1、Designation: D 2845 05Standard Test Method forLaboratory Determination of Pulse Velocities and UltrasonicElastic Constants of Rock1This standard is issued under the fixed designation D 2845; the number immediately following the designation indicates the year oforiginal adoption or, in the case of re
2、vision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This test method describes equipment and proceduresfor laboratory measurements of the pulse velo
3、cities of com-pression waves and shear waves in rock (1)2and the determi-nation of ultrasonic elastic constants (Note 1) of an isotropicrock or one exhibiting slight anisotropy.NOTE 1The elastic constants determined by this test method aretermed ultrasonic since the pulse frequencies used are above
4、the audiblerange. The terms sonic and dynamic are sometimes applied to theseconstants but do not describe them precisely (2). It is possible that theultrasonic elastic constants may differ from those determined by otherdynamic methods.1.2 This test method is valid for wave velocity measure-ments in
5、both anisotropic and isotropic rocks although thevelocities obtained in grossly anisotropic rocks may be influ-enced by such factors as direction, travel distance, and diam-eter of transducers.1.3 The ultrasonic elastic constants are calculated from themeasured wave velocities and the bulk density.
6、The limitingdegree of anisotropy for which calculations of elastic constantsare allowed and procedures for determining the degree ofanisotropy are specified.1.4 The values stated in inch-pounds are to be regarded asthe standard. The SI values given in parenthesis are providedfor information purposes
7、 only.1.5 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 regulatory limitations prior to use.2. Refere
8、nced Documents2.1 ASTM Standards:3D 653 Terminology Relating to Rock, Soil, and ContainedFluidsD 2216 Test Method for Laboratory Determination of Water(Moisture) Content of Soil and Rock by MassD 3740 Practice for Minimum Requirements for AgenciesEngaged in the Testing and/or Inspection of Soil and
9、Rockas Used in Engineering Design and ConstructionD 6026 Practice for Using Significant Digits in Geotechni-cal DataE 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3. Terminology3.1 For common definitions of terms in this standard, referto Terminology
10、 D 653.3.2 Definitions of Terms Specific to This Standard:3.2.1 compression wave velocitythe dilational wave ve-locity which is the propagation velocity of a longitudinal wavein a medium that is effectively infinite in lateral extent. It is notto be confused with bar or rod velocity.4. Summary of Te
11、st Method4.1 Details of essential procedures for the determination ofthe ultrasonic velocity, measured in terms of travel time anddistance, of compression and shear waves in rock specimensinclude requirements of instrumentation, suggested types oftransducers, methods of preparation, and effects of s
12、pecimengeometry and grain size. Elastic constants may be calculatedfor isotropic or slightly anisotropic rocks, while anisotropy isreported in terms of the variation of wave velocity withdirection in the rock.5. Significance and Use5.1 The primary advantages of ultrasonic testing are that ityields c
13、ompression and shear wave velocities, and ultrasonicvalues for the elastic constants of intact homogeneous isotropicrock specimens (3). Elastic constants are not to be calculatedfor rocks having pronounced anisotropy by procedures de-scribed in this test method. The values of elastic constants often
14、do not agree with those determined by static laboratorymethods or the in situ methods. Measured wave velocitieslikewise may not agree with seismic velocities, but offer goodapproximations. The ultrasonic evaluation of rock properties is1This test method is under the jurisdiction ofASTM Committee D18
15、 on Soil andRock and is the direct responsibility of Subcommittee D18.12 on Rock Mechanics.Current edition approved June 1, 2005. Published July 2005. Originally approvedin 1969. Last previous edition approved in 2000 as D 2845 00.2The boldface numbers in parentheses refer to the list of references
16、at the end ofthis test method.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1*A Summary of Changes section
17、appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.useful for preliminary prediction of static properties. The testmethod is useful for evaluating the effects of uniaxial stress andwater saturation on
18、pulse velocity. These properties are in turnuseful in engineering design.5.2 The test method as described herein is not adequate formeasurement of stress-wave attenuation. Also, while pulsevelocities can be employed to determine the elastic constants ofmaterials having a high degree of anisotropy, t
