIONAL THIN
SILT/CLAY LAYERS. AVERAGE
Qc = 3.1 MPa (32 tsf)
3.1 METERS
7.6 METERS
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AVERAGE CONE TIP RESISTANCE
COMPARISON OF CPT VALUES, 1D, 2D, 3D FROM PILE
0
5
10
15
20
25
30
35
40
0 25 50 75 100 125 150
CONE TIP VALUE, TSFD
EP
TH
, FEET
3D OUT 2D OUT 1D OUTAVERAGE CONE TIP
RESISTANCE FROM 3.1 M TO
7.6 M (10 FEET TO 25 FEET)
3.1 MPa (32 TSF,
N = 8 BPF)
6.5 MPa (68 TSF,
N = 17 BPF)
8.1 MPa (84 TSF,
N = 21 BPF)
FINE SAND, TRACE
TO SOME SILT,
OCCASIONAL THIN
SILT/CLAY LAYERS
3.1 METERS
7.6 METERS
CPT VALUES AT 1D, 2D, 3D FROM PILE
COMPARISON OF CPT VALUES, 3D FROM PILE AND CENTER OF GROUP
0
5
10
15
20
25
30
35
40
0 25 50 75 100 125 150
CONE TIP VALUE, TSF
DEP
TH
, FEET
3D OUT CENTER OF GROUP
3.1 MPa (32 TSF,
N = 8 BPF)
9.6 MPa (100 TSF,
N = 25 BPF)
3.1 METERS
7.6 METERS
AVERAGE CONE TIP
RESISTANCE FROM
3.1 M TO 7.6 M (10
FEET TO 25 FEET)
CPT VALUES AT 3D and CENTER OF GROUP
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ANCILLARY BENEFITS
Minimal Spoils
No Vibration
Low Noise
Easy to vary pile lengths to suit site
conditions
DOES THE BENEFIT
HOLD UP IN
RESIDUAL SOILS?
Some empirical
indications that shaft
resistance in medium
to dense sandy
residual soils are not
as high as expected
from marine, alluvial
and other younger
deposits.
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ORDER OF
INSTALLATION IN LARGE
GROUPS IS CRITICAL
DESIGN MODELS
UNDERESTIMATE GROUP
EFFECTS
Intermediate (Partial) Displacement
Pile System
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CONVENTIONAL ACIP TOOL
DRILLED DISPLACEMENT TOOL
INTERMEDIATE (PARTIAL)
DISPLACEMENT TOOL
APG and Displacement Tooling
Partial Displacement Auger Stem
Conventional ACIP Auger Stem
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Equipment/Process Summary
• Same installation platform as Drilled Displacement Piles-high torque, crowd
• Large diameter stem, small flight dia. (typically less than 2/3 ratio)
• Tooling is screwed into ground where possible (displacement), drilled in where necessary (excavation)
• Improve loose soils, limit stress relief in dense soils
• Target spoil is less than 75% of neat hole volume
• May be cast by volume (like APG piles) or by pressure (like Drilled Displacement piles)
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Efficiency Comparison to APG Pile
• Drilled displacement piles use more expensive
equipment
• Unit capacities from displacement systems can
be significantly higher than traditional APG piles
• Generally: If piles can be shorted and the
diameter can be decreased, displacement
systems can be more efficient (pending project
size)
Fixed-Mast Platform Crane-Mounted Platform
4’-0” +/-
30’-0” +/-
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Screening 1 – Insert the Screen
Screening 2 – Remove Foreign Objects
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Reinforcing Cage Placement
• In general, not as efficient as single-pass drilled or augered systems but:
– High capacity (particularly for size)
– Installation in limited access and/or low headroom
– Minimal disturbance/vibration to adjacent structures
– Capability to penetrate subsurface obstructions (very useful for rubble in urban fills and boulders in glacial till)
– Can case through voids (useful in limestone with large cavities)
Micro Piles (less than 300-mm dia)
• Refer to FHWA Micropile Design and Construction Guidelines and DFI / ADSC Micropile 2010 Seminar (also see local contractors!)
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Example Installations - Micro Piles
Copyright © 2009 PT. Geonusa Utama
• Drilling is somewhat neutral displacement. Post grouting and pressure grouting are positive displacement and the pressure grout to soil or rock bond is very high
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© 2008 Southwest Contracting Ltd
Example Pile Top - Micro Piles
Micro Piles at Dulles Airport
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Hollow Bar - Micropiles
Hollow Bar - Micropiles
Net Neutral Displacement – similar unit
shaft values as ACIP piles (so far)
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THE END – QUESTIONS?