1、Designation: D7400/D7400M 19Standard Test Methods forDownhole Seismic Testing1This standard is issued under the fixed designation D7400/D7400M; the number immediately following the designation indicates theyear of original adoption or, in the case of revision, the year of last revision. A number in
2、parentheses indicates the year of lastreapproval. A superscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 These test methods address compression (P) and shear(S) waves propagating in the downward direction in a nearlyvertical plane. The seismic waves
3、 can be denoted as PVor PZfor a downward propagating compression wave and as SVHorSZXfor downward propagating and horizontally polarizedshear wave. The SVHor SZXis also referred to as an SHwave.These test methods are limited to the determination of theinterval velocities from arrival times and relat
4、ive arrival timesof compression (P) waves and vertically (SV) and horizontally(SH) oriented shear (S) seismic waves which are generatednear surface and travel down to an array of vertically installedseismic sensors. Two methods are discussed, which includeusing either one or two downhole sensors (re
5、ceivers).1.2 Various applications of the data will be addressed andacceptable procedures and equipment, such as seismic sources,receivers, and recording systems will be discussed. Other itemsaddressed include source-to-receiver spacing, drilling, casing,grouting, a procedure for borehole installatio
6、n, and conductingactual borehole and seismic cone tests. Data reduction andinterpretation is limited to the identification of various seismicwave types, apparent velocity relation to true velocity, examplecomputations, use of Snells law of refraction, and assump-tions.1.3 There are several acceptabl
7、e devices that can be used togenerate a high-quality P or SV source wave or both and SHsource waves. Several types of commercially available receiv-ers and recording systems can also be used to conduct anacceptable downhole survey. Special consideration should begiven to the types of receivers used
8、and their configuration toprovide an output that accurately reflects the input motion.These test methods primarily concern the actual test procedure,data interpretation, and specifications for equipment which willyield uniform test results.1.4 All recorded and calculated values shall conform to theg
9、uide for significant digits and rounding established in PracticeD6026.1.4.1 The procedures used to specify how data are collected/recorded and calculated in these test methods are regarded asthe industry standard. In addition, they are representative of thesignificant digits that should generally be
10、 retained. The proce-dures used do not consider material variation, purpose forobtaining the data, special purpose studies, or any consider-ations for the users objectives; and it is common practice toincrease or reduce significant digits of reported data to becommensurate with these considerations.
11、 It is beyond the scopeof these test methods to consider significant digits used inanalysis methods for engineering design.1.4.2 Measurements made to more significant digits orbetter sensitivity than specified in these test methods shall notbe regarded a nonconformance with this standard.1.5 UnitsTh
12、e values stated in either SI units or inch-pound units are to be regarded separately as standard. Thevalues stated in each system may not be exact equivalents;therefore, each system shall be used independently of the other.Combining values from the two systems may result in non-conformance with the
13、standard.1.5.1 The gravitational system of inch-pound units is usedwhen dealing with inch-pound units. In this system, the pound(lbf) represents a unit of force (weight), while the unit for massis slugs. The rationalized slug unit is not given, unless dynamic(F = ma) calculations are involved.1.5.2
14、It is common practice in the engineering/constructionprofession to concurrently use pounds to represent both a unitof mass (lbm) and of force (lbf). This implicitly combines twoseparate systems of units; that is, the absolute system and thegravitational system. It is scientifically undesirable to co
15、mbinethe use of two separate sets of inch-pound units within a singlestandard. As stated, this standard includes the gravitationalsystem of inch-pound units and does not use/present the slugunit for mass. However, the use of balances or scales recordingpounds of mass (lbm) or recording density in lb
16、m/ft3shall notbe regarded as nonconformance with this standard.1.6 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, health, and environmental practices and dete
