Standard Guidelines For The Design and Installation of Pile Foundations ASCE - 1997 [PDF]

Zitiervorschau

ASCE 20-96

American Society of Civil Engineers

Standard Guidelines for the Design and Installation of Pile Foundations

Published by American Society of Civil Engineers

1801 Alexander Bell Drive Reston, Virginia 20191-4400

Abstract: This Standard provides a guideline for an engineering approach to the design and subsequent installation of pile foundations. The purpose is to furnish a rational basis for this process, taking into account published model building codes and general standards of practice. It covers such topics as: 1) Administrative requirements; 2) pile shaft strength requirements; 3) soil-pile interface strength requirements and capacity; 4) design loads; 5) design stresses; 6) construction and layout guidelines for pile design; and 7) installation guidelines for pile construction. In addition, the Standard includes information on applicable standards from ASTM, AWPA, and ACL It concludes with an Appendix on partial factors of safety. Library of Congress Cataloging-in-Publication Data American Society of Civil Engineers. Standard guidelines for the design and installation of pile foundations / ASCE, American Society of Civil Engineers. p. cm. ISBN 0-7844-0219-1 1. Piling (Civil engineering)~Design and construction—Standards. I. Title. TA780.A523 1997 96-30072 624.1'54-dc21 CIP Photocopies. Authorization to photocopy material for internal or personal use under circumstances not falling within the fair use provisions of the Copyright Act is granted by ASCE to libraries and other users registered with the Copyright Clearance Center (CCC) Transactional Reporting Service, provided that the base fee of $4.00 per article plus $.50 per page is paid directly to CCC, 222 Rosewood, Drive, Danvers, MA 01923. The identification for ASCE Books is 0-7844-0219-l/97/$4.00 + $.50 per page. Requests for special permission or bulk copying should be addressed to Permissions & Copyright Dept, ASCE. Copyright © 1997 by the American Society of Civil Engineers, All Rights Reserved. Library of Congress Catalog Card No: 96-30072 ISBN 0-7844-0219-1 Manufactured in the United States of America.

STANDARDS In April 1980, the Board of Direction approved ASCE Rules for Standards Committees to govern the writing and maintenance of standards developed by the Society. All such standards are developed by a consensus standards process managed by the Management Goup F (MGF), Codes and Standards. The consensus process includes balloting by the balanced standards committee made up of Society members and non-members, balloting by the membership of ASCE as a whole and balloting by the public. All standards are updated or reaffirmed by the same process at intervals not exceeding five years.

The following standards have been issued: ANSI/ASCE 1-82 N-725 Guidelines for Design and Analysis of Nuclear Safety Related Earth Structures ANSI/ASCE 2-91 Measurement of Oxygen Transfer in Clean Water ANSI/ASCE 3-91 Standard for the Structural Design of Composite Slabs and ANSE/ASCE 991 Standard Practice for the Construction and Inspection of Composite Slabs ASCE 4-86 Seismic Analysis of Safety-Related Nuclear Structures Building Code Requirements for Masonry Structures (ACI530-95/ASCE5-95/TMS402-95) and

Specifications for Masonry Structures (ACI530.195/ASCE6-95/TMS602-95) Specifications for Masonry Structures (ACI53095/ASCE6-95/TMS602-95) ANSI/ASCE 7-95 Minimum Design Loads for Building and Other Structures ANSI/ASCE 8-90 Standard Specification for the Design of Cold-Formed Stainless Steel Structural Members ANSI/ASCE 9-91 listed with ASCE 3-91 ANSI/ASCE 10-90 Design of Latticed Steel Transmission Structures ANSI/ASCE 11-90 Guideline for Structural Condition Assessment of Existing Buildings ANSI/ASCE 12-91 Guideline for the Design of Urban Subsurface Drainage ASCE 13-93 Standard Guidelines for Installation of Urban Subsurface Drainage ASCE 14-93 Standard Guidelines for Operation and Maintenance of Urban Subsurface Drainage ANSI/ASCE 15-93 Standard Practice for Direct Design of Buried Precast Concrete Pipe Using Standard Installations (SIDD) ASCE 16-95 Standard for Load and Resistance Factor Design (LRFD) of Engineered Wood Construction ASCE 20-96 Standard Guidelines for the Design and Installation of Pile Foundations ASCE 21-96 Automated People Mover Standards-Part 1

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FOREWORD Piles differ from most other portions of a structure in that with few exceptions they are not able to be visually inspected after installation. Driven piles are generally subjected to considerable stress during installation. For both driven and drilled piles, the potential for the pile shaft to sustain damage during installation should be considered in the determination of minimum dimensions and maximum design stresses. Furthermore, consistently identifiable soil strength parameters, coupled with consistent or uniform bearing strata are generally not luxuries found in foundation design. This Standard provides a guideline for an engineering approach to the design and subsequent installation of pile foundations. The purpose is to provide a rational basis for this process, taking into

account published model building codes and general standards of practice. It is intended for use by professional personnel of sufficient competency to evaluate the essence and limitations of the provisions contained herein and who will accept the responsibility for the application of the material presented. In general, the expertise required to properly implement this Standard is seldom found in one individual. A common design team includes both a structural engineer and a geotechnical engineer, and may in addition include a pile contractor to provide construction expertise and cost estimates. Communication among all members of the design team and the client will aid in the successful implementation of this Standard.

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ACKNOWLEDGMENTS The American Society of Civil Engineers (ASCE) acknowledges the work of the Pile Foundations Standards Committee of the Codes and Standards Activities Committee (CSAC). This group comprises individuals from many backgrounds including: consulting engineering, research, the construction industry, design, and private practice. These Standard Guidelines were prepared through the consensus standards process by balloting in compliance with procedures of ASCE's Codes and Standards Activities Committee (CSAC). Those individuals who serve on the Standards Committee are: Carroll L. Crowther, Chairman Girish Agrawal James E. Barris James C. Benton, Jr. Edward Demsky

Thomas D. Dismuke Michael F. Engestrom C. Scott Fletcher Frank Gaasch James S. Graham Ahmad Habibian Joseph C. Harden Steven W. Hunt Mohamad H. Hussein Barry A. Johnson Michael L. Jones Jai Kim Robert G. Lukas Daniel M. McGee Cetin A. Okcuoglu Robert F. Pierry, Jr. Abdulreza A. Sadjadi Jerry A. Steding Yuanhui Sun

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Standard Guidelines for the Design and Installation of Pile Foundations Contents FOREWORD STANDARDS ACKNOWLEDGMENTS

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GENERAL 1.1 Scope 1.2 Referenced Standards 1.3 Deviations from This Standard 1.4 Engineer Required 1.5 Definitions

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ADMINISTRATIVE REQUIREMENTS 2.1 Investigation for Design 2.2 Design Analysis 2.3 Durability 2.4 Adjacent Property 2.5 Use of Existing Piles 2.6 Special Design Considerations 2.7 Coordination with Other Work 2.8 Installation Criteria 2.9 Plans and Specifications 2.10 Records 2.11 Design Modifications 2.12 Load Tests

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PILE SHAFT STRENGTH REQUIREMENTS 3.1 General 3.1.1 Minimum pile shaft material requirements 3.2 Structural Strength of Piles 3.2.1 Maximum allowable shaft stresses 3.3 Critical Shaft Section 3.4 Handling and Driving Stresses 3.5 Piles with Unsupported Length

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SOIL-PILE INTERFACE STRENGTH REQUIREMENTS AND CAPACITY 4.1 General 4.1.1 Analysis of soil-pile capacity 4.2 Designation of Supporting Strata 4.2.1 Ultimate capacity 4.2.2 Pile groups 4.3 Static Resistance Analysis 4.3.1 Pile movement under load 4.4 Negative Friction 4.5 Pile Load Tests 4.5.1 Design capacity by load tests 4.5.2 Dynamic testing 4.5.3 Static load tests 4.5.3.1 Static compressive load tests 4.5.3.2 Static tensile load tests

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STANDARD GUIDELINES FOR THE DESIGN AND INSTALLATION OF PILE FOUNDATIONS

4.5.3.3 4.5.3.4 4.5.3.5

Static lateral load tests Time of load tests Interpretation of static pile load tests

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DESIGN LOADS 5.1 Loads To Be Used 5.2 Maximum Combination of Loads 5.3 Pile Groups

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DESIGN STRESSES 6.1 General 6.1.1 Use of higher allowable stresses 6.2 Timber Piles 6.2.1 Dimensions and stresses 6.2.2 Preservative treatment 6.2.3 Untreated timber piles 6.3 Concrete Piles 6.3.1 Reinforced precast concrete piles 6.3.2 Prestressed precast concrete piles 6.3.3 Concrete-filled shell piles 6.3.4 Uncased cast-in-place and augered pressure grouted concrete piles 6.3.5 Enlarged base piles 6.4 Steel Piles 6.4.1 Allowable stresses 6.4.2 Minimum dimensions, rolled steel H piles, and fabricated piles 6.4.3 Minimum dimensions, steel pipe piles 6.4.4 Steel pipe or tube piles—concrete filled 6.4.5 Mandrel-driven shell or tube piles 6.4.6 Driven caisson-type piles 6.4.7 Composite and other pile types 6.5 Mini-Piles 6.5.1 Mini-pile strength requirements and capacity 6.5.2 Mini-pile quality control

9 9 9 9 9 9 9 9 9 9 10 10 10 10 10 10 11 11 11 11 11 12 12 12

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CONSTRUCTION AND LAYOUT GUIDELINES FOR PILE DESIGN 7.1 General 7.2 Deviation 7.3 Driving Stresses 7.4 Location and Axial Alignment Tolerances 7.5 Obstructions and Hard Strata 7.6 Design Modifications Due to Field Conditions 7.7 Cross-Sectional Area 7.8 Pile Spacing 7.9 Caps and Bracing 7.10 Splices 7.11 Multiple Pile Types, Capacities, or Methods of Installation

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INSTALLATION GUIDELINES FOR PILE CONSTRUCTION 8.1 General 8.2 Installation Equipment 8.2.1 Selection of driving system 8.2.2 Followers 8.3 Equipment for Augered Pressure Grouted Piles 8.3.1 Augering equipment

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STANDARD GUIDELINES FOR THE DESIGN AND INSTALLATION OF PILE FOUNDATIONS

8.4 8.5 8.6 8.7 8.8 8.9 8.10 8.11 8.12 8.13 8.14 8.15 8.16 8.17 9

8.3.2 Mixing and pumping equipment Operations Continuous Driving Pre-Excavation Heaved Piles Installation Sequence Cast-in-Place Concrete Driving and Installation Anomalies Relaxation Soil Freeze or Setup Obstructions Pile Protection Bent, Dog-Legged, or Collapsed Piles Pile Installation and Testing Records Probe Piles

APPLICABLE STANDARDS 9.1 ASTM Standards 9.2 AWPA Standards 9.3 ACI Standards

APPENDIX A PARTIAL FACTORS OF SAFETY A.I Introduction A.2 Application A.3 Commentary on Appendix A A.3.1 Factor F, A.3.2 Factor F,

INDEX

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CHAPTER 1

General

which they are used. Webster's New International Dictionary of English Language, Unabridged, latest edition, shall be considered as providing ordinarily accepted meanings. Acceptable or Accepted: Meets with the approval of the Engineer or Geotechnical Engineer. Documentation of such approval usually constitutes acceptance or approval.

1.1 Scope The provisions of this Standard establish guidelines for the design and construction of pile foundations. Many of the design considerations contained herein require a working knowledge of soil mechanics and foundation engineering. Such knowledge is necessary for the design part of this Standard.

1.2 Referenced Standards In addition to local codes and ordinances having jurisdiction, the provisions of the Referenced Standards, Sec. 9 of this Standard should be considered where they apply and where noted.

1.3 Deviations from This Standard Deviations from the requirements of this Standard Guideline should be permitted only under the conditions stated in Sec. 6.1.1 and 6.4.7. Use of proprietary, new and/or improved pile types, materials, evaluation techniques, and pile installation techniques are not prohibited, as long as the design and installation of the piles are shown to comply with these guidelines.

1.4 Engineer Required All work covered by this Standard should be under the direction of a professional engineer (1) having current experience and qualifications in pile foundation design, construction, and understanding verification techniques as dictated by the project requirements, and (2) having a valid professional engineering license in the locality where the piles are to be installed. This professional engineer is hereinafter referred to as the Engineer. The Engineer may delegate portions of the exploration, design, testing, and inspection to qualified personnel, working under his or her direction, where permitted by local law.

