Introduction to Micropile Design 1011 Presentation for Arizona Ram Jack Seminar Introduction to micropile analysis, design, and construction with TITAN Micropiles January 15, 2010 2 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 3 Give up? 4 Polish!! 5 . please refer to our Web Site: www.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.contechsystems.com/cts-cd 6 . CA 91916 TEL: 619-659-9931 FAX: 619-659-9932 CELL: 619-894-2616 For a more detailed list of products and systems. CORPORATE OFFICE & CANADIAN PLANT 7 . CA New Port Richey. FL 8 .CTS Warehouses and Offices in North America Descanso. • Micropiles are installed by methods that cause minimal disturbance to adjacent structures. placing steel reinforcement.Micropile Definition • A micropile is a small-diameter (typically less than 300 mm (12 in. 9 . • Micropiles can withstand relatively significant axial loads and moderate lateral loads. • They can be installed where access is restrictive and in all soil types and ground conditions.)). and grouting the hole. • A micropile is constructed by drilling a borehole. drilled and grouted nondisplacement pile that is typically reinforced. soil. and the environment. • ground and drilling conditions are difficult (e.Where to Consider Micropiles • project has restricted access or is located in a remote area. • hazardous or contaminated spoil material will be generated during construction. and • adaptation of support system to existing structure is required. boulders).. uncontrolled fills. • pile driving would result in soil liquefaction. • vibration or noise needs to be minimized.g. • required support system needs to be in close pile proximity to existing structures. karstic areas. 10 . Typical Micropile Construction Sequence Using Casing 11 . Construction Type Classification 12 . TITAN Injection Bore Anchor System and Components 13 . 14 . 15 . the flushing grout will be replaced with a richer grout. After reaching the final depth. The hollow bars with a typical length of 3m are coupled and drilled to required depth. With the continuous Injection stage.CTS/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 the borehole and flushes the cuttings out of the hole. the pressure injection continuous. 45 3.Final Grout W/C 0.Typical cross section of an exhumed IBO® Micro-Pile 2 1 3 1.Flushing grout W/C 0.Hollow Bar 2.Ground improvement 16 4 .7 Soil Cement mix 4. 18 30 1.5 220 58.87 73 4.06 103 5.Hollow TITAN Bar Rod Size D out/D in mm 30/16 Load Capacity Nominal Steel Area Ultimate Yield Dia.2 730 218.2 2282 778.13 40/20 726 40/16 1.12 130 .5 220 58.53 73/53 1631 103/78 4.1 970 404.5 260 96.36 879 52/26 2.61 395 30/11 0.57 40 2.0 320 121.9 1160 513.88 3146 103/51 8.6 5250 mm 1.79 9540 kN 49.1 3460 1785.1 525 164.59 382 30/14 0.5 180 49.18 30 1.4 660 208.7 430 118.69 446 1.5 260 72.4 2750 1180.8 1800 618.2 539 148.53 5501 130/60 14.5 7940 kN 40.06 103 4.18 30 1.07 1337 2.9 929 260.05 52 2. 2 in kips kips in 2 mm 0.57 40 1. CTS/TITAN Hollow Bar System Drill Bit Hollow Titan Bar Centraliser Coupling Bearing Plate Hex Nut Pipe Sleeve 18 . Drill Bit Selection Clay Bit: Clay.T Dense Sand with Gravel and small Boulders > 50 S. Sandstone. strength < 70 MPa Dolomit.P. sand-mixed Ground without Boulders < 50 S. Shale. strength 70-150 MPa Reinforced Concrete or Rock. Phylit. Slate. strength > 70 MPa For controlled directional drilling (tolerance < 2% of the length) Cross Cut Bit: Button Bit: Carbide-Bit: Carbide Button Bit: Carbide Step Bit: 19 .T Weathered Rock. Granite.P. Drill Bit Selection Chart 20 . Full strength Couplers. to develop the ultimate strength of the bar 21 . Centralizers to allow for grout passage 22 . 2 nuts for tension/compression piles.Spherical hex nuts. (bearing plate with top and bottom nut) 23 . Double nut and plate connection to grade beam 24 . Corrosion Protection • Epoxy Coating • Metalizing • Sacrificial steel 25 . 4% Loss = 72.2% Loss = 72.6 kips • Aggressive Ground Aggression: 18.8 kips • Mild Ground Aggression: 11.7 kips • No Ground Aggression: 6.7 kips * 0.Sacrificial Steel Method TITAN 40/20 hollow bar over 60 years Allowable Design Load: 72.7 kips * 0.816 = 59.7 kips * 0.8% Loss = 72.888 = 64.3 kips 26 .932 = 67. Sacrificial Steel Method 27 . 2 x d 1.TITAN Hollow bar Micro Pile Grout cover min. 20 mm Natural Soil Stabilized and densified Soil Drill Bit Hollow Bar Soil/Cement mix d Drill Bit Diameter D > 2. slate 28 . Phylit.0 x d for medium to coarse gravel for sand und sandy gravel for cohesive soil (clay) for weathered sandstone.0 x d 1.5 x d 1. Micropile Design 29 . Micropile Design 30 . Micropile Design 31 . 