17、r-mine the applicability of regulatory limitations prior to use.1This test method is under the jurisdiction ofASTM Committee D18 on Soil andRock and is the direct responsibility of Subcommittee D18.09 on Cyclic andDynamic Properties of Soils.Current edition approved Feb. 1, 2019. Published February
18、2019. Originallyapproved in 2007. Last previous edition approved in 2017 as D7400 17. DOI:10.1520/D7400_D7400M-19.*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 StatesThis int
19、ernational standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) C
20、ommittee.11.7 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalB
21、arriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D653 Terminology Relating to Soil, Rock, and ContainedFluidsD3740 Practice for Minimum Requirements for AgenciesEngaged in Testing and/or Inspection of Soil and Rock asUsed in Engineering Design and ConstructionD4428/D4428M
22、Test Methods for Crosshole Seismic Test-ingD5778 Test Method for Electronic Friction Cone and Piezo-cone Penetration Testing of SoilsD6026 Practice for Using Significant Digits in GeotechnicalData3. Terminology3.1 Definitions:3.1.1 For definitions of common technical terms in thisstandard, refer to
23、Terminology D653.3.2 Definitions of Terms Specific to This Standard:3.2.1 seismic wave trainthe recorded motion of a seismicdisturbance with time.4. Summary of Test Method4.1 The Downhole Seismic Test makes direct measurementsof compression (P-) or shear (S-) wave velocities, or both, in aborehole a
24、dvanced through soil or rock or in a cone penetrationtest sounding. It is similar in several respects to the CrossholeSeismic Test Method (Test Methods D4428/D4428M). Aseismic source is used to generate a seismic wave train at theground surface offset horizontally from the top of a casedborehole. Do
25、wnhole receivers are used to detect the arrival ofthe seismic wave train. The downhole receiver(s) may bepositioned at selected test depths in a borehole or advanced aspart of the instrumentation package on an electronic conepenetrometer (Test Method D5778). The seismic source isconnected to and tri
26、ggers a data recording system that recordsthe response of the downhole receiver(s), thus measuring thetravel time of the wave train between the source and receiv-er(s). Measurements of the arrival times (travel time fromsource to sensor) of the generated P- and S- waves are thenmade so that the low
27、strain (104%) in-situ P-wave andS-wave velocities can be determined. The calculated seismicvelocities are used to characterize the natural or man-made (orboth) properties of the stratigraphic profile.5. Significance and Use5.1 The seismic downhole method provides a designer withinformation pertinent
28、 to the seismic wave velocities of thematerials in question (1)3. The P-wave and S-wave velocitiesare directly related to the important geotechnical elastic con-stants of Poissons ratio, shear modulus, bulk modulus, andYoungs modulus. Accurate in-situ P-wave and S-wave veloc-ity profiles are essenti
29、al in geotechnical foundation designs.These parameters are used in both analyses of soil behaviorunder both static and dynamic loads where the elastic constantsare input variables into the models defining the different statesof deformations such as elastic, elasto-plastic, and failure.Another import
30、ant use of estimated shear wave velocities ingeotechnical design is in the liquefaction assessment of soils.5.2 A fundamental assumption inherent in the test methodsis that a laterally homogeneous medium is being characterized.In a laterally homogeneous medium the source wave traintrajectories adher
31、e to Snells law of refraction. Another as-sumption inherent in the test methods is that the stratigraphicmedium to be characterized can have transverse isotropy.Transverse isotropy is a particularly simple form of anisotropybecause velocities only vary with vertical incidence angle andnot with azimu
32、th. By placing and actuating the seismic sourceat offsets rotated 90 in plan view, it may be possible to confirmthat a more complex model is needed to evaluate the field data.5.3 In soft saturated soil, where the P-wave velocity of thesoil is less than the P-wave velocity of water, which is about145
33、0 m/s 4750 ft/s, the P-wave velocity measurement willprimarily be controlled by the P-wave velocity of water and adirect measurement of the soil P-wave velocity will not bepossible.NOTE 1The quality of the results produced by this standard isdependent on the competence of the personnel performing it
34、, and thesuitability of the equipment and facilities. Agencies that meet the criteriaof Practice D3740 are generally considered capable of competent andobjective testing/sampling/inspection/etc. Users of this standard are cau-tioned that compliance with Practice D3740 does not in itself assurereliab
