Introduction to Micropile Design 101 - Arizona Ram Jack

Introduction to Micropile Design 101
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Presentation for
Arizona Ram Jack Seminar
Introduction to micropile analysis,
design, and construction with
TITAN Micropiles
January 15, 2010
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Agenda
• Introduction to Con-Tech Systems Ltd
• TITAN Injection Bore (IBO) Anchor System
• Corrosion Protection
• Micropile Design
• Micropile Geotechnical Capacity
• Micropile Structural Capacity
• Sample Design Calculation for TITAN Micropile
• Micropile Testing
• Installation Equipment
• The ADSC
• References
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Give up?
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Polish!!
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This presentation is made by Con-Tech Systems Ltd
Josef (Joe) Alter
Sales and Engineering Manager
Southwest Region USA
Con-Tech Systems Ltd
24424 Manzanita Drive
Descanso, CA 91916
TEL: 619-659-9931 FAX: 619-659-9932 CELL: 619-894-2616
For a more detailed list of products and systems,
please refer to our Web Site:
www.contechsystems.com/cts-cd
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CORPORATE OFFICE & CANADIAN PLANT
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CTS Warehouses and Offices
Descanso, CA
in North America
New Port
Richey, FL
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Micropile Definition
• A micropile is a small-diameter (typically less than
300 mm (12 in.)), drilled and grouted nondisplacement
pile that is typically reinforced.
• A micropile is constructed by drilling a borehole,
placing steel reinforcement, and grouting the hole.
• Micropiles can withstand relatively significant axial
loads and moderate lateral loads.
• Micropiles are installed by methods that cause
minimal disturbance to adjacent structures, soil,
and the environment.
• They can be installed where access is restrictive
and in all soil types and ground conditions.
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Where to Consider Micropiles
• project has restricted access or is located in a
remote area;
• required support system needs to be in close
pile proximity to existing structures;
• ground and drilling conditions are difficult (e.g.,
karstic areas, uncontrolled fills, boulders);
• pile driving would result in soil liquefaction;
• vibration or noise needs to be minimized;
• hazardous or contaminated spoil material will be
generated during construction; and
• adaptation of support system to existing
structure is required.
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Typical Micropile Construction
Sequence Using Casing
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Construction Type Classification
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TITAN Injection Bore Anchor
System and Components
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CTS/TITAN CTS/TITAN IBO IBO System System
The Flushing/Stabilizing Grout is injected
through the inside of the hollow Titan bar and
exits through the venturi holes in the Drill-Bit.
Flushing/Stabilizing Grout stabilizes the
borehole and flushes the cuttings out of the
hole.
The hollow bars with a typical length of 3m
are coupled and drilled to required depth.
After reaching the final depth, the pressure
injection continuous.
With the continuous Injection stage,
Injection stage, the
flushing grout will be replaced with a richer
grout.
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Typical cross
section of an
exhumed IBO®
Micro-Pile
1- Hollow Bar
2- Final Grout W/C 0.45
3- Flushing grout W/C 0.7 Soil Cement mix
4- Ground improvement
1
4
2
3
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Steel
Hollow TITAN Bar Rod Size
Area Ultimate Yield
Dout/Din
in 2
Load Capacity Nominal
Dia.
kips kips in
mm mm 2
kN kN mm
30/16 0.59 49.5 40.5 1.18
382 220 180 30
30/14 0.61 58.5 49.5 1.18
395 260 220 30
30/11 0.69 72.0 58.5 1.18
446 320 260 30
40/20 1.13 121.2 96.7 1.57
726 539 430 40
40/16 1.36 148.4 118.1 1.57
879 660 525 40
52/26 2.07 208.9 164.2 2.05
1337 929 730 52
73/53 2.53 260.9 218.1 2.87
1631 1160 970 73
103/78 4.88 513.2 404.8 4.06
3146 2282 1800 103
103/51 8.53 778.1 618.4 4.06
5501 3460 2750 103
130/60 14.79 1785.5 1180.6 5.12
9540 7940 5250 130