19、hese proceduresare not treated herein.NOTE 2The quality of the result produced by this standard isdependent on the competence of the personnel performing it, and thesuitability of the equipment and facilities used. Agencies that meet thecriteria of Practice D 3740 are generally considered capable of
20、 competentand objective testing and sampling. Users of this standard are cautionedthat compliance with Practice D 3740 does not in itself assure reliableresults. Reliable results depend on many factors; Practice D 3740 providesa means of evaluating some of those factors.6. Apparatus6.1 GeneralThe te
21、sting apparatus (Fig. 1) should haveimpedance matched electronic components and shielded leadsto ensure efficient energy transfer. To prevent damage to theapparatus allowable voltage inputs should not be exceeded.6.2 Pulse Generator UnitThis unit shall consist of anelectronic pulse generator and ext
22、ernal voltage or poweramplifiers if needed. A voltage output in the form of eitherrectangular pulse or a gated sine wave is satisfactory. Thegenerator shall have a voltage output with a maximum valueafter amplification of at least 50 V into a 50-V impedance load.A variable pulse width, with a range
23、of 1 to 10 s is desirable.The pulse repetition rate may be fixed at 60 repetitions persecond or less although a range of 20 to 100 repetitions persecond is recommended. The pulse generator shall also have atrigger-pulse output to trigger the oscilloscope. There shall bea variable delay of the main-p
24、ulse output with respect to thetrigger-pulse output, with a minimum range of 0 to 20 s.6.3 TransducersThe transducers shall consist of a trans-mitter that converts electrical pulses into mechanical pulsesand a receiver that converts mechanical pulses into electricalpulses. Environmental conditions s
25、uch as ambient temperature,moisture, humidity, and impact should be considered in select-ing the transducer element. Piezoelectric elements are usuallyrecommended, but magnetostrictive elements may be suitable.Thickness-expander piezoelectric elements generate and sensepredominately compression-wave
26、 energy; thickness-shear pi-ezoelectric elements are preferred for shear-wave measure-ments. Commonly used piezoelectric materials include ceram-ics such as lead-zirconate-titanate for either compression orshear, and crystals such as a-c cut quartz for shear. To reducescattering and poorly defined f
27、irst arrivals at the receiver, thetransmitter shall be designed to generate wavelengths at least3 3 the average grain size of the rock.NOTE 3Wavelength is the wave velocity in the rock specimen dividedby the resonance frequency of the transducer. Commonly used frequenciesrange from 75 kHz to 3 MHz.6
28、.3.1 In laboratory testing, it may be convenient to useunhoused transducer elements. But if the output voltage of thereceiver is low, the element should be housed in metal(grounded) to reduce stray electromagnetic pickup. If protec-tion from mechanical damage is necessary, the transmitter aswell as
29、the receiver may be housed in metal. This also allowsspecial backings for the transducer element to alter its sensi-tivity or reduce ringing (4). The basic features of a housedelement are illustrated in Fig. 2. Energy transmission betweenthe transducer element and test specimen can be improved by( 1
30、) machining or lapping the surfaces of the face plates tomake them smooth, flat, and parallel, (2) making the face platefrom a metal such as magnesium whose characteristic imped-ance is close to that of common rock types, (3) making the faceplate as thin as practicable, and (4) coupling the transduc
31、erelement to the face plate by a thin layer of an electricallyconductive adhesive, an epoxy type being suggested.6.3.2 Pulse velocities may also be determined for specimenssubjected to uniaxial states of stress. The transducer housingsin this case will also serve as loading platens and should beNOTE
32、 1Components shown by dashed lines are optional, depending on method of travel-time measurement and voltage sensitivity of oscilloscope.FIG. 1 Schematic Diagram of Typical ApparatusD 2845 052designed with thick face plates to assure uniform loading overthe ends of the specimen (5).NOTE 4The state of
33、 stress in many rock types has a marked effect onthe wave velocities. Rocks in situ are usually in a stressed state andtherefore tests under stress have practical significance.6.4 PreamplifierA voltage preamplifier is required if thevoltage output of the receiving transducer is relatively low orif t
34、he display and timing units are relatively insensitive. Topreserve fast rise times, the frequency response of the pream-plifier shall drop no more than 2 dB over a frequency rangefrom 5 kHz to 4 3 the resonance frequency of the receiver. Theinternal noise and gain must also be considered in selectin
