ASTM D4945-2017 Standard Test Method for High-Strain Dynamic Testing of Deep Foundations《深基础高应变动态测试的标准试验方法》.pdf

《ASTM D4945-2017 Standard Test Method for High-Strain Dynamic Testing of Deep Foundations《深基础高应变动态测试的标准试验方法》.pdf》由会员分享，可在线阅读，更多相关《ASTM D4945-2017 Standard Test Method for High-Strain Dynamic Testing of Deep Foundations《深基础高应变动态测试的标准试验方法》.pdf（14页珍藏版）》请在麦多课文档分享上搜索。

1、Designation: D4945 12D4945 17Standard Test Method forHigh-Strain Dynamic Testing of Deep Foundations1This standard is issued under the fixed designation D4945; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revisi

2、on. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope Scope*1.1 This dynamic test method covers the procedure for applying an axial impact force with a pile driving hammer or a largedrop

3、 weight that will cause a relatively high strain at the top of an individual vertical or inclined deep foundation unit, and formeasuring the subsequent force and velocity response of that deep foundation unit. While in this standard force and velocity arereferenced as “measured,” they are typically

4、derived from measured strain and acceleration values. High-strain dynamic testingapplies to any deep foundation unit, also referred to herein as a “pile,” which functions in a manner similar to a driven pile or acast-in-place pile regardless of the method of installation, and which conforms with the

5、 requirements of this test method.1.2 This standard provides minimum requirements for dynamic testing of deep foundations. Plans, specifications, or provisions(or combinations thereof) prepared by a qualified engineer may provide additional requirements and procedures as needed tosatisfy the objecti

6、ves of a particular test program. The engineer in responsible charge of the foundation design, referred to hereinas the “Engineer”, shall approve any deviations, deletions, or additions to the requirements of this standard.1.3 The proper conduct and evaluation of high-strain dynamic tests requires s

7、pecial knowledge and experience. A qualifiedengineer should directly supervise the acquisition of field data and the interpretation of the test results so as to predict the actualperformance and adequacy of deep foundations used in the constructed foundation.Aqualified engineer shall approve the app

8、aratusused for applying the impact force, driving appurtenances, test rigging, hoist equipment, support frames, templates, and testprocedures.1.4 The text of this standard references notes and footnotes which provide explanatory material. These notes and footnotes(excluding those in tables and figur

9、es) shall not be considered as requirements of the standard. The word “shall” indicates amandatory provision, and the word “should” indicates a recommended or advisory provision. Imperative sentences indicatemandatory provisions.1.5 UnitsThe values stated in SI units are to be regarded as standard.

10、No other units of measurement are included in thisstandard. Reporting of test results in units other than SI shall not be regarded as nonconformance with this test method.1.6 All observed and calculated values shall conform to the guidelines for significant digits and rounding established in Practic

11、eD6026.1.6.1 The procedures used to specify how data are collected/recorded and calculated in this standard are regarded as the industrystandard. In addition, they are representative of the significant digits that should generally be retained. The procedures used do notconsider material variation, p

12、urpose for obtaining the data, special purpose studies, or any considerations for the users objectives;and it is common practice to increase or reduce significant digits of reported data to commensurate with these considerations. Itis beyond the scope of this standard to consider significant digits

13、used in analysis methods for engineering design.1.7 The method used to specify how data are collected, calculated, or recorded in this standard is not directly related to theaccuracy to which the data can be applied in design or other uses, or both. How one applies the results obtained using this st

14、andardis beyond its scope.1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine theapplicability o

15、f regulatory limitations prior to use. For a specific precautionary statement, see Note 4.1.8 This international standard was developed in accordance with internationally recognized principles on standardizationestablished in the Decision on Principles for the Development of International Standards,

16、 Guides and Recommendations issuedby the World Trade Organization Technical Barriers to Trade (TBT) Committee.1 This test method is under the jurisdiction of ASTM Committee D18 on Soil and Rock and is the direct responsibility of Subcommittee D18.11 on Deep Foundations.Current edition approved May 1