1.5 Definitions The following terms are defined with reference to the work covered by this Standard. Terms in the Standard that are not defined shall have their ordinarily accepted meanings within the context with

Accepted (Engineering) Practice: The practice of Civil Engineering that conforms to principles, tests, and standards of care and skill ordinarily applied by qualified civil engineering professionals. Augered Pressure Grouted Pile (APGP): A castin-place concrete pile made by rotating a continuous-flight, hollow shaft auger into the ground to a specific depth, or until other specified criteria are reached. Grout is then injected through the auger shaft in such a way as to exert pressure on the soil surrounding the augered hole as the auger is withdrawn. Building Official: The official or his or her duly authorized representative or other designated authority charged with the administration and enforcement of the building code. Cast-in-Place: Concrete placed into a pile shaft at the site during, or after, installation of the pile. Capacity (Ultimate Load): The load at which the pile failure first occurs due to exceeding the structural strength of the shaft, or the ultimate resistance of the supporting materials. Critical Section: The cross-section of a pile shaft where the maximum stresses occur. Cut-off Elevation: The elevation at the top of pile (also called the head or butt) as shown in plans and specifications. Current Experience: Experience within the last five years utilizing design, testing, and installation techniques applicable to the current project. Design Load: The maximum compressive, tensile, or lateral load, or combination thereof, considered to act on the pile during the life of the structure. Design Stress: The stress imposed on the pile cross-section by the design load and calculated in accordance with accepted engineering practice. Drive Head (Drive Cap, Anvil, or Helmet): A steel casting or forging generally shaped to fit the piledriving hammer base to the pile, so as to uniformly distribute the hammer blows to the top of the pile.

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STANDARD GUIDELINES FOR THE DESIGN AND INSTALLATION OF PILE FOUNDATIONS

Dynamic Analysis: The application of pile-driving energy formulae or wave equation solutions in the determination of driving stresses and/or pile capacity. Dynamic Measurement and Analysis: A method of testing and analysis that involves measurement of the dynamic response of a pile under dynamic impacts (during driving or re-strike) and the subsequent data analysis based on one-dimensional elastic wave propagation principles. High strain dynamic testing is performed under the impacts of conventional pile-driving hammers or other similar devices, and low strain dynamic testing is performed with small hand-held hammers. Engineer: The duly registered engineer directly responsible for the design of the pile foundations. (See Sec. 1.4.) Established Methods of Analysis: See Accepted Practice. Failure: (1) Breaking or excessive yielding of the material comprising the pile. (2) Progressive movement in response to a sustained load. (3) Movement of a pile beyond an established acceptable limit deemed appropriate by the Engineer. Failure Load: That load which produces one of the modes of failure as defined previously. Freeze: (or Pile Setup) The increase in carrying capacity of a pile after driving or during interruptions in driving due to soil pore pressure changes, soil strength gain after remolding, stress redistributions, and other factors. Follower: A temporary extension, used during driving, that permits the driving of the pile top below ground surface, water surface, or below the lowest point to which the pile hammer can reach without disengagement from the leads. Geotechnical Engineer: A duly registered professional civil engineer with experience and training in soil mechanics and earth sciences. Hammer Cushion (Block): A device or material inserted between the hammer ram and a drive head or base plate to protect the hammer and drive head or cap from destructive direct impact. The hammer cushion contains cushioning material having sufficient stiffness to transmit hammer energy effectively to the pile.

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Mini-Pile: A pile of small cross-sectional dimensions. For this Standard, mini-pile shall refer to any pile with cross-sectional dimensions less than the minimums specified under the individual pile types covered in Sec. 6.2, 6.3, and 6.4. Negative Friction: Load imposed on the pile by the surrounding soil as it tends to move downward relative to the pile shaft due to soil consolidation, surcharges, or other causes; also called down-drag load. Pile Cushion: Material, most commonly plywood, placed on top of a precast concrete pile to control compressive and tensile stresses in the pile during driving; to distribute the force of the hammer blow uniformly over the top of the pile; and to compensate for surface irregularities at the top surface of the pile. Static Analysis: Analysis of the supporting capacity of the pile-soil system employing relevant soil and/or rock strength parameters and properties along with established interaction correlations between the pile shaft and the soil/rock materials. Service Load (Design Load): The maximum compressive, tensile, or lateral load, or combination thereof, considered to act on the pile during the life of the structure. Settlement (Load Test): Gross settlement is the total downward movement of a pile that occurs under an applied test load. Net settlement is gross settlement minus the rebound that occurs after removal of the applied test load. Supporting Materials: The layer or layers of soil or rock that provide principal support to the pile. Ultimate Load (Capacity): The load at which the pile failure first occurs due to exceeding the structural strength of the shaft, or the ultimate resistance of the supporting materials. Wave Equation Analysis: A rational computerbased method of analysis of the interaction of the hammer, pile, and soil, based on one-dimensional elastic wave propagation principles. Working Load (Design Load): The maximum compressive, tensile, or lateral load, or combination thereof, considered to act on the pile during the life of the structure.

STANDARD GUIDELINES FOR THE DESIGN AND INSTALLATION OF PILE FOUNDATIONS

CHAPTER 2

Administrative Requirements

2.1 Investigation for Design A foundation investigation and engineering analysis of the site and subsurface conditions should be conducted, under the supervision of a Geotechnical Engineer, to provide the basis for the design and installation of foundation piles. Borings, test pits, cone probes, subsurface sampling, field and laboratory tests, or in the sole judgement of the Engineer, other data including information from adjacent sites, previous construction or engineering, and other sources of site information may be used to identify appropriate geotechnical design criteria, or to confirm design and installation criteria previously obtained. All such information should be identified and maintained in the project files. 2.2 Design Analysis The results of the subsurface investigation and/or other available data should then be used by the Engineer to prepare the pile foundation design analysis. The design analysis should include consideration of the loading conditions, environment, structure deformation tolerances, anticipated bearing strata, acceptable methods of pile installation, suitable pile types, and the character and performance of previous or existing construction at the site or adjacent sites. The Engineer should then prepare a design for the pile foundation with appropriate margins of safety against (1) failure of the earth materials, and (2) against over-stressing of the pile shaft as required by this Standard. The foundation design should be consistent with the deformation tolerances of the structure. The pile type, design load, pile capacity, estimated pile lengths, and installation criteria are integral parts of the foundation design. 2.3 Durability Piles may deteriorate due to biological, chemical, and physical actions caused by particular site conditions. Therefore the Engineer should evaluate possible deleterious actions on pile materials that limit the life of the pile or reduce its structural capacity.

The pile design should show a reasonable expectation of the shaft structural strength required by this Standard for the expected life of the supported structure, or provisions should be made for pile protection, or for any subsequent replacement that may be required. For piles that extend above the ground surface or through open water, special consideration should be given to the possible effect of environmental conditions on the pile material. Appropriate measures should be taken to safeguard the foundation from deterioration due to conditions such as atmospheric corrosion, sea water exposure, thermal stresses, and freeze-thaw cycles. 2.4 Adjacent Property The Engineer should evaluate the effects of pile installation on existing underground structures, including utilities, and excavations, and on adjacent structures and property, and, as necessary, should incorporate suitable protective requirements in the project contract documents. 2.5 Use of Existing Piles Existing piles may be used to support new construction provided that, prior to the new construction, the Engineer determines that there is satisfactory evidence that the piles are sound and will support the intended loads. Such evidence should include one or more of the following. (1) Documentation of the loading and concurrent satisfactory performance of the previous foundation; (2) representative load testing; (3) pile re-driving; (4) dynamic measurement and analysis; (5) static analysis; (6) a subsurface investigation to identify representative conditions that provide support to the piles; and (7) other information, exploration, and testing as dictated by project requirements. 2.6 Special Design Considerations Piles should be designed and installed to allow for exposure, appropriate unsupported length, scour, and lateral loading, without unacceptably reducing the load-carrying capacity or lateral stability of the piles. 2.7 Coordination with Other Work The design should take into account coordination between pile installation operations and other site operations, including but not limited to, excava3

STANDARD GUIDELINES FOR THE DESIGN AND INSTALLATION OF PILE FOUNDATIONS

tions, shoring and bracing, dewatering, slope stability, underpinning, and any other pertinent operations. If specific procedures and orders of operations are required, these should be specified in the design. 2.8 Installation Criteria The Engineer should document the design criteria and driving or installation criteria to be applied to the project or to each pile or pile group. The final installation criteria, as modified by any tests, probe pile installation, field conditions, or any other reasons should be documented. These installation criteria should include minimum hammer energies, driving resistances, minimum auger torques and energies, minimum rates of pumping, maximum rates of auger withdrawal, penetration rates, penetration lengths, minimum tip elevations, combinations of these criteria, or other specific equipment, material, or procedural requirements. 2.9 Plans and Specifications In addition to any other specific building code required submittals, the plans and specifications should show, or include, the following: (1) Location of each pile, relative to permanent reference. (2) Unique designation or number for each pile. (3) Pile cut-off elevation. (4) Minimum pile tip elevation for each area of generally similar soil conditions, if appropriate. (5) Required inclination and direction of inclination. (6) Required orientation of nonround piles, if applicable. Note: It is not normally considered good practice to attempt to restrain the pile so as to prevent rotation or other movements that may occur during installation due to underground conditions. (7) Pile design loads and factors of safety. (8) Logs, location, and elevations of soil borings relative to the pile location reference system. (9) Pile testing and inspection requirements. (10) Pile installation criteria. (11) Pile reinforcing, and any attachment or anchor details. 2.10 Records The installation and construction of pile foundations should be observed and documented by the 4

Engineer, or a representative designated by the Engineer. Records should confirm that the final pile installation criteria, including any modifications, are in accordance with Sec. 8.16 of this Standard. These observations and documentation should include complete information on any pile testing, equipment, and installation operations. The Engineer should retain copies of installation records as long as legally required, but no less than one year after essential completion of the structure. 2.11 Design Modifications Design modifications caused by changed or unanticipated field conditions should be documented by the Engineer, and such modifications should meet the applicable design requirements of this Standard. 2.12 Load Tests If load tests are performed or required, tests should be in accordance with Sec. 4.5 of this Standard. The Engineer or his or her representative should specify, observe, and document details of each pile load test.

CHAPTER 3

Pile Shaft Strength Requirements

3.1 General Pile design involves separate strength requirements: (1) the strength of the pile shaft, and (2) the strength of the earth materials at the soil-pile interface along the pile shaft as well as at, and below, the pile tip (Sec. 4.0). 3.1.1 Minimum pile shaft material requirements. Unless otherwise specified, the minimum pile shaft strength provisions detailed in this section (Sec. 3.0) should apply. 3.2 Structural Strength of Piles The overall structural stresses under the design load occurring in the installed pile shaft should be

STANDARD GUIDELINES FOR THE DESIGN AND INSTALLATION OF PILE FOUNDATIONS

equal to or less than those allowed by local codes or this Standard. The design loads should include axial compression or tension, combined with moment or shear. In determining the necessary structural strength of a pile, consideration should be given to material strength reductions that may occur as a result of the variability of material properties, accidental eccentricity of the applied load, pile mislocation, and deviation of the installed pile cross-section from the shape and dimension specified. The effect of lateral loads, not resisted by inclined piles or other structural elements, should be evaluated during pile design. The Engineer should design the pile based upon a determination of the lateral deflection of the pile head and distribution of resulting moment and shear along the pile shaft, using a method of analysis that takes into account pile-soil elastic interaction, load duration, load repetition, structural restraint at the pile head, and the effect of group action. 3.2.1 Maximum allowable shaft stresses. Provisions for maximum allowable stresses at design loads are provided by material and pile type in Sec. 6.0. 3.3 Critical Shaft Section The Engineer should analyze the distribution of loads along the pile shaft and design for sufficient strength at all locations. Determination of the critical section is essential for tapered or other nonuniform piles. 3.4 Handling and Driving Stresses Piles should be designed to be of sufficient size and strength so that detrimental yielding, cracking, or failure of the pile does not occur during transportation, lifting, or driving. The design should consider: (1) the maximum stresses induced during handling and driving, (2) the pile lengths that may be required, and (3) the compatibility of the driving equipment and pile material, with the soil/rock subsurface conditions. 3.5 Piles with Unsupported Length Piles or portions thereof located in air, water, or soil not providing lateral support, should be designed in accordance with accepted engineering practice for both unsupported column and exposure conditions.

