micro pile seminar presentation
TRANSCRIPT
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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
4Give up?
5
Polish!!
6
This presentation is made by Con-Tech Systems Ltd
Josef (Joe) Alter
Sales and Engineering ManagerSouthwest Region USACon-Tech Systems Ltd24424 Manzanita DriveDescanso, 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
7CORPORATE OFFICE & CANADIAN PLANT
8
CTS Warehouses and Offices
in North America
Descanso, CANew 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 non-displacement 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 IBO SystemCTS/TITAN IBO 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 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-Pile1
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3
41- Hollow Bar
2- Final Grout W/C 0.45
3- Flushing grout W/C 0.7 Soil Cement mix
4- Ground improvement
Hollow TITAN Bar Ultimate Yield
Dout/Dinin
2kips kips in
mm mm2
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
Steel
AreaRod Size
Load Capacity Nominal
Dia.
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Drill Bit
Hollow Titan Bar
Centraliser
Coupling
Bearing Plate
Hex Nut
Pipe Sleeve
CTS/TITAN Hollow Bar System
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Clay Bit: Clay, sand-mixed Ground without Boulders < 50 S.P.T
Carbide-Bit:
For controlled directional drilling (tolerance < 2% of the length)
Button Bit:
Dolomit, Granite, Sandstone; strength 70-150 MPa
Carbide Step Bit:
Weathered Rock, Phylit, Slate, Shale; strength < 70 MPa
Carbide Button Bit: Reinforced Concrete or Rock, strength > 70 MPa
Cross Cut Bit: Dense Sand with Gravel and small Boulders > 50 S.P.T
Drill Bit Selection
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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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Soil/Cement mix
Drill Bit
Stabilized and densified Soil
Natural Soil
Hollow Bar
2,0 x d for medium to coarse gravel1,5 x d for sand und sandy gravel1,2 x d for cohesive soil (clay)1,0 x d for weathered sandstone, Phylit, slate
D >
d Drill Bit Diameter
Grout cover
min. 20 mm
TITAN Hollow bar Micro Pile
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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
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STRUCTURAL DESIGN OF MICROPILE
UNCASED LENGTH
From FHWA Design Guidelines
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Structural Design of Uncased
Pile (IBC)
[ ])4.0()33.0('
barbarygroutgroutcallowablec AFAfP ×+×=−−−
barbaryallowablet AFP ×=−−
6.0
Compression
Tension
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Load Test Structural Capacity
[ ])()85.0('
barbarygroutgroutcncompressioult AfAfP ×+×=−−−
[ ]barbarytensionult AfP ×=−−
Micropile Geotechnical Capacity
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Geotechnical Capacity (ASD)
αbond = grout to ground ultimate bond strength
FS = factor of safety applied to the ultimate
bond strength
Db = diameter of the drill hole
Lb = 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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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.
Summary
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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
65VS 100
Water gauge with holding tank
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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 far-reaching 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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References
Standard industry reference with detailed examples of micropile design and
applications
Micropile Design and
Construction Reference Manual, 2005, FHWA NHI-05-039
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FHWA Review and Assessment of Hollow Core Soil Nails for Transportation Projects
Soil Nail Design and
Construction State-of-the-Practice, April, 2006
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Provides guidelines for Buckling calculations of micropiles
ADSC-IAF Document
Buckling 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