17、, 2012Nov. 1, 2017. Published June 2012December 2017. Originally approved in 1989. Last previous edition approved in 20082012 asD4945 08.D4945 12. DOI: 10.1520/D4945-12.10.1520/D4945-17.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication o

18、f what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considere

19、d the official document.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States12. Referenced Documents2.1 ASTM Standards:2C469 Test Method for Static Modulus of Elasticity and

20、Poissons Ratio of Concrete in CompressionD198 Test Methods of Static Tests of Lumber in Structural SizesD653 Terminology Relating to Soil, Rock, and Contained FluidsD1143/D1143M Test Methods for Deep Foundations Under Static Axial Compressive LoadD3689 Test Methods for Deep Foundations Under Static

21、Axial Tensile LoadD3740 Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used inEngineering Design and ConstructionD6026 Practice for Using Significant Digits in Geotechnical Data3. Terminology3.1 DefinitionsDefinitions: For common definitions o

22、f terms used in this standard, see Terminology D653.3.1.1 For definitions of common technical terms in this standard, refer to Terminology D653.3.2 Definitions of Terms Specific to This Standard:3.2.1 cast in-place pile, na deep foundation unit made of cement grout or concrete and constructed in its

23、 final location, forexample, drilled shafts, bored piles, caissons, auger cast piles, pressure-injected footings, etc.3.2.2 deep foundation, na relatively slender structural element that transmits some or all of the load it supports to the soil orrock well below the ground surface, that is, a driven

24、 pile, a cast-in-place pile, or an alternate structural element having a similarfunction.3.2.3 deep foundation cushion, nthe material inserted between the helmet on top of the deep foundation and the deepfoundation (usually plywood).3.2.4 deep foundation impedance, na measure of the deep foundations

25、 resistance to motion when subjected to an impactevent. Deep foundation impedance can be calculated by multiplying the cross-sectional area by the dynamic modulus of elasticityand dividing the product by the wave speed. Alternatively, the impedance can be calculated by multiplying the mass density b

26、ythe wave speed and cross-sectional area.Z 5EA/c! 5cA (1)where:Z = impedance,E = dynamic modulus of elasticity,A = cross-sectional area,c = wave speed, and = mass density.3.2.4.1 DiscussionDeep foundation impedance can be estimated by multiplying the cross-sectional area by the dynamic modulus of el

27、asticity anddividing the product by the wave speed.Alternatively, the impedance can be estimated by multiplying the mass density by the wavespeed and cross-sectional area.Z 5EA/c! 5cA (1)where:Z = impedance,E = dynamic modulus of elasticity,A = pile cross-sectional area,c = wave speed, and = mass de

28、nsity.3.2.5 driven pile, na deep foundation unit made of preformed material with a predetermined shape and size and typicallyinstalled by impact hammering, vibrating, or pushing.3.2.6 follower, na structural section placed between the impact device and the deep foundation during installation or test

29、ing.3.2.7 hammer cushion, nthe material inserted between the hammer striker plate and the helmet on top of the deep foundation.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information,

30、 refer to the standards Document Summary page on the ASTM website.D4945 1723.2.8 impact event, nthe period of time during which the deep foundation is moving due to the impact force application. SeeFig. 1.3.2.9 impact force, nin the case of strain transducers,the transient the impact force is obtain

31、ed by multiplying the measuredstrain () with the cross-sectional area (force applied to the topA) and the dynamic modulus of elasticity (of the deepE foundation).element.3.2.10 mandrel, na stiff structural member placed inside a thin shell to allow impact installation of the thin section shell.3.2.1

32、1 moment of impact, nthe first time after the start of the impact event when the acceleration is zero. See Fig. 1.3.2.12 particle velocity, nthe instantaneous velocity of a particle in the deep foundation as a strain wave passes by.3.2.13 restrike, n or vthe redriving of a previously driven pile, ty

33、pically after a waiting period of 15 min to 30 days or more,to assess changes in ultimate axial compressive static capacity during the time elapsed after the initial installation.3.2.14 wave speed, nthe speed with which a strain wave propagates through a deep foundation. It is a property of the deep