CHAPTER 4

Soil-Pile Interface Strength Requirements and Capacity

4.1 General Pile design involves separate strength requirements: (1) the strength of the pile shaft, (Sec. 3.0), and (2) the strength of the earth materials at the soil-pile interface along the pile shaft as well as at, and below, the pile tip (Sec. 4.0). 4.1.1 Analysis of soil-pile capacity. Evaluation of the capacity of a single pile should be performed using load tests, static analyses, dynamic testing and analyses, or preferably a combination thereof. Documented correlations developed from on-site tests and driving resistance or other installation procedures, using the same hammer assemblies or auger equipment and pump combinations, or from documented experience applicable to the installation equipment, site conditions, and the pile load anticipated, may be used in conjunction with Sec. 4.3. 4.2 Designation of Supporting Strata The Engineer should designate the stratum or strata into which piles are designed to be installed. Some overlying strata may produce negative friction loads, or may cause difficult installation, or otherwise obstruct installation. If any strata are not acceptable to the Engineer as the bearing stratum or strata, they should be so identified. 4.2.1 Ultimate capacity. Individual piles, each pile in a pile group, and each group of piles as a unit, should develop, in the designated strata, an ultimate earth material resistance or capacity, in accordance with Appendix A of this Standard. The frictional or cohesive shear resistance in overlying nonload-bearing strata should be disregarded in this analysis. Potential negative frictional or cohesive shear loads should be considered in the pile design. No strata underlying the bearing strata should cause the ultimate capacity of a pile or pile group to be less than that permitted by Appendix A of this Standard or as determined by an acceptable method of analysis or verification. 4.2.2 Pile groups. Where possible, pile spacing should be such that the capacity of the pile group 5

STANDARD GUIDELINES FOR THE DESIGN AND INSTALLATION OF PILE FOUNDATIONS

need not be reduced to less than the sum of the individual pile capacities. Pile spacing should take into account the possibility of piles interfering with one another as pile length increases. (See also Sec. 5.3.) 4.3 Static Resistance Analysis Regardless of other methods used to supplement the determination of pile capacity, a static resistance analysis should be conducted. Determination of the pile-soil capacity by such engineering analysis requires soil strength properties to be known, or reliably estimated. Such properties are obtained from experience with similar soil profiles, correlation with field tests, or laboratory tests. The analysis should also consider pile installation methods, the effect of pile group action, the interface surface of the pile with the soil, the potential for water table fluctuations, seismic activity, wave action, cyclic action, scour, dewatering, surcharge, excavation, strength regain or relaxation, and effects of displacement piles. Static resistance analysis should be in accordance with accepted engineering principles and utilize appropriate soil or material strength parameters. The analysis calculates the frictional or adhesional resistance along the pile shaft in each appropriate layer, and for compressive piles, adds to it the end-bearing capacity of the pile tip. The potential for consolidation of the supporting strata, causing settlement of the pile or the potential of overstressing strata below the pile tips should be considered in the static resistance analysis. Lateral capacity analysis for piles subjected to lateral loads should be made. Soil or earth material property data used in the analysis should be derived from tests on representative samples of the strata resisting lateral deformation, or full-scale load tests, or from recognized data published for similar materials. The deformation and capacity analysis should take into account the pile-soil interaction. 4.3.1 Pile movement under load. The static analysis should consider the potential vertical and horizontal deformations of individual piles or groups of piles under the design loads. An accepted method of analysis should be used. If the deformations predicted could potentially cause unacceptable or harmful distortion, or instability of the supported structure, the foundation should be redesigned to preclude such deformations. 4.4 Negative Friction Applicable methods of subsurface exploration, testing, and static analysis should be employed to 6

detect strata that may subside, or may be consolidated during the life of the structure, leading to negative friction loading on the piles. Such negative friction loads should be accounted for in the pile design, or methods should be employed that reduce or prevent the transmission of such loads to the pile shaft. 4.5 Pile Load Tests 4.5.1 Design capacity by load tests. The compressive, tensile, and lateral design capacity of individual piles may be determined or verified by static load tests. Dynamic tests may be used to estimate pile capacity, driving stresses, and shaft integrity. Static pile load testing should be required in all situations determined by the Engineer to be unreliable in determining design capacity, installed capacity, or other uncertain conditions. Dynamic measurement and analysis can be used if the Engineer has confidence in its effectiveness under the specific project conditions. Engineers are encouraged to specify static axial load tests to failure, or as a minimum to a limitation of 300 percent of estimated design load. Testing piles to failure provides valuable information that can allow a design based on measured pile-soil interactions. Pile lengths can often be shortened as a result of such testing. 4.5.2 Dynamic testing. Dynamic testing and analysis should incorporate pile dynamic measurements under impacts during pile driving or re-striking and should be based on one-dimensional elastic stress wave propagation principles. Such test methods provide measurements and data that may be used to evaluate pile capacity, hammer/driving system performance, pile shaft structural integrity, static pile capacity, and driving stresses. This type of testing is called a high strain dynamic test. Any such dynamic testing should be conducted in accordance with ASTM D4945, and the specific requirements of the project. Low strain pile dynamic testing is performed for evaluation of pile structural integrity. This type of testing generally consists of measuring the dynamic response of the pile top under impacts of a small hand-held hammer and subsequent data acquisition and analysis based on one-dimensional stress wave propagation principles. Dynamic analysis tests should not be the sole means of estimating the capacity of pile foundations and, at a minimum, should be accompanied by a static design analysis based on appropriate earth material strength parameters. (See Sec. 4.5.1 concerning the use of static load testing.)

STANDARD GUIDELINES FOR THE DESIGN AND INSTALLATION OF PILE FOUNDATIONS

4.5.3 Static load tests. 4.5.3.1 Static compressive load tests. When the capacity of individual piles is to be determined or verified by compression load testing, such testing should be in general accordance with ASTM D1143, and the specific requirements of the project. The requirements of the test program should be specified by the Engineer. These requirements should include the number of pile tests, specific test procedures, maximum test load if not carried to failure, and allowable deflection and/or acceptance criteria of a successful test pile, both under test load and after removal of load (re-bound). Interpretation of the load test results should be done under the direction of the Engineer. Determination of the design load should take into account allowable structural movement, and should be determined in accordance with recognized engineering principles. 4.5.3.2 Static tensile load tests. When the uplift capacity of individual piles is to be determined or verified by uplift load testing, such testing should be in general accordance with ASTM D3689 and the specific requirements of the project. The minimum requirements of the test program should be specified by the Engineer, including number of pile tests, specific test procedures, maximum test load if not carried to failure, and allowable deflection and/or acceptance criteria of a successful test pile, both under test load and after removal of load (re-bound). Interpretation of the load test results should be done under the direction of the Engineer. Determination of the design load should take into account allowable structural movement, and should be determined in accordance with recognized engineering principles. 4.5.3.3 Static lateral load tests. When the lateral capacity of individual piles is to be determined or verified by horizontal load testing, such testing should be in general accordance with ASTM D3966, and the specific requirements of the project. The minimum requirements of the test program should be specified by the Engineer, including number of pile tests, specific test procedures, maximum test load if not carried to failure, and allowable deflection and/or acceptance criteria of a successful test pile, both under test load and after removal of load (re-bound). Tests performed on a single pile should be analyzed to consider the effects of pile head restraint, concurrent axial loads on the pile, and pile group behavior. Interpretation of the load test results should be done under the direction of the Engineer.

Determination of the design load should take into account allowable structural movement, and should be determined in accordance with recognized engineering principles. 4.5.3.4 Time of load tests. Pile installation causes changes in the original conditions of the surrounding soils. The degree of disturbance caused depends mainly on the soil type, pile type, pile spacing, and method of installation. Static or dynamic load tests identify the pile capacity at the time of testing. Many factors should be considered in determining the amount of waiting time required, between pile installation and testing, for evaluation of "long term" pile capacity. This required waiting period should be determined by the Geotechnical Engineer from consideration of the time-dependent pile-soil strength characteristics, as well as construction scheduling constraints. Depending on soil types, waiting periods may range from minutes for piles bearing on rock and in some cohesionless soils to weeks for some cohesive soils. A minimum period of 24 hours between installation and testing is recommended. The relationship between pile capacity and time of testing can be established by several tests over a period of time. The number of static tests necessary can be reduced by utilizing dynamic tests. Static tests should be used to calibrate the dynamic tests. For cast-in-place piles, the time required for the concrete to reach sufficient strength must also be considered. 4.5.3.5 Interpretation of static pile load tests. Interpretation of load test results should be done under the direction of the Engineer. Determination of the design load should take into account allowable structural movement, and should be determined in accordance with recognized engineering principles. For piles tested in compression without failure occurring as defined in Sec. 1.5, the Engineer should attempt to determine the failure load of the pile. One approach in determining the failure load for the pile, if a quick load test is performed, is that the failure load can be the load corresponding to a measured movement of the pile top, in inches, equal to the sum of (1) the gross elastic compression (inches), plus (2) 1 percent of the equivalent pile diameter in inches, plus (3) 0.15 inches. Gross elastic compression is calculated assuming that the load at the pile top is transmitted fully to the pile tip. A quick load test is performed by applying equal load increments (10-15% of estimated design load) to the pile at intervals of 30 minutes or less. The modulus of the pile material is preferably determined by test. Alternatively, the moduli for timber, concrete, 7

STANDARD GUIDELINES FOR THE DESIGN AND INSTALLATION OF PILE FOUNDATIONS

or steel piles may be assumed from recognized standards. Where tip movement is measured, the failure load may be defined as the load corresponding to a pile tip movement of 0.15 inches plus one percent of the tip diameter. The foregoing interpretation applies to compression tests in which the load increments are held for not longer than one half hour. For tests in which test loads are held for longer than one half hour, the settlement at the end of one half hour at each increment, including a load of twice the design load, shall be used to determine the failure load as defined in this section. For piles tested with lateral load, the allowable lateral load should not be greater than 1/3 of the failure load. The design load should not produce a gross deflection at the pile top in excess of the lateral deflection specified by the Engineer and/or acceptance criteria. Where appropriate, the single pile test results should be adjusted by accepted relationships to account for pile group response and pile head restraint. Where uplift capacity is a design consideration, load testing should be conducted as appropriate. For piles tested under uplift or tensile loads, the allowable design load should not be greater than 50 percent of the failure uplift load, or 50 percent of that load which produces a deflection deemed appropriate by the Engineer. Under some conditions, the uplift design load for a single pile may be assumed to be 33 percent of the ultimate frictional load capacity determined by compression testing of a comparable pile, instrumented in order to define the load carried by shaft friction.

CHAPTER 5

Design Loads

5.1 Loads To Be Used The loads contributing to pile design loads consist of the service dead and live loads, including live load reductions, and other loads. When applicable, the loading provisions from current, legally adopted 8

Building Codes or ASCE 7- 95 should be used. To these service loads, the following loads should be added as applicable. (a) (b) (c) (d) (e)

(f) (g) (h) (i) (j)

Hydrostatic uplift; negative friction; dead load of piles and pile caps; fill or other overburden or surcharge loads acting on the foundation; lateral loads resulting from wind, earth pressure, water pressure, wave action, ice, or seismic action; uplift loads from swelling or expanding soils; impact; seismic loads; loads due to eccentricity; any other pertinent loads.

5.2 Maximum Combination of Loads. The Engineer should consider all loads acting on the piles and should investigate the combination of loads that can act concurrently in producing maximum loads. When extreme wind, wave, or earthquake loads are considered, an increase in design stress is permissible for allowable stress design only. No such increase should be permitted for structures whose design is controlled by wind, seismic, or wave forces acting alone or in combination with dead load. 5.3 Pile Groups. With respect to compressive loads, it is not necessary to consider group efficiency except for a group of friction piles in cohesive soils or where the pile spacing is less than 3 times the pile diameter in granular soils. In cohesive soils, the design load on a group of friction piles should not exceed 50 percent of the ultimate load capacity determined by a (block) analysis summing the ultimate bearing capacity of the soils within the plan area of the group and the ultimate shearing resistance on the peripheral surface inscribing the group. However, the capacity of the group should not exceed the sum of the capacities of the individual piles in the group. The settlement of the pile group should not exceed the tolerable settlement limits of the structure. The allowable working uplift load for a pile group should be the lesser of (1) the individual pile design uplift load times the number of piles in the group, (2) 2/3 of the effective weight of the pile group and the soil contained within a block defined by the perimeter of the group and the length of the piles, or (3) 1/2 the effective weight of the pile

STANDARD GUIDELINES FOR THE DESIGN AND INSTALLATION OF PILE FOUNDATIONS

group and soil contained within a block defined by the perimeter of the group and the pile length plus 1/2 the total shear on the peripheral surface of the block.