32 . Micropile Structural Capacity . STRUCTURAL DESIGN OF MICROPILE UNCASED LENGTH From FHWA Design Guidelines 34 . 33 f = c Tension [ ' c−grout × Agrout) +(0.Structural Design of Uncased Pile (IBC) Compression P−allowable (0.4 Fy−bar × Abar) ] Pt − allowable = 0.6 Fy −bar × Abar 35 . Load Test Structural Capacity Pult−compression = (0.85 f [ ' c − grout × Agrout ) + ( f y−bar × Abar ) ] Pult −tension = f y −bar × Abar [ ] 36 . Micropile Geotechnical Capacity . 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 38 . Grout to Ground Adhesion Strength 39 . Ultimate Bond Stress for Rock to Grout as Recommended by PTI 40 . Ultimate Bond Stress for Cohesionless Soils to Grout as Recommended by PTI 41 . Ultimate Bond Stress for Cohesive Soils to Grout as Recommended by PTI 42 . Sample Micropile Design 43 . Bond Stress for TITAN Anchors as Recommended by ISCHEBECK 44 . Sample Micropile Design 2 2 45 . Sample Micropile Design 46 . 47 . 48 . tensile. similar to reinforcing steel in concrete. Hollow bars have a larger section modulus than solid bars. and lateral forces.Summary The hollow bar. is left in the ground as reinforcing steel to transmit compressive. With the continuous tremi-grout injection. 100% grout cover and therefore excellent corrosion protection is accomplished. 49 . used as both drill rod and grout conduit. Micropile Testing Procedures and Guidelines 50 . Micropile Load Tests There are four types of test loading: •compression test •uplift or tension test •lateral-load test •torsion-load test 51 . 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. 52 Schematic of Compression Load Test Arrangement (ASTM D1143/D1143M-07) 53 Schematic of Tension Load Test Arrangement (ASTM D3689) 54 Schematic of Lateral Load Test Arrangement (ASTM D3966) 55 Micropile Tension Test 56 . Micropile and Anchor Testing 57 . Exhumed TITAN Anchors 58 . TITAN Anchor Drilled Through Boulder 59 . 60 . 61 . 62 . 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 63 . Equipment For Grouting and Drilling 64 . VS 100 65 . Water gauge with holding tank . 000 PSI.45 minimum strength at 28 days = 3.0 Final Grout .Neat Water/Cement Grout Mix: Potable Water Cement Type I. II or III Drilling and Flushing . 67 .W/C = 0.7-1.W/C = 0. 68 . one for the thinner flushing grout and one for the final grout.Obermann VS-63 High speed high shear-colloidal mixer with two mixers. Water/cement dosing system and double plunger pump. The use of an automatic logging system for measurement. recording and documentation of grout volume and pressure is also recommended. 69 . Texas • 9 Regional US Chapters • Extensive membership list. significant annual operating budget with a farreaching agenda • Representing the Drilled Shaft. – headquartered in Dallas.The ADSC • International Scope. 70 . Anchored Earth Retention and Micropile construction technologies. OSHA. DOTs. construction and inspection seminars.) 71 .Work of the ADSC includes – Establishing standards & specifications for the industries it serves – Promoting ethical practice – Conducting design. worldwide – Developing technical materials – Funding and conducting research – Providing a forum for technology transfer – Stimulating industry growth – Interfacing with corresponding industries and agencies (FHWA. etc. Available thru the ADSC • Network of Experienced and Proven Contractors. – Videos and other media – Design. Personnel Training Materials • Technical Resources – – – – – On-Line Technical Library Technical Papers Design Manuals Foundation Drilling Magazine Specifications 72 . Safety. Design Professionals and Material Suppliers! • Training Opportunities – Regional seminars. 2005. FHWA NHI-05-039 Standard industry reference with detailed examples of micropile design and applications 73 .References Micropile Design and Construction Reference Manual. 2006 FHWA Review and Assessment of Hollow Core Soil Nails for Transportation Projects 74 .Soil Nail Design and Construction State-ofthe-Practice. April. ADSC-IAF Document Buckling of Micropiles Provides guidelines for Buckling calculations of micropiles 75 . Phoenix. (2004).PTI. Recommendations for prestressed rock and soil anchors. PostTensioning Institute. AZ. 76 . A History of Micropiles and Early Applications from the Inventor 77 . dot.com 78 .gov/engineering/geotech /library_listing.fhwa.dfi.cfm • http://www.adsc-iafd.org/ • http://www.Web Resources • http://www. Questions Comments Observations 79 . Thank You for Your Attention 80 .