ASTM D4945-2000 Standard Test Method for High-Strain Dynamic Testing of Piles《桩的高应力动态试验的标准试验方法》.pdf
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1、Designation: D 4945 00Standard Test Method forHigh-Strain Dynamic Testing of Piles1This standard is issued under the fixed designation D 4945; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in p
2、arentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the procedure for testing verti-cal or batter piles individually to determine the force andvelocity response of the pile
3、to an impact force applied axiallyby a pile driving hammer or similar device that will cause alarge strain impact to the top of the pile. This test method isapplicable to deep foundation units that function in a mannersimilar to foundation piles, regardless of their method ofinstallation provided th
4、at they are receptive to high strainimpact testing.1.2 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of
5、regulatory limitations prior to use. For a specificprecautionary statement, see Note 5.NOTE 1High-strain dynamic testing requires a strain at impact whichis representative of a force in the pile having the same order of magnitude,or greater, than the ultimate capacity of the pile.NOTE 2This standard
6、 method may be applied for high-strain dynamictesting of piles with the use of only force or strain transducers and/oracceleration, velocity or displacement transducers as long as the testresults clearly state how the testing deviates from the standard.NOTE 3A suitable follower may be required for t
7、esting cast-in-placeconcrete piles. This follower should have an impedance between 80 and150 % of that of the pile. However, additional caution and analysis may berequired if the impedance is not within 10 %. For mandrel-driven piles,the mandrel may be instrumented in a similar way to a driven pilep
8、rovided that the mandrel is constructed of a single member with nojoints.2. Referenced Documents2.1 ASTM Standards:C 469 Test Method for Static Modulus of Elasticity andPoissons Ratio of Concrete in Compression2D 198 Methods of Static Tests of Timbers in StructuralSizes3D 653 Terminology Relating to
9、 Soil, Rock, and ContainedFluids4D 1143 Test Method for Piles Under Static Axial Compres-sive Load43. Terminology3.1 Except as defined in 3.2, the terminology used in thistest method conforms with Terminology D 653.3.2 Definitions of Terms Specific to This Standard:3.2.1 capblockthe material inserte
10、d between the hammerstriker plate and the drive cap on top of the pile (also calledhammer cushion).3.2.2 cushionthe material inserted between the drive capon top of the pile and the pile (also called pile cushion).3.2.3 impact eventthe period of time during which thepile is moving in a positive and/
11、or negative direction ofpenetration due to the impact force application. See Fig. 1.3.2.4 moment of impactthe first moment of time after thestart of the impact event when the acceleration is zero. See Fig.1.3.2.5 pile impedanceindicates the resistance a pile has toa sudden impact change in velocity.
12、3.2.5.1 DiscussionIt can be calculated by multiplying thecross-sectional area by Youngs Modulus of Elasticity anddividing the product by the strain wave speed. Alternatively,the impedance can be calculated by multiplying the unitspecific density by the wave speed and cross-sectional area.Z 5 AE/c 5r
13、CA (1)where:Z = Impedance,A = Cross-sectional area,E = Youngs Modulus of Elasticity,C = Wave speed of pile, andr = Unit specific density.3.2.6 strain wave speed (or wave speed)the speed withwhich a strain wave propagates through a pile; it is a propertyof the pile composition.3.2.7 particle velocity
14、the instantaneous velocity of a par-ticle in the pile as a strain wave passes by.3.2.8 restrikingthe redriving of a previously driven pileafter a waiting period of from 15 min to 30 days or more.3.2.8.1 DiscussionThe length of the waiting period isdependent upon the type of pile and the soil conditi
15、ons alongthe shaft and at the toe of the pile.1This test method is under the jurisdiction of ASTM Committee D18 on Soil andRock and is the direct responsibility of Subcommittee D18.11 on Deep Foundations.Current edition approved Nov. 10, 2000. Published November 2000. Originallypublished as D 4945 8
16、9. Last previous edition D 4945 96.2Annual Book of ASTM Standards, Vol 04.02.3Annual Book of ASTM Standards, Vol 04.10.4Annual Book of ASTM Standards, Vol 04.08.1Copyright ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.4. Significance and Use4.1 This test method is used
17、 to provide data on strain orforce and acceleration, velocity or displacement of a pile underimpact force. The data are used to estimate the bearing capacityand the integrity of the pile, as well as hammer performance,pile stresses, and soil dynamics characteristics, such as soildamping coefficients
18、 and quake values. This test method is notintended to replace Test Method D 1143.5. Apparatus5.1 Apparatus for Applying Impact Force:5.1.1 Impact Force ApplicationAny conventional piledriving hammer or similar device is acceptable for applying theimpact force provided it is capable of generating a n
19、etmeasurable pile penetration, or an estimated mobilized staticresistance in the bearing strata which, for a minimum period of3 ms, exceeds to a sufficient degree the working load assignedto the pile, as judged by the engineer in charge. The deviceshall be positioned so that the impact is applied ax
20、ially to thehead of the pile and concentric with the pile.5.2 Apparatus for Obtaining Dynamic MeasurementsTheapparatus shall include transducers, which are capable ofindependently measuring strain and acceleration versus time ata specific location along the pile axis during the impact event.A minimu
21、m of two of each of these devices, one of each onopposing sides of the pile, shall be securely attached so thatthey do not slip. Bolt-on, glue-on, or weld-on transducers areacceptable.5.2.1 Force or Strain TransducersThe strain transducersshall have a linear output over the entire range of possibles
22、trains. When attached to the pile, their natural frequency shallbe in excess of 2000 Hz. The measured strain shall beconverted to force using the pile cross-section area anddynamic modulus of elasticity at the measured location. Thedynamic modulus of elasticity may be assumed to be 200 to207 3 106kP
23、a (29 to 30 3 106psi) for steel. The dynamicmodulus of elasticity for concrete and wood piles may beestimated by measurement during the compression test inaccordance with Test Method C 469 and Methods D 198.Alternatively, the modulus of elasticity for concrete, wood, andsteel piles can be calculated
24、 from the square of the wave speed(determined as indicated in 6.2) times the specific unit density( E =pc2).5.2.1.1 Force measurements also are made by force trans-ducers placed between the pile head and the driving hammer,although it should be recognized that such a transducer iscapable of altering
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