CHAPTER 6

Design Stresses

6.1 General The design stresses in axial compression in this Standard apply only to the structural capacity of embedded foundation piles that are laterally supported. Unsupported pile lengths should be designed in accordance with Sec. 3.5. Piles should be designed to resist all forces imposed upon them during manufacture, transport, installation, and service. 6.1.1 Use of higher allowable stresses. Allowable stresses greater than those specified for each of the following pile types should be permitted when supporting data justifying such higher stresses are provided. Such substantiating data should include successful pile load testing in accordance with Sec. 4.5, and one or more of the following. (1) Documentation of previous satisfactory performance; (2) a subsurface foundation investigation analysis specifically addressing the site, pile type, and loading conditions anticipated; (3) an analysis by wave equation methods to investigate the driving stresses induced during installation; (4) engineering surveillance of pile installation, including dynamic field measurements when appropriate. The design, analysis, load testing, and installation of the pile foundation utilizing such higher allowable stresses should be under the direct supervision of a registered professional engineer knowledgeable and experienced in soil mechanics and the design and installation of pile foundations.

6.2 Timber Piles 6.2.1 Dimensions and stresses. Timber piles should be any species of wood for which clear wood strength values are given by ASTM D2555. Minimum pile dimensions and other physical characteristics of timber piles should be in accordance with ASTM D25. Allowable design stresses should not exceed those determined in accordance with ASTM D2899, Standard Method for Establishing Design Stresses for Round Timber Piles, unless substantiated by the requirements of Sec. 6.1.1. Determination of critical section for tapered piles is required. 6.2.2 Preservative treatment. Preservative treatment for timber piles and the treatment of pile tops cut-off, should be as specified by American Wood Preservers Association Standard C-3, C-18, and M-4. Treatment should be specifically in accordance with the requirements for land or fresh water use, for foundation piles entirely embedded in the ground, or for marine use. For marine construction, American Wood Preservers Association Standard CIS should apply. 6.2.3 Untreated timber piles. Untreated timber piles should be used only if permanently submerged and not subjected to other deteriorating environments for the service life of the piles. 6.3 Concrete Piles 6.3.1 Reinforced precast concrete piles. Conventionally reinforced precast concrete piles should have a minimum dimension measured through the center of the pile of 8 inches (203 mm). The concrete should have a minimum specified 28day compressive strength (f' c ) of 4000 psi (27.6 MPa). Reinforcing steel should have a minimum yield strength of 40,000 psi (275.8 MPa). The allowable design axial compressive stress should not exceed 33 percent of the specified minimum concrete strength and 40 percent of the specified minimum yield strength of the reinforcement, unless substantiated by the requirements of Sec. 6.1.1. The allowable steel design stress in axial compression should not exceed 30,000 psi (206.8 MPa). 6.3.2 Prestressed precast concrete piles. Prestressed precast concrete piles should have a minimum dimension measured through the center of the pile of 8 inches (203 mm). The concrete should have a minimum specified 28-day compressive strength (f' c ) of 4000 psi (27.6 MPa). The allowable design axial compressive stress applied to the full cross-section should not exceed 33 percent of the specified minimum concrete strength minus 27 percent of the effective prestress force, unless sub-

9

STANDARD GUIDELINES FOR THE DESIGN AND INSTALLATION OF PILE FOUNDATIONS

stantiated by the requirements of Sec. 6.1.1. The effective prestress should not be less than 700 psi (4.8 MPa). 6.3.3 Concrete-filled shell piles. Concretefilled shell piles should have a minimum dimension measured through the center of the pile of 8 inches (203 mm). The concrete should have a minimum specified 28-day compressive strength (f c) of 3000 psi (20.7 MPa). The steel portion of mandrel-driven corrugated steel shells and thin wall pipe with a wall thickness of less than 0.1 inches (2.5 mm) should not be considered load carrying. Shells or tubes should be strong enough to withstand all driving and installation stresses and to resist collapse. The allowable design axial compressive stress should not exceed 33 percent of the specified minimum concrete strength, unless substantiated by the requirements of Sec. 6.1.1. Reinforcing steel should be provided as required to resist bending, lateral and uplift loading, and to prevent separation of concreted piles due to adjacent pile installation, or other construction operations. Reinforcing steel should have a minimum yield strength of 40,000 psi (275.8 MPa). The allowable design stress should not exceed 40 percent of the specified minimum yield strength of the reinforcement, nor 30,000 psi (206.8 MPa). Determination of critical section for tapered piles and other nonuniform piles is required. 6.3.4 Uncased cast-in-place and augered pressure grouted concrete piles. Uncased cast-in-place concrete piles installed by drilling, augering, or driving a temporary casing or mandrel should have a minimum diameter of 8 inches (203 mm). The diameter for design under this Standard should not be greater than the outside diameter of the auger bit, drill, casing, or mandrel used to form the pile shaft. All piles should be designed to resist bending, lateral and uplift loads, and to prevent separation and damage due to installation of adjacent piles or other construction operations. The concrete should have a minimum specified 28-day compressive strength (f c) of 3000 psi (20.7 MPa). The allowable design stress in axial compression should not exceed 33 percent of the specified minimum concrete strength and 40 percent of the specified minimum yield strength of the reinforcing steel, except that the allowable design steel stress should not exceed 30,000 psi (206.8 MPa), unless substantiated by the requirements of Sec. 6.1.1. 6.3.5 Enlarged base piles. Enlarged base piles considered herein are formed by means other than drilling and under-reaming and are not considered as caissons and drilled piers. Enlarged base piles 10

under this Standard include extruded concrete and precast concrete bases. For enlarged bases constructed with uncased compacted concrete shafts, the allowable design compressive stress of the compacted concrete shaft should not exceed 25 percent of the specified minimum 28-day compressive strength, unless substantiated by the requirements of Sec. 6.1.1. For cast-in-place concrete shafts, the provisions of Sec. 6.3.3 or 6.3.4 should govern. For timber or structural steel shafts, the provisions of Sec. 6.2.1 and 6.4 should apply. Precast reinforced concrete base elements should meet the applicable provisions of Sec. 6.3. If designed for tension, the shaft should be connected to the base in a manner to develop the full tensile load capacity of the shaft. Enlarged base piles should be constructed and installed in the same manner, utilizing comparable quantities of material, and should bear in the same strata as successful prototype load test piles on the project. Unless the shaft is designed as a column in accordance with Sec. 3.5, any annular space around the pile shaft should be filled with grout, sand, or other approved material in a manner acceptable to the Engineer to re-establish lateral support around the pile. 6.4 Steel Piles Rolled structural steel sections, steel pipe, and fully welded steel piles fabricated from plates or other rolled sections should conform to one of the appropriate standard specifications. Structural steel piles, rolled and fabricated, shall conform to ASTM A36, ASTM A572, or ASTM A588. Steel pipe piles shall conform to ASTM A252 and have a minimum yield strength of not less than 35,000 psi (248 MPa). Steel encased cast-in-place concrete piles shall conform to ASTM A252, ASTM A283, ASTM A569, ASTM A570, or ASTM A611. 6.4.1 Allowable stresses. Steel piles should be proportioned for direct axial compression so as to not exceed an allowable design stress of 35% of the specified minimum yield strength, unless substantiated by the requirements of Sec. 6.1.1. 6.4.2 Minimum dimensions, rolled steel H piles, and fabricated piles. Rolled structural sections and fabricated shapes should conform to the following minimum dimensions. (1) The flange projections should not exceed 14 times the minimum thickness of metal in either the flange or the web, and the flange widths should not be less than 80% of the depth of the section.

STANDARD GUIDELINES FOR THE DESIGN AND INSTALLATION OF PILE FOUNDATIONS

(2) The nominal depth of the section should not be less than 8 inches. For H sections, this should be measured in the direction of the web. (3) Flanges and webs should have a minimum thickness of 0.375 inches (9.5 mm). Other dimensions may be used if they are substantiated by the requirements of Sec. 6.1.1. 6.4.3 Minimum dimensions, steel pipe piles. Pipe piles should have a minimum nominal outside diameter of 8 inches (203 mm). Steel pipe piles, top-driven and open-ended, should have a minimum wall thickness of 0.25 inches (6.4 mm) for pipe diameters of 14 inches (355 mm) or less, and 0.375 inches (9.5 mm) for pipe diameters greater than 14 inches (355 mm). Pipe of less wall thicknesses may be used when a suitable protective cutting shoe is used or if the pipe is completely filled with concrete. Pipe having a wall thickness less than 0.1 inches (2.5 mm) shall be considered nonload carrying. The allowable design stress for steel pipe filled with concrete after driving should meet the requirements of Sec. 6.4.4. Pipe not filled with concrete should meet the requirements of Sec. 6.4.1. Other dimensions may be used if they are substantiated by the requirements of Sec. 6.1.1. 6.4.4 Steel pipe or tube piles—concrete filled. Steel pipe or tube piles should have a minimum nominal outside diameter of 8 inches (203 mm) and a minimum wall thickness of 0.1 inches (2.5 mm). The allowable design stress for steel pipe or tube piles filled with concrete after driving should not exceed 35 percent of the minimum yield strength of the steel and as detailed further in Sec. 6.4.1. The allowable design axial compressive stress for the concrete fill should not exceed 33 percent of the specified minimum concrete strength. Any reinforcing steel should have a minimum yield strength of 40,000 psi (275.8 MPa). The allowable design stress should not exceed 40 percent of the specified minimum yield strength of the reinforcement, nor 30,000 psi (206.8 MPa). Higher allowable design stresses may be used when substantiated by the requirements of Sec. 6.1.1. Top-driven open-ended piles, subsequently concrete filled, should have a minimum wall thickness of 0.179 inches (4.5 mm), but also not less than necessary to withstand all driving and installation stresses, and prevent collapse. Longitudinally fluted steel tube piles should be designed in accordance with the provisions of this section, but may have a minimum wall thickness of 0.12 inches (3 mm), but also not less than that necessary to resist all driving

and installation stresses, and resist collapse. Such fluted piles should be filled with concrete after driving. If tapered sections are used, determination of critical section is required. 6.4.5 Mandrel-driven shell or tube piles. Mandrel-driven shell or tube piles should be designed in accordance with Sec. 6.3.3. Steel shells or tubes less than 0.1 inches (2.5 mm) should not be considered to be load carrying. Shells or tubes should be strong enough to withstand all driving and installation stresses and to resist collapse. Such piles should be filled with concrete after driving. 6.4.6 Driven caisson-type piles. A caisson pile should denote an open-ended pipe driven to rock, extended by a socket drilled into the rock through the open-end pipe and filled with concrete. If required by the design, reinforcement should be placed prior to concreting and should consist of structural steel sections or reinforcing steel. Pipe, reinforcing steel, and structural steel core sections shall conform to the applicable requirements of this Standard. Minimum diameter of caisson-type piles should be 15 inches. Maximum allowable stresses of pipe, reinforcing, and concrete shall be in accordance with applicable portions of this Standard. Pipe should have a minimum wall thickness per the requirements of Sec. 6.4.3. The maximum allowable stress on the structural steel core should be 50 percent of the minimum yield strength. The allowable design stress for steel pipe having wall thicknesses of 0.1 inches (2.5 mm) or more filled with concrete after driving should not exceed 35 percent of the minimum yield strength of the steel and as detailed further in Sec. 6.4.1. The allowable design axial compressive stress for the concrete fill should not exceed 33 percent of the specified minimum concrete strength. Any reinforcing steel should have a minimum yield strength of 40,000 psi (275.8 MPa). The allowable design stress should not exceed 40 percent of the specified minimum yield strength of the reinforcement, nor 30,000 psi (206.8 MPa). The maximum allowable stress on other steel core material should not exceed 40 percent of the minimum yield strength (35,000 psi), nor 30,000 psi (206.8 MPa). Higher allowable design stresses may be used when substantiated by requirements of Sec. 6.1.1. 6.4.7 Composite and other pile types. Piles of a type, configuration, or material not specifically covered by this Standard, should conform to all applicable provisions of the Standard, including the provisions of Sec. 6.1.1. Such piles, or pile types, having a design load of 25 tons (222 kN) or greater should have the capacity proven by load test in 11

STANDARD GUIDELINES FOR THE DESIGN AND INSTALLATION OF PILE FOUNDATIONS

accordance with Sec. 4.5, as appropriate. Composite piles, made up of different pile types, should have their shaft capacity determined by the critical section that may be the component with lesser strength. The connection or joint between the two component parts should be designed and constructed so as to prevent separation of the components during installation or thereafter, and should provide appropriate lateral stability. 6.5 Mini-Piles The use of concrete, steel, composite, or pipe piles with minimum dimensions less than those stated in Sec. 6 should be permitted provided that, in the sole judgment of the Engineer, sufficient data are available to indicate that the proposed pile type can be reliably constructed to provide the required ultimate capacity. Such data should include adequate provision for quality control as well as either acceptable evidence of long-term performance under similar loading conditions or satisfactory load tests in similar soil conditions. 6.5.1 Mini-pile strength requirements and capacity. The maximum design load for mini-piles designed and constructed under this section should not exceed 25 tons (222 kN), except as allowed under Sec. 6.1.1 and 6.4.7. The strength requirements and capacity of mini-piles should be as specified in Sec. 4 except that the mini-piles should develop ultimate capacities (as specified in Sec. 4.2.1) of at least 250 percent of the design load. 6.5.2 Mini-pile quality control. For all piles constructed under this section, the Engineer should assess the effects that small deviations in the crosssectional dimensions, locations, and material strengths of mini-piles can have on pile capacity. The Engineer should include or modify the specifications for construction of mini-piles under this section to include provisions for adequate verification of minimum pile cross-sectional dimensions, locations, and material strengths. Alternatively, the Engineer may increase the safety factor in the pile design to adequately allow for the effect possible deviations in these parameters may have on pile capacity.