CTS/TITAN Hollow Bar System
Drill Bit
Hollow Titan Bar
Centraliser
Coupling
Bearing Plate
Hex Nut
Pipe Sleeve
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Clay Bit:
Cross Cut Bit:
Button Bit:
Carbide-Bit:
Carbide Button Bit:
Carbide Step Bit:
Drill Bit Selection
Clay, sand-mixed Ground without
Boulders < 50 S.P.T
Dense Sand with Gravel and small
Boulders > 50 S.P.T
Weathered Rock, Phylit, Slate,
Shale; strength < 70 MPa
Dolomit, Granite, Sandstone;
strength 70-150 MPa
Reinforced Concrete or Rock,
strength > 70 MPa
For controlled directional drilling
(tolerance < 2% of the length)
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Drill Bit Selection Chart
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Full strength
Couplers, to develop
the ultimate strength
of the bar
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Centralizers
to allow for
grout
passage
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Spherical hex nuts,
2 nuts for tension/compression piles,
(bearing plate with top and bottom nut)
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Double nut and
plate connection
to grade beam
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Corrosion Protection
• Epoxy Coating
• Metalizing
• Sacrificial steel
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Sacrificial Steel Method
TITAN 40/20 hollow bar over 60 years
Allowable Design Load: 72.7 kips
• No Ground Aggression:
6.8% Loss = 72.7 kips * 0.932 = 67.8 kips
• Mild Ground Aggression:
11.2% Loss = 72.7 kips * 0.888 = 64.6 kips
• Aggressive Ground Aggression:
18.4% Loss = 72.7 kips * 0.816 = 59.3 kips
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Sacrificial
Steel
Method
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TITAN Hollow bar Micro Pile
D >
Grout cover
min. 20 mm
d
Drill Bit Diameter
Natural Soil
Stabilized and
densified Soil
Drill Bit
Hollow Bar
Soil/Cement mix
2,0 x d for medium to coarse gravel
1,5 x d for sand und sandy gravel
1,2 x d for cohesive soil (clay)
1,0 x d for weathered sandstone, Phylit, slate
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Micropile Design
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Micropile Design
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Micropile Design
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Micropile Structural Capacity

STRUCTURAL DESIGN OF MICROPILE
UNCASED LENGTH
From FHWA Design Guidelines
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Structural Design of Uncased
Compression
Pile (IBC)
[ ]
P ( 0.
33f
'
× A ) + ( 0.
4F
× A )
= c−allowable
c−grout
grout y−bar
Tension
P ×
t−allowable
= 0.
6 Fy−bar
A
bar
bar
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Load Test Structural Capacity
[ ]
P ( 0.
85 f
'
× A ) + ( f × A )
ult−compression
ult −tension
= c−grout
grout y−bar
[ ] f A
P ×
= y−bar
bar
bar
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Micropile Geotechnical Capacity