35、g apreamplifier. Oscilloscopes having a vertical-signal output canbe used to amplify the signal for an electronic counter.6.5 Display and Timing UnitThe voltage pulse applied tothe transmitting transducer and the voltage output from thereceiving transducer shall be displayed on a cathode-rayoscillos
36、cope for visual observation of the waveforms. Theoscilloscope shall have an essentially flat response between afrequency of 5 kHz and 4 3 the resonance frequency of thetransducers. It shall have dual beams or dual traces so that thetwo waveforms may be displayed simultaneously and theiramplitudes se
37、parately controlled. The oscilloscope shall betriggered by a triggering pulse from the pulse generator. Thetiming unit shall be capable of measuring intervals between 2s and 5 ms to an accuracy of 1 part in 100. Two alternativeclasses of timing units are suggested, the respective positionsof each be
38、ing shown as dotted outlines in the block diagram inFig. 1:(1) an electronic counter with provisions for timeinterval measurements, or (2) a time-delay circuit such as acontinuously variable-delay generator, or a delayed-sweepfeature on the oscilloscope. The travel-time measuring circuitshall be cal
39、ibrated periodically with respect to its accuracy andlinearity over the range of the instrument. The calibration shallbe checked against signals transmitted by the National Instituteof Standards and Technology radio station WWV, or against acrystal controlled time-mark or frequency generator that ca
40、n bereferenced back to the signals from WWV periodically. It isrecommended that the calibration of the time measuring circuitbe checked at least once a month and after any severe impactthat the instrument may receive.7. Test Specimens7.1 PreparationExercise care in core drilling, handling,sawing, gr
41、inding, and lapping the test specimen to minimizethe mechanical damage caused by stress and heat. It isrecommended that liquids other than water be prevented fromcontacting the specimen, except when necessary as a couplingmedium between specimen and transducer during the test. Thesurface area under
42、each transducer shall be sufficiently planethat a feeler gage 0.001 in. (0.025 mm) thick will not passunder a straightedge placed on the surface. The two oppositesurfaces on which the transducers will be placed shall beparallel to within 0.005 in./in. (0.1 mm/20 mm) of lateraldimension (Fig. 3). If
43、the pulse velocity measurements are tobe made along a diameter of a core, the above tolerance thenrefers to the parallelism of the lines of contact between thetransducers and curved surface of the rock core. Moisturecontent of the test specimen can affect the measured pulsevelocities. Pulse velociti
44、es may be determined on the velocitytest specimen for rocks in the oven-dry state (0 % saturation),in a saturated condition (100 % saturation), or in any interme-diate state. If the pulse velocities are to be determined with therock in the same moisture condition as received or as existsunderground,
45、 care must be exercised during the preparationprocedure so that the moisture content does not change. In thiscase it is suggested that both the sample and test specimen bestored in moisture-proof bags or coated with wax and that drysurface-preparation procedures be employed. If results aredesired fo
46、r specimens in the oven-dried condition, refer to TestMethod D 2216. The specimen shall remain submerged inwater up to the time of testing when results are desired for thesaturated state.7.2 Limitation on DimensionsIt is recommended that theratio of the pulse-travel distance to the minimum lateraldi
47、mension not exceed 5. Reliable pulse velocities may not bemeasurable for high values of this ratio. The travel distance ofthe pulse through the rock shall be at least 10 3 the averagegrain size so that an accurate average propagation velocity maybe determined. The grain size of the rock sample, the
48、naturalresonance frequency of the transducers, and the minimumlateral dimension of the specimen are interrelated factors thataffect test results. The wavelength corresponding to the domi-nant frequency of the pulse train in the rock is approximatelyrelated to the natural resonance frequency of the t
49、ransducer andthe pulse-propagation velocity, (compression or shear) asfollows:L V/f, (1)FIG. 2 Basic Features of a Housed Transmitter or ReceiverNOTE 1(A) must be within 0.1 mm of (B) for each 20 mm of width(C).FIG. 3 Specification for ParallelismD 2845 053where:L = dominant wavelength of pulse train, in. (or m),V = pulse propagation velocity (compression or shear),in./s (or m/s), andf = natural resonance frequency of transducers, Hz.The minimum lateral dimension of the test specimen shall beat least 5 3 the wavelength of the compression wave so thatthe true dilat
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