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CHAPTER 7

Construction and Layout Guidelines for Pile Design

7.1 General The provisions of this section cover constructionrelated design considerations. Such design considerations should include, but not be limited to, the effects that jetting, pre-drilling, sequence of installation of individual piles, hammer energies, auger torque, hammer or auger types, grout pump capacities, and potential installation problems, could have on the pile foundation construction and subsequent performance. The pile design must address, but not necessarily limit, installation means, methods, and criteria. The design should require that installation be consistent with the subsurface conditions, pile type and materials, and the design loads. Installation procedures that do not accomplish, or that diminish the proper functioning of the foundation, should be excluded. Contractors and owners should be made aware of any installation restrictions or provisions in the design. 7.2 Deviation At the sole discretion of the Engineer, piles that deviate from the specific plan tolerances in the following may be accepted, but it should be shown that the pile, or pile group, as constructed will satisfy the strength, service, and safety requirements of this Standard. 7.3 Driving Stresses Installation procedures, pile-driving hammers, pile and hammer cushioning, pile lengths, and other factors affecting the driving stresses imparted to the pile shaft should be evaluated by both the Engineer and contractor. In situations where the Engineer determines there is uncertainty about the stresses induced in the pile shaft or the potential for damage to the pile shaft during installation, an elastic wave equation analysis of the pile-hammer-soil system should be conducted. This analysis may be supplemented by field measurements and testing as specified in Sec. 4.5. Such analysis should be in accor-

STANDARD GUIDELINES FOR THE DESIGN AND INSTALLATION OF PILE FOUNDATIONS

dance with recognized engineering practices. Driving stresses calculated or measured as previously outlined should not exceed, at any point along the pile shaft, the values shown in Table 7.1. 7.4 Location and Axial Alignment Tolerances Piles should be installed so that the axial alignment of the top 10 feet of the pile is within the specified alignment, but should not be greater than 4 percent out of alignment. If alignment tolerances are critical to the design, provisions to verify proper alignment should be required. For individual piles or piles in groups of four or less, the tops of piles at cut-off elevations should be within 3 inches (76 mm) of plan locations except that tops of timber piles should be within 6 inches (152 mm) of plan locations. These location and alignment tolerances should be considered in the pile design. For all piles in groups of five or more, the tops of piles at cut-off elevation should be within 6 inches (152 mm) of plan locations. Furthermore, the as-driven center of any pile group at cutoff elevation should be within 3 inches (76 mm) of the plan location. 7.5 Obstructions and Hard Strata If piles are to be installed in obstructed ground or the pile tip is to bear on hard strata, the selection of pile type and installation methods should consider the possible effects on pile alignment, location, and damage to shaft and tip. Methods and means to protect the pile tip include cast steel points, prefabricated points, and protective boots for driven piles. High torque auger motor boxes and auger cutting bits should be considered along with increased field verifications for augered pressure grouted piles.

7.6 Design Modifications Due to Field Conditions If the tolerances specified under Sec. 7.4 are exceeded, the extent of any overloading of the piles, pile cap, or other parts of the structure should be investigated by the Engineer. If after the completion of such investigation, in the judgment of the Engineer correction is necessary, suitable remedial measures should be designed and constructed. 7.7 Cross-Sectional Area If the cross-section of a cast-in-place, cased, uncased, or augered pressure grouted pile is found to be reduced, or if the shaft of any other pile type is damaged, corrective actions to preclude further occurrences or damage should be considered. The Engineer should analyze the reduced cross-section or damaged pile to determine that the remaining strength is satisfactory. If after the completion of such analysis, correction is necessary, suitable remedial measures should be designed and constructed. 7.8 Pile Spacing Individual pile spacing as measured center-tocenter at cut-off elevation should not be designed less than 2.5 times the largest diameter or width of any portion of the pile including the tip, and should not be less than 24 inches (609 mm). For sequentially installed, uncased cast-in-place concrete piles, the spacing should not be less than 6 pile diameters or greater if necessitated by site conditions; however, normal spacing may be used if piles are installed in alternate sequence and the concrete is permitted to harden before installing intermediate piles.

TABLE 7.1 Maximum driving stresses.* Maximum Compression

Maximum Tension

0.85(f'c) - fp, 0.85(f'c)

3(Vf c) + f,.

0.9 (Fy) 2.5 (o-J

0.9 (Fy) 2.5 (a.)

1. Prestressed Precast Concrete

2. Precast Concrete 3. Steel 4. Timber

3(Vfc)

NOTE: AISI recommends 1.25 Fy for both compression and tension for rolled H-piles conforming to Sec. 6.4.2 and pipe piles conforming to Sec. 6.4.3. f'c = concrete compressive strength at time of driving f'pe = effective prestress force (after losses) Fy = minimum yield strength per certified mill test reports cra = allowable design strength * Except as allowed by Sec. 6.1.1

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STANDARD GUIDELINES FOR THE DESIGN AND INSTALLATION OF PILE FOUNDATIONS

The possible interference of one pile with another during installation must be considered in determination of pile spacing and installation sequence. Spacing and installation sequence should not cause heave or damage to installed piles when installing adjacent piles. 7.9 Caps and Bracing Except for seismic design, the tops of all piles cut off at or below ground surface should be embedded at least 3 inches (76 mm) in concrete caps that extend horizontally at least 4 inches (101 mm) beyond the periphery of the pile, both as designed and as built. Reinforcement normally should be placed over the pile heads. Concrete pile caps should be designed for moment and shear as deep beams if applicable. Transfer of horizontal, uplift, and moment loads should be accounted for in the design. For seismic design, the Engineer should design the pile connections so as to ensure that imposed curvatures and displacements under the design earthquake motions will not impair the ability of the pile to sustain design loads with a safety factor of at least 1.0. Except for single piles, two-pile groups, and piles supporting a wall load, piles in groups should be arranged in a symmetrical pattern so that the centroid of the pile group should coincide with the resultant of the applied load. A two-pile group is considered braced in the direction of the axis connecting the two piles, but requires bracing in the direction normal to this axis. A single pile must be braced in two directions, not less than 60 degrees, or more than 120 degrees apart. Piles supporting walls should be located alternately in lines spaced at least one-half the pile diameter at cut-off elevation, and located symmetrically under the center of gravity of the wall load carried, unless adequately braced laterally. Bracing should be designed to resist the loads determined by analysis, but not less than 3 percent of the total load of the piles being braced, plus moment loads due to the allowable eccentricity of loading resulting from pile mislocation as noted in Sec. 7.4 and 7.6. Piles supporting or restrained by conventionally reinforced or post-tensioned concrete slabs will be considered as braced, if analysis shows the slab meets the foregoing bracing requirements.

14

7.10 Splices Splices and composite pile connectors should provide for and maintain alignment and position of the component parts of the pile during installation and subsequent thereto and should develop the required design strength of the pile section considering handling, driving, and design load stresses, but in no case less than 50% of the pile strength in bending. 7.11 Multiple Pile Types, Capacities, or Methods of Installation Special provisions are required whenever it is proposed to: (1) Construct a foundation for a structure utilizing piles of more than one type or capacity; (2) modify an existing foundation by the addition of piles of a type or capacity other than those existing; (3) construct or modify a foundation utilizing different methods of installation or different types or capacities of pile installation equipment; or (4) support part of the structure on piles and part on footings. If parts of the structure are supported on different types, capacities, or modes of piling or foundations, they should be separated by suitable joints providing for differential movement. Alternatively, the Engineer should show that the probable differential settlements will not result in instability of the structure or stresses in the structure in excess of the allowable values. In the case of repair of a portion of an existing foundation, the Engineer should inform the owner of the possible negative effects the repair of a portion of the foundation may have on the remainder of the structure. The provisions of the Standard relating to required load tests should apply separately and distinctly to each different type or capacity of piling, method of installation, or type and capacity of equipment used; except where a comparative analysis of the behavior of the different pile types, capacities, or methods of installation indicates that data from one type or capacity can be reliably extrapolated to the other pile types and capacities.

STANDARD GUIDELINES FOR THE DESIGN AND INSTALLATION OF PILE FOUNDATIONS

CHAPTER 8

Installation Guidelines for Pile Construction

8.1 General The provisions of this section cover construction and installation-related considerations. Construction considerations should include the effects of jetting, pre-drilling, sequence of installation of individual piles, lateral soil displacement, heave, required pile penetrations, hammer energies, hammer types, auger motor torque and energy, grout pump capacities, adjacent properties, hard strata, collapse problems, and other potential installation problems. The installation must be consistent with the subsurface conditions, pile type and materials, and the design loads. 8.2 Installation Equipment Impact hammers common to the industry powered by gravity, air, steam, hydraulic, or diesel combustion should be used. Installation by other means may be acceptable if sufficient documenting details are available for evaluation. Vibratory hammers are acceptable if the pile capacity is verified by tests and the installation of production piles is controlled according to power consumptions and rates of penetration or other means acceptable to the Engineer that assure pile capacity equals or exceeds that of the test pile. 8.2.1 Selection of driving system. Acceptability of the pile hammer, hammer cushion, pile cushion, drive head, and follower if used should be verified by satisfactory prior experience or by analysis using one-dimensional wave theory, by pile load tests, or dynamic measurements. 8.2.2 Followers. The Engineer should determine and document the required changes in driving criteria when a follower is used, if applicable. The onedimensional wave equation can be used for this analysis. All followers must be held in proper alignment with the pile and hammer. 8.3 Equipment for Augered Pressure Grouted Piles 8.3.1 Augering equipment. The auger flighting should be continuous from the auger bit to the top

of the auger without gaps or other breaks. The auger flighting should be uniform in diameter throughout its length and should be the diameter specified for the piles within 3 percent. The discharge hole for the grout should be located at the bottom of the auger bit, below the cutting teeth. Augers over 40 feet (12 m) in length should contain a middle guide. The auger leads should be prevented from rotating by a stabilizing arm or by firmly placing the bottom of the leads into the ground or by other acceptable means. Leads should be marked at 1 foot (300 mm) intervals to facilitate measurement of auger penetration and rates of withdrawal. 8.3.2 Mixing and pumping equipment. Only pumping and mixing equipment approved by the Engineer should be used in the preparation and handling of the grout. A screen to remove oversize particles should be placed at the pump inlet. All oil or other rust inhibitors should be removed from mixing drums and pumps prior to using. All materials should be such as to produce an homogeneous grout of the desired consistency. Use of a flow cone is recommended for controlling grout consistency. The grout pump should be a positive displacement pump capable of developing displacement pressures at the pump not less than 350 psi (2,400 kPa). The grout pump should be provided with a pressure gauge in clear view of the equipment operator and the Engineer or inspector. The grout pump should be calibrated at the beginning of the work to determine the volume of grout pumped per stroke. A positive method of counting grout pump strokes should be provided by the pile contractor. A second pressure gauge, if required, should be provided close to the auger rig, again in clear view of the Engineer or inspector. 8.4 Operations Pile-driving or other installation equipment should be supported and aligned in a manner that allows the hammer or auger to follow the pile without undue restraint by the hoisting line, leaders, or other devices. The hammer or auger should be aligned with the axis of the pile. The hammer should be equipped with a drive head or cap that minimizes eccentric hammer blows. Followers, when used, should be rigged in a similar manner. Open-end diesel hammers should be equipped with a suitable stroke indicator. Closed-end diesel hammers should be equipped with a suitable bounce chamber gauge, and used at appropriate intervals only to verify hammer performance. At final driving, the pile-driving hammer should be operated at the specified stroke, speed, and/or 15