34、foundation composition and for one-dimensional wave propagation is equal to the square root of the quotient of the Modulus ofElasticity divided by mass density: c = (E/) 1/2.3.2.14.1 DiscussionThe wave speed is a property of the deep foundation composition and for one-dimensional wave propagation is

35、 equal to the squareroot of the quotient of the Modulus of Elasticity divided by mass density: c = (E/)1/2. For wood and concrete piles, the wave speedis the average wave speed over the pile length.4. Significance and Use4.1 Based on the measurements from strain or force, and acceleration, velocity,

36、 or displacement transducers, this This testmethod obtains the force and velocity induced in a pile during an axial impact event (see Figs. 1 and 2). Force and velocity aretypically derived from measured strain and acceleration. The Engineer may analyze the acquired data using engineering principles

37、and judgment to evaluate the integrity of the pile, the performance of the impact system, and the maximum compressive and tensilestresses occurring in the pile.4.2 If sufficient axial movement occurs during the impact event, and after assessing the resulting dynamic soil response alongthe side and b

38、ottom of the pile, the Engineer may analyze the results of a high-strain dynamic test to estimate the ultimate axialstatic compression capacity (see Note 1). Factors that may affect the axial static capacity estimated from dynamic tests include,but are not limited to the: (1) pile installation equip

39、ment and procedures, (2) elapsed time since initial installation, (3) pile materialproperties and dimensions, (4) type, density, strength, stratification, and saturation of the soil, or rock, or both adjacent to andbeneath the pile, (5) quality or type of dynamic test data, (6) foundation settlement

40、, (7) analysis method, and (8) engineeringjudgment and experience. If the Engineer does not have adequate previous experience with these factors, and with the analysis ofFIG. 1 Typical Force and Velocity Traces Generated by the Apparatus for Obtaining Dynamic MeasurementsD4945 173dynamic test data,

41、then a static load test carried out according to Test Method D1143/D1143M should be used to verify estimatesof static capacity and its distribution along the pile length. Test Method D1143/D1143M provides a direct and more reliablemeasurement of static capacity.(1) pile installation equipment and pr

42、ocedures,(2) elapsed time since initial installation,(3) pile material properties and dimensions,(4) type, density, strength, stratification, and saturation of the soil, or rock, or both adjacent to and beneath the pile,(5) quality or type of dynamic test data,(6) foundation settlement,(7) analysis

43、method, and(8) engineering judgment and experience.If the Engineer does not have adequate previous experience with these factors, and with the analysis of dynamic test data, thena static load test carried out according to Test Method D1143/D1143M should be used to verify estimates of static capacity

44、 andits distribution along the pile length. Test Method D1143/D1143M provides a direct and more reliable measurement of staticcapacity.NOTE 1The analysis of a dynamic test will under predict the ultimate axial static compression capacity if the pile movement during the impact eventis too small. The

45、Engineer should determine how the size and shape of the pile, and the properties of the soil or rock beneath and adjacent to the pile,affect the amount of movement required to fully mobilize the static capacity. A permanent net penetration of as little as 2 mm per impact may indicatethat sufficient

46、movement has occurred during the impact event to fully mobilize the capacity. However, high displacement driven piles may require greatermovement to avoid under predicting the static capacity, and cast-in-place piles often require a larger cumulative permanent net penetration for a seriesof test blo

47、ws to fully mobilize the capacity. Static capacity may also decrease or increase over time after the pile installation, and both static and dynamictests represent the capacity at the time of the respective test. Correlations between measured ultimate axial static compression capacity and dynamic tes

48、testimates generally improve when using dynamic restrike tests that account for soil strength changes with time (see 6.8).NOTE 2Although interpretation of the dynamic test analysis may provide an estimate of the piles tension (uplift) capacity, users of this standard arecautioned to interpret conser

49、vatively the side resistance estimated from analysis of a single dynamic measurement location, and to avoid tension capacityestimates altogether for piles with less than 10 m embedded length. (Additional transducers embedded near the pile toe may also help improve tensioncapacity estimates.) If the Engineer does not have adequate previous experience for the specific site and pile type with the analysis of dynamic test datafor tension capacity, then a static load test carried out according to Test Method D3689 should be used to verify tension ca