Geotechnical Capacity (ASD)
α bond = grout to ground ultimate bond strength
FS = factor of safety applied to the ultimate
D b
L b
bond strength
= diameter of the drill hole
= bond length
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Grout to Ground
Adhesion Strength
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Ultimate Bond Stress for Rock to
Grout as Recommended by PTI
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Ultimate Bond Stress for Cohesionless
Soils to Grout as Recommended by PTI
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Ultimate Bond Stress for Cohesive Soils
to Grout as Recommended by PTI
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Sample Micropile Design
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Bond Stress for TITAN Anchors as
Recommended by ISCHEBECK
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Sample Micropile Design
2
2
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Sample Micropile Design
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Summary
The hollow bar, used as both drill rod and
grout conduit, is left in the ground as
reinforcing steel to transmit compressive,
tensile, and lateral forces.
Hollow bars have a larger section
modulus than solid bars.
With the continuous tremi-grout injection,
100% grout cover and therefore excellent
corrosion protection is accomplished,
similar to reinforcing steel in concrete.
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Micropile Testing Procedures and
Guidelines
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Micropile Load Tests
There are four types of test loading:
•compression test
•uplift or tension test
•lateral-load test
•torsion-load test
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Test Procedures for Ground Anchors
•American Society for Testing and Materials ASTM
D1143/D1143M-07. Standard test methods for deep
foundations under static axial compressive load.
•American Society for Testing and Materials ASTM
D3689-07. Standard test methods for deep foundations
under static axial tensile load.
•PTI. (2004). Recommendations for prestressed rock and
soil anchors. Post-Tensioning Institute, Phoenix, AZ.
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Schematic of Compression Load Test Arrangement
(ASTM D1143/D1143M-07)
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Schematic of Tension Load Test Arrangement (ASTM D3689)
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Schematic of Lateral Load Test Arrangement (ASTM D3966)
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Micropile Tension Test
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Micropile and Anchor Testing
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Exhumed TITAN Anchors
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TITAN
Anchor
Drilled
Through
Boulder
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Injection Bore Strengths - Titan
• Fully supported hole during drilling
• Jetting action to over ream hole –
uniformly or in isolated areas
• Penetration of the grout beyond the bit
diameter or cut hole limit
• Readily adaptable length and injection
process to meet site variability conditions
• Somewhat self adjusting to variable soil
conditions
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Equipment For Grouting and Drilling
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VS 100
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Water gauge with holding tank

Neat Water/Cement Grout Mix:
Potable Water
Cement Type I, II or III
Drilling and Flushing - W/C = 0.7-1.0
Final Grout - W/C = 0.45
minimum strength at 28 days = 3,000 PSI.
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Obermann VS-63
High speed high
shear-colloidal
mixer with two
mixers, one for
the thinner
flushing grout
and one for the
final grout.
Water/cement
dosing system
and double
plunger pump;
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The use of an
automatic logging
system for
measurement,
recording and
documentation of
grout volume and
pressure is also
recommended.
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The ADSC
• International Scope;
– headquartered in Dallas, Texas
• 9 Regional US Chapters
• Extensive membership list, significant
annual operating budget with a farreaching
agenda
• Representing the Drilled Shaft, Anchored
Earth Retention and Micropile construction
technologies.
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Work of the ADSC includes
– Establishing standards & specifications for the
industries it serves
– Promoting ethical practice
– Conducting design, construction and inspection
seminars, worldwide
– Developing technical materials
– Funding and conducting research
– Providing a forum for technology transfer
– Stimulating industry growth
– Interfacing with corresponding industries and
agencies (FHWA, OSHA, DOTs, etc.)
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Available thru the ADSC
• Network of Experienced and Proven Contractors,
Design Professionals and Material Suppliers!
• Training Opportunities
– Regional seminars,
– Videos and other media
– Design, Safety, Personnel Training Materials
• Technical Resources
– On-Line Technical Library
– Technical Papers
– Design Manuals
– Foundation Drilling Magazine
– Specifications
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Micropile Design and
Construction Reference
Manual, 2005, FHWA
NHI-05-039
Standard industry
reference with
detailed examples of
micropile design and
applications
References
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Soil Nail Design and
Construction State-ofthe-Practice,
April, 2006
FHWA Review and
Assessment of Hollow
Core Soil Nails for
Transportation Projects
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ADSC-IAF Document
Buckling of Micropiles
Provides guidelines for
Buckling calculations
of micropiles
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PTI. (2004).
Recommendations
for prestressed
rock and soil
anchors. Post-
Tensioning
Institute. Phoenix,
AZ.
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A History of
Micropiles and
Early Applications
from the Inventor
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Web Resources
• http://www.fhwa.dot.gov/engineering/geotech
/library_listing.cfm
• http://www.dfi.org/
• http://www.adsc-iafd.com
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Questions
Comments
Observations
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Thank You for Your Attention
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