35、le results. Reliable results depend on many factors; Practice D3740provides a means of evaluating some of those factors.6. Apparatus6.1 The basic data acquisition system consists of the fol-lowing:6.1.1 Energy SourcesThese energy sources are chosenaccording to the needs of the survey, the primary co
36、nsiderationbeing whether P-wave or S-wave velocities are to be deter-mined. The source should be rich in the type of energyrequired, that is, to produce good P-wave data, the energysource must transmit adequate energy to the medium incompression or volume change. Impulsive sources, such asexplosives
37、, hammers, or air guns, are all acceptable P-wavegenerators. To produce an identifiable S wave, the sourceshould transmit energy to the ground with a particle motionperpendicular or transverse to the axis of the survey. Impulse orvibratory S-wave sources are acceptable, but the source mustbe repeata
38、ble and, although not mandatory, reversible.2For 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.3The boldface num
39、bers in parentheses refer to a list of references at the end ofthis standard.D7400/D7400M 1926.1.1.1 Shear BeamAshear beam is a common form of anSH-wave energy source (2). The beam can be metal or wood,and may be encased at the ends and bottom with a steel plate.Strike plates may optionally be provi
40、ded at the beam ends. Thebottom plate may optionally have cleats to penetrate the groundand to prevent sliding when struck. A commonly utilized shearbeam has approximate dimensions of 2.4 m 8 ft long by 150mm 6 in. wide. The center of the shear beam is placed on theground at a horizontal offset rang
41、ing from 1 to4m3to12ftfrom the receiver borehole (or cone insertion point). Thishorizontal offset should be selected carefully since boreholedisturbance, rod noise, and refraction through layers withsignificantly different properties may impact the test results.Larger horizontal offsets of 4 to 6 m
42、12 to 20 ft for theseismic source may be necessary to avoid response effects dueto surface or near-surface features. In this case the possibilityof raypath refraction must be taken into account. The ends ofthe beam should be positioned equidistant from the receiverborehole. The shear beam is typical
43、ly then loaded by the axleload of vehicle wheels or the leveling jacks of the cone rig. Theground should be level enough to provide good continuouscontact along the whole length of the beam to ensure goodcoupling between the beam and the ground. Beam-to-groundcoupling should be accomplished by scrap
44、ing the ground levelto a smooth, intact surface. Backfilling to create a flat spot willnot provide good beam-ground coupling and should beavoided. The shear beam is typically struck on a strike plate atone end using a nominal 1- to 15-kg 2- to 33-lb hammer toproduce a seismic wave train. Striking th
45、e other end will createa seismic wave train that has the opposite polarity relative tothe wave train produced at the first end. Fig. 1 shows a diagramof the typical shear beam configuration that will produceSH-wave trains. Fig. 2 shows an example of an impulseseismic source wave train that contains
46、both P- and S-wavecomponents. Although the shear beam of dimensions 2.4 m 8ft long by 150 mm 6 in. wide is commonly utilized, it maybe desirable to implement beams of shorter length so thatSH-source more closely approximates a “point source” for testsless than 20 m 60 ft in depth. The “point source”
47、 SH-wavebeam allows for the accurate specification of the sourceCartesian location (x, y, and z coordinates) which is requiredfor the subsequent interval velocity calculation. For example, ifa large SH-hammer beam is utilized, it becomes difficult tospecify the exact location of the seismic source.
48、In addition, itis preferable to initially excite a small area if complexstratigraphy exist and shorter SH-hammer beams mitigateproblems arising from poor beam-ground coupling.NOTE 2The ranges of dimensions and hammer units shown in Fig. 1are examples of typical energy source configurations but are n
49、ot the onlymeans to produce acceptable seismic wave trains. In this typical case,heavier hammers and longer pivot arms will generally produce higherenergy wave trains and deeper penetration into the soil and rock as longas ground coupling with the shear beam is maintained.6.1.2 ReceiversIn the downhole seismic test, the seismicreceivers are installed vertically with depth within a boreholeor as part of the instrumentation in a cone penetrometer probe.The receivers intended for use in the downhole test shall beFIG. 1 Typical Downhole Shear Wave Source