STANDARD GUIDELINES FOR THE DESIGN AND INSTALLATION OF PILE FOUNDATIONS

energy for air, steam, or hydraulic hammers. For diesel hammers, operation should be at the specified stroke or equivalent stroke, and speed. Diesel hammers should not exhibit abnormal operation due to pre-ignition, poor ignition, or over-heating. At final penetration for augered cast-in-place piles, the auger motor should be operated at specified speed and torque. Auger withdrawal rates for augered pressure grouted piles should be correlated with pumping rates, volumes, shaft diameters, and site-specific details, to assure that the proper quantity of grout is installed in the pile shaft. Such withdrawal rates must be related to those used for load-tested piles. The auger should not be allowed to jump, jerk, or rapidly accelerate during withdrawal. The withdrawal should be at a steady speed consistent with that used for tested piles. 8.5 Continuous Driving Preliminary to final seating, the piles should be driven without interruption for the preceding 5 feet. This provision is to assure that final driving resistance is not increased by soil freeze, when such increase is not taken into account for the driving criteria. The Engineer may modify this provision based on field experience and/or static/dynamic load-test results. 8.6 Pre-Excavation Spudding, jetting, augering, wet-rotary drilling, or other methods of pre-excavation should be used only as prescribed and documented by the Engineer and only in the same manner as used for piles subjected to static or dynamic load testing. When permitted, such procedures should be carried out in a manner that will not impair the carrying capacity of the piles already in place, or the safety of existing structures. Pre-excavation should be stopped at least 5 feet (1.5 m) above the final expected pile tip elevation and at least 5 feet (1.5 m) above the tip elevation of any pile previously driven that is within 6 feet (1.8 m) of the pre-excavation. These provisions may be waived when piles are end-bearing on rock or hardpan. Where possible, piles should be installed to a minimum of 5 feet (1.5 m) below the depth of any pre-excavation, until the required penetration resistance and/or depth is obtained. If there is evidence that pre-excavation has disturbed the load bearing capacity of previously installed piles, those piles that have been disturbed should be restored to conditions meeting the requirements of this Standard by re-driving or by other means or methods acceptable

16

to the Engineer. Re-driving or other remedial measures should be instituted after the pre-excavation operations in the area have been completed. 8.7 Heaved Piles A pile type should be used that will minimize or eliminate heave in the soil into which it will be driven. Level readings to check on pile heave should be made at the start of pile driving and should continue until the Engineer determines that such checking is no longer required. Such level readings should be taken immediately after the pile has been installed, before adjacent piles are driven, and again after piles within a radius of 50 feet have been installed. If pile heave of l/8th inch or more is observed, accurate level readings referenced to a fixed datum should be taken on all piles immediately after installation and periodically thereafter as adjacent piles are driven to determine the pile heave range. All piles that have been heaved more than 0.25 inches should be re-driven to the required penetration resistance or remediated as directed by the Engineer. For corrugated pile shells such level readings should be taken on a pipe telltale resting on the bottom closure plate at the pile tip. Concrete should not be placed in pile casings until pile driving has progressed beyond the heave range. If either ground heave, or pile heave, is observed when installing uncased, insufficiently reinforced cast-in-place concrete piles, the piles should be investigated for continuity and structural integrity and if such cannot be determined to the satisfaction of the Engineer, the pile should be abandoned and replaced, using methods to eliminate heave, or a pile type not subject to heave damage. If pile heave is detected for pipe, shell, or tube piles filled with concrete, the piles may be re-driven after the concrete has obtained sufficient strength and if a proper pile-hammer cushion system, satisfactory to the Engineer, is used. Uncased, shell piles, or augered pressure grouted piles that may be subjected to heave range should be adequately reinforced. If spliced, jointed, or segmental piles, including enlarged base piles, are installed under conditions of ground heave, the splices and joints should be designed and constructed to prevent separations along the pile. Concreted, uncased cast-in-place piles should be permitted to set up before driving subsequent piles that could cause heave. 8.8 Installation Sequence Individual piles and pile groups should be installed in such sequence that:

STANDARD GUIDELINES FOR THE DESIGN AND INSTALLATION OF PILE FOUNDATIONS

(1) The carrying capacity of previously installed piles is not reduced; (2) the soil surrounding the pile is not compacted to the extent that other piles in the group cannot be installed properly; and (3) ground movement that would damage or displace adjacent structure, piles, or utilities is prevented.

8.9 Cast-in-PIace Concrete Concrete should be designed, mixed, and placed so as to preclude segregation and ensure that the entire volume of the pile casing is filled; or for uncased piles, to ensure that the pile has its full cross-section throughout its length and does not contain inclusions or foreign matter. When concrete is placed, pile casings or holes should be free of foreign matter. Water should be removed so that concrete is placed in not more than 2 inches of water. Alternatively, appropriately designed concrete may be placed in water by acceptable pumping or tremie means. Conventional structural concrete placed into dry piles should have a slump of 4 to 7 inches, with a maximum aggregate size of 3/4 inch. Concrete should be deposited in a rapid continuous operation through a discharge hose, or steep-sided funnel having a discharge opening smaller than the diameter of the pile being filled, and centered over the pile casing or hole. For difficult placement conditions, such as those involving piles containing heavy reinforcement or very long piles, or piles installed on steep batters or inclinations, concrete should contain a reduced quantity of 3/4 inch aggregate with corresponding increase in fine aggregate and cement, and should be placed as required for conventional structural concrete. Concrete to be placed by pumping or tremie means should be properly designed and mixed for the placement method. Concrete grout placed through an auger should be designed to be pumpable and to hold solids in suspension. The consistency of the mix should be determined for each batch or each truck by use of a flow cone (U.S. Army Corps of Engineers CE CRD-C79 or other standardized method) for assuring uniform batch consistency. Grout and concrete used in pile construction should be tested in accordance with ASTM Standards.

investigation by the Engineer for pile damage or breakage. Pile repairs and modifications should be subject to the approval of the Engineer. Significant differences in pile lengths in a cluster or between adjacent pile clusters should also be cause for investigation. The investigation should consider the possibility of pile-driving damage, driving obstructions, variations in the thickness and quality of the supporting materials, and deviations in pile alignment due to irregular end-bearing conditions.

8.11 Relaxation When piles are to be driven into materials that could cause a reduction in bearing capacity with time, for example, shale, dense saturated silts, or dense saturated fine sands, a representative number of previously driven piles should be re-struck after initial driving as scheduled by the Engineer, using the same hammer-cushion-follower system, properly warmed up and operating in the same manner as for the original driving. Time-dependent strength characteristics of the soil-pile system should be incorporated into the design. If a reduction in driving resistance is observed, the Engineer should consider altering the design based upon static or dynamic load tests or the reduced driving resistances.

8.12 Soil Freeze or Setup When piles are driven into soils that could set up or "freeze" with time after pile driving stops, reasonable efforts should be made to avoid interruptions during driving of each pile. The penetration resistance should be verified by re-driving a representative percentage of the piles following a period of set-up time as determined by the Engineer if the required final penetration resistance is predicated on soil freeze. It is recommended that design based on utilizing soil freeze be verified by static or dynamic load testing.

8.13 Obstructions If driving obstructions are encountered, special provisions approved by the Engineer should be taken to prevent pile damage.

8.14 Pile Protection 8.10 Driving and Installation Anomalies During installation, any instance of an anomalous increase or decrease of driving resistance, auger penetration, or grout volume usage incompatible with the soil profile should be cause for an

When piles are installed through obstructing layers or through boulder formations or when piles are essentially tip bearing and installed to a hard stratum, consideration should be given to pile protection such as tip reinforcement.

17

STANDARD GUIDELINES FOR THE DESIGN AND INSTALLATION OF PILE FOUNDATIONS

8.15 Bent, Dog-Legged, or Collapsed Piles Where piles have been bent during installation, the bearing capacity should be analyzed or proven by tests. If such analysis or test indicates inadequate capacity, corrective measures as determined by the Engineer should be taken. Such measures may include use of bent piles at reduced capacity, installation of additional piles, strengthening of bent piles, or replacement of bent piles. Pipe or shell piles that collapse due to earth pressures or forces from the installation of proximate piles should be replaced or repaired to the Engineer's satisfaction. 8.16 Pile Installation and Testing Records See Sec. 2.10. Records should include a chronological log of pile installation operations, individual pile installation logs of each pile installed, and the design and fabrication details of each pile. The individual installation log for each pile should include the type and extent of any predrilling or jetting done, pile and hammer cushion conditions, length of pile driven, and the driving log in blows per foot (30 cm) for at least the last 5 feet (1.5 m) of penetration and in blows per inch (25 mm) for at least the last 6 inches (15 cm) of penetration; and for augered cast-in-place piles, records should document the rate of auger penetration at termination, the depth of each pile, rate of auger withdrawal, and the number of pump strokes. Pump strokes must be recorded sequentially for each foot (or for some multiple feet) of auger withdrawal, to ensure a uniform placement of grout within the shaft. Pile tip elevations referenced to a fixed and permanent datum should be recorded. Records should include the details of the driving equipment, consisting of at least: hammer, make and model, hammer ram weight and stroke at final driving, power supply and rating, operating pressure for double and differential steam/air hammers, details of hammer cushion assembly including materials and dimensions, details of pile cushion (if used) including materials and dimensions, weight of drive head or cap and details of follower (if used) including material and dimensions; and for augered pressure grouted piles, auger motor torque and energy, pump capacity, and pump pressure. Interruptions to installation of all piles should be recorded along with the cause, extent, and time. Penetration measurements made for the purpose of determining the resistance to driving should not be made when pile heads are damaged to an extent that may affect measured penetration, nor should they be made immediately after fresh cushion 18

blocks have been inserted under the striking part of the hammer or on the piles. At least 20 blows of the hammer should occur after fresh cushion blocks are inserted before final penetration measurements are made. 8.17 Probe Piles Probe or indicator piles may be installed in permanent locations, in advance of production installation. Probe piles provide valuable information as to equipment and material performance and assist in correlation of pile installation with soil boring logs. Probe piles, with instrumentation, should be used when project conditions allow. Selection of one of the probe piles for load testing allows choosing test piles after a few representative portions of the piles have been installed. Full depth installation records should be maintained. Where group effects may be significant, consideration should be given to driving multiple probe piles in a representative group.

CHAPTER 9

Applicable Standards

The following standards are considered to be the current published revision at the time of the publication of this Standard. 9.1 ASTM Standards American Society for Testing and Materials 100 Barr Harbor Drive West Conshohocken, PA 19428-2959 A 29

A 36 A 82 A 185

A 242

Standard Specification for General Requirements for Hot-Rolled and ColdFinished Carbon and Alloy Steel Bars Specification for Structural Steel Specification for Cold-Drawn Steel Wire for Concrete Reinforcement Standard Specifications for Welded Steel Wire Fabric for Concrete Reinforcement Standard Specification for HighStrength Low-Alloy Steel

STANDARD GUIDELINES FOR THE DESIGN AND INSTALLATION OF PILE FOUNDATIONS

A 252 A 245

A 283

A 322 A 366 A 416

A 421 A 499 A 569

A 570

A 572

A 588

A 615

A 616

A 617

A 690

A 706

A 722

Specification for Welded and Seamless Steel Pipe Piles Standard Specifications for Flat-Rolled Carbon Steel Sheets of Structural Quality Specification for Low and Intermediate Tensile Strength Carbon Steel Plates, Shapes, and Bars Standard Specification for Hot-Rolled Alloy Steel Bars Specification for Steel, Carbon, ColdRolled Sheet, Commercial Quality Specification for Uncoated Seven Wire Stress-Relieved Strand for Prestressed Concrete Specification for Uncoated StressRelieved Wire for Prestressed Concrete Standard Specification for Hot-Rolled Carbon Steel Bars and Shapes Standard Specification for Hot-Rolled Steel, Carbon (0.15 Maximum, Percent), Sheet and Strip, Commercial Quality Standard Specification for Hot-Rolled Carbon Steel Sheet and Strip, Structural Quality Specification for High-Strength LowAlloy Columbium Vanadium Steel of Structural Quality Specification for High-Strength LowAlloy Structural Steel with 50 ksi Minimum Yield Point to 4 Inch Thick Specification for Deformed and Plain Billet-Steel Bars for Concrete Reinforcement Specification for Rail-Steel Deformed and Plain Bars for Concrete Reinforcement Specification for Axle-Steel Deformed and Plain Bars for Concrete Reinforcement Specification for High-Strength LowAlloy Steel H-Piles and Sheet Piles for Use in Marine Environments Specification for Low-Alloy Steel Deformed Bars for Concrete Reinforcement Specification for Uncoated HighStrength Steel Bars for Prestressing Concrete

C 39

Standard Method of Test for Compressive Strength of Cylindrical Concrete Specimens C 78 Standard Method of Test for Flexural Strength of Concrete (Using Simple Beam with Third Point Loading) C 143 Standard Method of Test for Slump of Portland Cement Concrete C 150 Standard Specification for Portland Cement C 172 Standard Method of Sampling Fresh Concrete C 260 Standard Specification for AirEntraining Admixtures for Concrete C 309 Standard Specification for Liquid Membrane-Forming Compounds for Curing Concrete C 330 Standard Specifications for Light Weight Aggregates for Structural Concrete C 360 Standard Method of Test for Ball Penetration in Fresh Portland Cement Concrete C 494 Standard Specification for Chemical Admixtures for Concrete C 496 Standard Method of Test for Splitting Tensile Strength of Cylindrical Concrete Specimens C 595 Standard Specification for Blended Hydraulic Cements C 937 Standard Specification for Grout Fluidifier for Pre-Placed Aggregate Concrete C 942 Standard Test Method for Compressive Strength of Grouts for Pre-Placed Aggregate Concrete in the Laboratory C 943 Standard Practice for Making Test Cylinders and Prisms for Determining Strength and Density of Pre-PlacedAggregate Concrete in the Laboratory C 1019 Standard Method of Sampling and Testing Grout D 25 Specification for Round Timber Piles D 31 Standard Method of Making and Curing Concrete Compressive and Flexural Strength Test Specimens in the Field D 33 Standard Specifications for Concrete Aggregates D 1143 Method of Testing Piles Under Static Axial Compressive Load 19

STANDARD GUIDELINES FOR THE DESIGN AND INSTALLATION OF PILE FOUNDATIONS

D 1760 Specification for Pressure Treatment of Timber Products

9.3 ACI Standards American Concrete Institute P.O. Box 19150, Redford Station Detroit, MI 48219-0150

D 2555 Methods for Establishing Clear Wood Strength Values D 2899 Method for Establishing Design Stresses for Round Timber Piles D 3689 Method for Testing Individual Piles Under Static Axial Tensile Load

ACI 304

D 3966 Method of Testing Piles Under Lateral Loads D 4945 Standard Test Method for High-Strain Dynamic Testing of Piles

ACI 306

9.2 AWPA Standards American Wood Preservers Association P.O. Box 286 Woodstock, MD 21163-0286 C3 CIS M4

Piles-Preservative Treatment by Pressure Processes Standard for Pressure Treated Material in Marine Construction Standard for the Care of Preservative Treated Wood Products

ACI 305

ACI 308 ACI 309 ACI 315

ACI 318 ACI 347 ACI 403 ACI 517

20

Recommended Practice for Measuring, Mixing, Transporting, and Placing Concrete Recommended Practice for Hot Weather Concreting Recommended Practice for Cold Weather Concreting Recommended Practice for Curing Concrete Recommended Practice for Consolidation of Concrete Manual of Standard Practice for Detailing Reinforced Concrete Structures Building Code Requirements for Structural Concrete Recommended Practice for Concrete Formwork Guide for Use of Epoxy Compounds with Concrete Recommended Practice for Atmospheric Pressure Steam Curing of Concrete

(2) a static analysis, construction load testing, dynamic analysis and testing; and (3) inspection by qualified personnel under the direction of the Engineer (see Sec. 1.4).

APPENDIX A

Partial Factors of Safety

The provisions for these minimum partial safety factors do not consider high-risk construction environments, uncertainty of maximum transient loads (tornado, hurricane, wave, seismic, etc.), or a consequence of failure that is unusually great, or any other abnormal condition. The foundation design should consider aspects relative to

A.I Introduction The capacity of single piles in axial compression should provide an adequate safety factor against failure due to insufficient soil-pile interface strength or structural (material) capacity. The minimum overall factor of safety applied to ultimate soil-pile interface strength (Fs) may be determined as the product of partial safety factors that consider:

(1) the variability of subsurface conditions across the site; (2) the reliability of soil strength data, confidence in the magnitude of structural loads; (3) the longevity of the structure (temporary, normal service, monument, etc.); (4) environmental effects; (5) confidence in the magnitude of design loads;

(1) the uncertainties inherent in determination of pile capacity, Factor F,, from Table A.I, and (2) the uncertainties inherent in the ability to install the pile without structural defects, Factor F2, from Table A.2 where

TABLE A.2 Partial safety factor F2 (minimum values).

Fs = F, X F2. This method of partial factors of safety allows the use of a global factor of safety more proportionally reflecting the uncertainties in the pile foundation design and construction than a single uniform factor of safety. This method allows for revisions to the usual arbitrary factors of safety when specific criteria are met. Some of these criteria are:

Pile Type

with Inspection*

Concrete-filled, closed-end steel pipe piles Steel H and open-ended steel pipe Timber, precast concrete, and concrete-filled shell piles Uncased cast-in-place concrete piles with temporary casing Augered, pressure grouted piles Uncased cast-in-place concrete piles without temporary casing

(1) a reliable knowledge of the subsurface conditions;

1.0 1.1 1.2 1.3 1.3 1.8

* Full time, on-site monitoring by a qualified engineer. (See Sec. 1.4.)

TABLE A.I Partial safety factor F, (minimum values). Design Axial Loads T

889kN)

From Pile Load Test coupled with wave equation and static analysis o

1.5

1.5

1.6

1.8

From Dynamic Measurements coupled with wave equation and static analysis *

1.5

1.6

1.7

2.0

From wave equation and static analysis'"

1.5

1.8

1.9

0

From driving formulas and static analysis H or other methods

1.5

2.0

0

0

Capacity Determination Method

T

o static analysis per Sec. 4.3 0 to be established by the Engineer

21

STANDARD GUIDELINES FOR THE DESIGN AND INSTALLATION OF PILE FOUNDATIONS

TABLE A.3-b Minimum global factors of safety resulting from Tables A.I and A.2 for pile design loads 16 to 40 tons (142 to 356 kN).

TABLE A.3-a Minimum global factors of safety resulting from Tables A.I and A.2 for pile design loads less than 15 tons (< 133 kN). Testing/Analysis Criteria Pile Type

1

2

3

4

Concrete-filled, closed-end steel pipe piles Steel H and open-ended pipe Timber, precast concrete, and concrete-filled shell piles Uncased cast-in-place concrete piles with temporary casing Augered pressure grouted piles Uncased cast-in-place concrete piles without temporary casing

1.5

1.5

1.5

1.5

1.7 1.8

1.7 1.8

1.7 1.8

1.7 1.8

2.0

2.0

2.0

2.0

2.0 2.7

2.0 2.7

* 2.7

* 2.7

Testing/Analysis Criteria

Testing/Analysis Criteria Pile Type

1

2

3

4

Concrete-filled, closed-end steel pipe piles

1.5

1.6

1.8

2.0

Steel H and open-ended pipe Timber, precast concrete, and concrete-filled shell piles Uncased cast-in-place concrete piles with temporary casing Augered pressure grouted piles Uncased cast-in-place concrete piles without temporary casing

1.7 1.8

1.8 2.0

1.9 2.2

2.2 2.4

2.0

2.1

2.3

2.6

2.0 2.7

2. 1 2.9

* 3.2

* 3.6

Testing/Analysis Criteria

1 . From pile load test coupled with wave equation and static analysis 2. From dynamic measurements coupled with wave equation and static analysis 3. From wave equation and static analysis 4. From driving formulas and static analysis or other methods

1 . From pile load test coupled with wave equation and static analysis 2. From dynamic measurements coupled with wave equation and static analysis 3. From wave equation and static analysis 4. From driving formulas and static analysis or other methods

* Note: Wave equation and driving formula techniques are inappropriate for augered pressure grouted piles and other drilled uncased castin-place concrete piles.

* Note: Wave equation and driving formula techniques are inappropriate for augered pressure grouted piles and other drilled uncased castin-place concrete piles.

TABLE A.3-C Minimum global factors of safety resulting from Tables A.I and A.2 for pile design loads 41 to 100 tons (364 to 889 kN).

TABLE A.3-d Minimum global factors of safety resulting from Tables A.I and A.2 for pile design loads over 100 tons (> 889 kN). Testing/Analysis Criteria

Testing/Analysis Criteria Pile Type

1

2

3

4

Pile Type

1

2

3

4

Concrete-filled, closed-end steel pipe piles Steel H and open-ended pipe Precast concrete and concrete-filled shell piles Uncased cast-in-place concrete piles with temporary casing Augered pressure grouted piles

1.6

1.7

1.9

0

1.8

2.0

O

O

1.8 1.9

1.9 2.0

2.1 2.3

O O

2.0 2.2

2.2 2.4

O O

O O

2. 1

2.2

2.5

O

2.3

2.6

O

O

2.1

2.2

*

*

2.9

3.1

3.4

O

Concrete-filled, closed-end steel pipe piles Steel H and open-ended pipe Precast concrete and concrete-filled shell piles Uncased cast-in-place concrete piles with temporary casing Augered pressure grouted piles Uncased cast-in-place concrete piles without temporary casing

2.3 3.2

2.6 3.6

* 0

* O

Uncased cast-in-place concrete piles without temporary casing

Testing/Analysis Criteria

Testing/Analysis Criteria

1 . From pile load test coupled with wave equation and static analysis 2. From dynamic measurements coupled with wave equation and static analysis 3. From wave equation and static analysis 4. From driving formulas and static analysis or other methods

1. From pile load test coupled with wave equation and static analysis 2. From dynamic measurements coupled with wave equation and static analysis 3. From wave equation and static analysis 4. From driving formulas and static analysis or other methods

* Note: Wave equation and driving formula techniques are inappropriate for augered pressure grouted piles and other drilled uncased castin-place concrete piles.

* Note: Wave equation and driving formula techniques are inappropriate for augered pressure grouted piles and other drilled uncased castin-place concrete piles.

0 Not recommended; however may be established by the Engineer for pile types and situations in which he or she has confidence.

O Not recommended; however may be established by the Engineer for pile types and situations in which he or she has confidence.

22

STANDARD GUIDELINES FOR THE DESIGN AND INSTALLATION OF PILE FOUNDATIONS

(6) (7) (8) (9)

number of piles in a group; pile type; installation means; and testing, construction surveillance, and integrity verification.

A.2 Application The partial safety factor F, is taken from Table A. 1 as a function of the method used to predict the ultimate geotechnical capacity of a pile, Pu]1, and the design load category. These factors assume (1) information has been obtained and documented to reflect confidence in predicting the variability of the subsurface conditions and the strength/deformation properties of the subsurface materials; (2) reasonable confidence that the pile material will exceed the design service life of the structure; and (3) reasonable confidence in service and transient loads. The factor F2 is selected from Table A.2 as a function of the proposed pile type, and method of

installation. Factor F2 assumes full-time on-site monitoring of the installation by a qualified representative of the Engineer (see Sec. 1.4). The global factor of safety Fs is then calculated as the product of F, and F2. Tables A.3-a through A.3-d show the various global factors of safety resulting from partial factors of Tables A. 1 and A.2. The resulting Puu/Fs must be consistent with the original design considerations. Subsequent to the determination of the design capacity for soil/rock resistance, the structural design capacity of the pile should be evaluated according to provisions of Sec. 3 and 6 of this Standard. The lowest pile capacity determined from either the pile shaft structural strength using the allowable design stresses from this Standard, or the pile capacity based on soil-rock interface strength analyses including all the factors of safety from this Appendix A, should control the single pile design capacity. These factors of safety relate to structural and soil-pile interface strength. Pile settlement behavior must also be considered. Acceptance of lower global factors of safety may increase settlement magnitude of pile foundations.

23

COMMENTARY

Appendix A Partial Factors of Safety

A.3 Commentary A method of partial factors of safety allows the use of a global factor of safety more appropriately reflecting the uncertainties in pile foundation design and construction than a single uniform factor of safety. This method allows for revisions to the usual arbitrary factors of safety when specific criteria are met. These criteria are: (1) pile load tests taken to failure; (2) dynamic measurements coupled with wave equation analysis; (3) static analysis from reliable subsurface information; (4) full time inspection under the direction of the Engineer; (5) integrity testing performed in conjunction with full-time inspection under the direction of the Engineer; and (6) an understanding that, under some conditions, use of lower global factors of safety may increase settlement magnitude of pile foundations. A.3.1 Factor F, Considerations integrated into partial safety factor F, are: (1) variability of subsurface conditions across the site; (2) the quality and reliability of the soil strength data used to estimate the pile capacity, as well as knowledge of soil setup or relaxation with time; (3) the longevity of the structure (temporary, normal service, monument, etc.); (4) environmental effects; and (5) confidence in the magnitude of the loads. The five factors presented have all been combined and presented as one numerical value in Table A. 1 with the specific capacity determination method noted. The following discussion is presented as 24

guidance for gauging when a factor F, must be adjusted from the values shown in Table A.I. The variability of the subsurface conditions across the site is a complex issue, embodying the concepts of stratigraphic continuity, and strength continuity within each particular stratum, the occurrence of obstructions that will prevent installation of a pile to a desired level, and the level at which rock or other unyielding materials are encountered that constitute a very high degree of end-bearing capacity. In considering whether F, may require adjustment, emphasis should be given to the qualitative assessment of strata continuity and soil strength within each stratum, particularly if the pile under consideration is a friction pile. Sites where subsurface and/or published geologic information indicate channel deposits, rapid facies changes, faults, formational contacts, and the like, represent a greater risk of at least some percentage of the piles encountering dramatically different subsurface conditions than have been likely assumed in the pile design. Furthermore, the occurrence of potential obstructions, both from geologic conditions and manmade fill, must be considered. Values in Table A. 1 assume that only modest or predictable variability is expected in the subsurface conditions based upon geologic literature review, a subsurface exploration consistent with good geotechnical engineering practice, and knowledge of subsurface conditions and/or pile installation on adjacent sites. If the exploration indicates highly variable subsurface conditions, only a marginal exploration was performed, geologic literature review indicates formational contacts beneath the site, and so on, then F, should be increased accordingly. Note that the assessment of variability must include all facets of the pile design, namely, lateral, uplift, negative skin friction, and compressive capacity. For example, if the primary design consideration for a pile or pile group is uplift capacity, obstructions or the occurrence of shallow competent rock could have a severe impact on the uplift capacity of the piles. Also, changes in near-surface soil conditions could significantly affect the lateral capacity of piles and pile groups even though deeper subsurface conditions are uniform and provide reasonably consistent uplift and/or compressive capacity. The quality and reliability of the soil strength data embody issues such as the type of test used to obtain or estimate soil strength and the method or manner in which the test was performed. The standard penetration test has been considered the "standard method" assumed in arriving at estimates of

COMMENTARY

strength. Although the standard penetration test can rightly be considered crude and only an index to the strength determined by laboratory or in situ means, it has nonetheless provided a considerable backlog of empirical data and has been the basis for numerous static pile capacity analysis techniques. Some of the primary concerns in evaluating the reliability and quality of standard penetration test results are the type of hammer used (i.e., safety, automatic, donut, pin) and an assessment of the boring techniques used in sandy materials sampled and tested below the water table. The proliferation of hollowstem augers and their frequent use without regard to the subsurface conditions encountered are a significant concern. Another consideration is whether the standard penetration resistances have been obtained using a rope and cathead or have been obtained with one of the currently available automatic hammers. Site-specific adjustment factors should be employed to relate automatic hammer standard penetration resistances to databases obtained with a rope and cathead system. Other techniques, such as use of an electronic cone penetrometer, unconfined compressive strength testing of clays, vane shear testing, borehole shear testing, and use of a dilatometer are all considered superior methods of assessing in-place strength when compared to the standard penetration test. A prior history of instrumented piles in the area often provides information on changes of the pile's capacity due to soil setup or relaxation. If, in the opinion of the Engineer, this information is considered consistent and reliable, it can be used in the static analysis. The factor F, can be reduced accordingly, provided there is local experience with these techniques for the specific pile type and subsurface conditions under consideration. However, F! should be no lower than 1.5. The longevity of the structure affects the magnitude of F,. "Normal" service has been assumed in the formulation of F,. Certainly a temporary structure can reasonably have an F, adjusted lower, whereas a monumental structure, such as the Golden Gate Bridge, the Washington Monument, and the like, reasonably should have an F, adjusted upward, however, again no lower than 1.5.

Environmental effects include degradation of the pile material with time, potential effects of freeze-thaw, and exposure of the pile after construction by physical forces such as scour. The factor F, assumes that the soil chemistry is compatible with the pile type selected and there is reasonable confidence in the stability and permanency of the materials that support the pile shaft. If these normal confidence levels are problematic, the factor F, should be increased accordingly. Confidence in the magnitude of the applied loads primarily deals with the confidence in predicting the live load component that must be supported by the piles. Compilation of factor F, assumes reasonable prediction of such live load components as wind, snow, and seismic forces. Code determination of these loads is considered "normal" confidence.

A.3.2 Factor F2 Considerations integrated into the partial safety factor F2 include: (1) (2) (3) (4)

the pile type; the installation means; construction surveillance; and shaft integrity verification.

Review of Table A.2 indicates that two of the four previously discussed factors (pile type and construction surveillance) can be identified. Integrity verification is not included in this version of the table. Integrity verification is a rapidly evolving field, with current techniques constantly undergoing refinement and new techniques being developed. For example, in the case of pipe piles, a broad definition of integrity testing would involve lowering an inclinometer probe into the pile to determine that there is acceptable curvature prior to concrete placement. The fact that any kind of integrity testing provides additional scrutiny under the direction of the Engineer implies a higher degree of confidence in the pile. The partial safety factor shown in Table A.2 can be reduced if integrity verification tests are used, but in no case should factor F2 be less than 1.0.

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Index Accepted engineering practice 1 ACI standards 20 Adhesional resistance 6 Adjacent property 3 Administrative requirements 3-4 Allowable stresses 9, 10, 11 Allowable structural movement 7 American Wood Preservers Association Standards 9, 20 Anvil 1 ASTM standards 6, 7, 9, 10, 17, 1 8-20 Atmospheric corrosion 3 Auger torques, minimum 4 Auger types, effects 1 2 Auger withdrawal 4, 16, 18 Augered cast-in-place piles 1 8 Augered pressure grouted piles 1, 10, 13, 15, 16 Augering 16 Augering equipment 15 Axial alignment tolerances 13 Axial compression 9, 10, 21 Axial compressive stress 9-10 Bearing capacity 17, 1 8 Bent piles 1 8 Block. See Hammer cushion Borehole shear testing 25 Bracing 4, 14 Building codes 4, 8 Building official 1 Caisson piles 11 Capacity 1, 2, 6, 14 Caps 14 Cast-in-place concrete 1,17 Cast-in-place concrete piles 7', 10, 16 Cohesive resistance 5 Cohesive shear loads 5 Cohesive soils 8 Collapsed piles 1 8 Composite pile connectors 14 Composite pile types 11 Compression 7 Compression tests 7-8 Compressive capacity 6 Compressive piles 6 Compressive strength, concrete 9 Concrete piles 7-8, 9-10. See a/so Cast-in-place concrete piles Concrete-filled shell piles 10 Construction load testing 21 Construction surveillance 25 Continuous driving 1 6 Critical shaft section 5 Cross-sectional area 13

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Current experience 1 Cushion system. See Pile-hammer cushion system Cut-off elevation 1,4, 13 Cyclic action 6 Dead load 8 Design analysis 3 Design capacity 6 Design load 1, 2, 7, 8-9,21 Design modifications 4 Design stress 1, 9-1 2 Dewatering 4, 6 Diesel hammers 15-16 Differential movement 14 Differential settlement 14 Dilatometers 25 Displacement piles 6 Documentation 3, 4, 9, 15, 18 Dog-legged piles 1 8 Drive cap 1 Drive head 1 Driven caisson-type piles 11 Driving anomalies 17 Driving equipment 5, 1 8 Driving resistance 4, 1 8 Driving stresses 5, 1 2-13 Driving system 15 Driving, continuous 16 Durability 3 Dynamic analysis 2, 6, 21 Dynamic field measurements 9 Dynamic measurement and analysis 2, 3, 6, 24 Dynamic measurements 24 Dynamic testing 6, 21 Earth materials 3, 4 Earth pressure 8 Earthquake loads 8 Eccentricity, loads due to 8 Elastic wave equation analysis 12-13 Electronic cone penetrometer 25 End-bearing capacity 6 Engineer 1, 2 Enlarged base piles 10 Environmental effects 21, 24, 25 Established methods of analysis. See Accepted practice

Excavation 3-4, 6 Existing piles, use of 3 Expanding soils 8 Exposure 3 Extruded concrete bases 10 Fabricated piles 10-11 Failure 2 Failure load 2

Field conditions, design modifications Fill 8 Flange projections 10-11 Flange thickness 1 1 Followers 2, 15 Foundation design 21 Foundation investigation 3 Freeze 2 Freeze-thaw cycles 3 Frictional resistance 5, 6

13

Geotechnical capacity 23 Geotechnical engineer 2, 3, 7 Global factors of safety 24 Gross elastic compression 7 Grout pump capacities, effects 12 Grout pumps 15 Hammers 15-16, 18 Hammer cushion 2, 15. See a/so Pile-hammer cushion system Hammer energies 4, 12 Hammer types, effects 1 2 Handling stresses 5 Hard strata 1 3 Heaved piles 16 Helmet 1 High-risk construction environment 21 High-strain dynamic test 6 Hydrostatic uplift 8 Ice 8 Impact hammers 15 Indicator piles 1 8 Installation anomalies 17 Installation criteria 4 Installation equipment 15 Installation methods 6, 14, 25 Installation records 1 8 Installation sequence 12, 13-14, 16-17

Jetting, effects 1 2, 1 6 Lateral capacity analysis 6 Lateral design capacity 6 Lateral loads 3, 5, 6, 8 Laterally supported embedded foundation piles 9 Level readings 16 Load tests 2, 4, 6-8, 24 Loads, maximum combination of 8 Location 13 Longevity of structure 25 Longitudinally fluted steel tube piles 11 Low strain pile dynamic testing 6 Mandrel-driven shell piles 1 1 Marine construction 9

Maximum allowable shaft stresses 5, 9-12 Maximum driving stresses 13 Maximum transient loads 21 Mini-piles 2, 12 Minimum global factors of safety 22 Mixing equipment 15 Negative friction 2, 5, 6, 8 Obstructions 13, 17 One-dimensional wave equation 15 Operations 15-16 Other work, coordination with 3-4 Overburden 8 Partial safety factors, minimum values 21 Penetration lengths 4 Penetration measurements 1 8 Penetration rates 4 Pile cushion 2, 15. See a/so Pile-hammer cushion system Pile groups 5-6, 8-9, 14 Pile length 5, 6, 12; differences in 17 Pile location 4 Pile movement under load 6 Pile protection 17 Pile setup 2, 17 Pile shaft. See Shaft Pile structural integrity 6 Pile types, multiple 14 Pile-hammer cushion system 12, 16 Pile-soil interaction 6 Pipe piles 10, 11, 16 Plans and specifications 4. See a/so Documentation Post-tensioned concrete slabs 14 Pre-drilling, effects 1 2 Pre-excavation 16 Precast concrete bases 10 Precast reinforced concrete base elements 10 Preservative treatment, timber piles 9 Prestressed precast concrete piles 9-10 Probe piles 1 8 Pumping equipment 15 Pumping rates, minimum 4 Records 4, 18. See a/so Documentation Reinforced concrete slabs 14 Reinforced precast concrete piles 9 Reinforcing steel 9 Relaxation 17 Rolled steel H piles, minimum dimensions 10-1 1 Safety factors 21 -25 Scour 3, 6 Sea water exposure 3 Seismic activity 6 Seismic design 14

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Seismic loads 8 Service load 2, 8 Settlement 2 Shaft, damage to 13; integrity verification 25; material requirements, minimum 4; overstressing 3; strength of 3, 4-5 Shear resistance 5 Shell piles 16 Shoring 4 Slope stabilization 4 Soil conditions 4 Soil freeze 16, 1 7 Soil strength 6, 21, 24 Soil strength properties 6 Soil-pile capacity, analysis of 5, 6 Soil-pile interface 4, 21, 23 Spacing 5-6, 8, 13-14 Splices 14 Spudding 16 Standard penetration test 24-25 Static analysis 2, 6, 21, 24 Static load tests 6, 7-8 Static resistance analysis 6 Steel piles 8, 10-12 Steel pipe 10; concrete filled 11 Steel shells 10 Structural sections, nominal depth 11 Structural steel shafts 1 0 Structural strength 4-5 Subsurface conditions 21,24 Subsurface exploration 6 Subsurface foundation investigation 3, 9 Supporting strata 2, 5-6 Surcharge 6, 8 Swelling 8 Tensile capacity 6 Testing records 1 8 Tests to failure 6, 24 Thermal stresses 3 Timber piles 7, 9, 10, 13 Time-dependent pile-soil strength constraints 7, 17 Tip, damage to 13; elevation 4, 16, 18; movement 8; reinforcement 17 Top-driven open-ended piles 11 Tube piles 1 1 , 1 6 Ultimate capacity 5 Ultimate load 1, 2 Uncased cast-in-place concrete piles 10, 1 3 Uncased shell piles 16 Unconfined compressive testing of clays 25 Unsupported length 3, 5 Uplift capacity 7, 8 Uplift loads 7, 8 U.S. Army Corps of Engineers CE CRD-C79 17

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Vane shear testing 25 Vibratory hammers 15 Water pressure 8 Water table fluctuations 6 Wave action 6, 8 Wave equation analysis 2, 9, 24 Web thickness 11 Welded steel piles 10 Wet-rotary drilling 16 Wind 8 Working load 2