1、Designation: D7400 17Standard Test Methods forDownhole Seismic Testing1This standard is issued under the fixed designation D7400; 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 parentheses in
2、dicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 These test methods are limited to the determination ofthe interval velocities from arrival times and relative arrivaltimes of compression (P) waves and vertic
3、ally (SV) andhorizontally (SH) oriented shear (S) seismic waves which aregenerated near surface and travel down to an array of verticallyinstalled seismic sensors. Two methods are discussed, whichinclude using either one or two downhole sensors (receivers).1.2 Various applications of the data will b
4、e 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 installation, and conductingactual borehole and seismic cone te
5、sts. 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 acceptable devices that can be used togenerate a high-quality
6、 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 and their configuration toprovide an output that acc
7、urately 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 theguide for significant digits and rounding established
8、 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 retained. The proce-dures used do not consider mate
9、rial 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. It is beyond the scopeof these test methods to cons
10、ider 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 The values stated in either SI units or inch-pound units(gi
11、ven in brackets) are to be regarded separately as standard.The values 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 standard. Reporting of test results in
12、units other than SI shall not be regarded as non-conformancewith this 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
13、 is not given, unless dynamic(F = ma) calculations are involved.1.5.2 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 syst
14、em and thegravitational system. It is scientifically undesirable to combinethe 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 balan
15、ces or scales recordingpounds of mass (lbm) or recording density in lbm/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 estab
16、lish appro-priate safety, health, and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.7 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles
17、for the1This 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 Nov. 1, 2017. Published December 2017. Originallyapproved in 2007. Last previous edition a
18、pproved in 2014 as D7400 14. DOI:10.1520/D7400-17.*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 international standard was developed in accordance with internation
19、ally 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) Committee.1Development of International Standards, Guides and Rec
20、om-mendations issued by the World Trade Organization TechnicalBarriers 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
21、Rock asUsed in Engineering Design and ConstructionD4428/D4428M 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 d
22、efinitions of common technical terms in thisstandard, refer to Terminology D653.3.2 Definitions of Terms Specific to This Standard:3.2.1 seismic wave trainthe recorded motion of a seismicdisturbance with time.3.2.2 shear waveA seismic wave in which the disturbanceis an elastic deformation perpendicu
23、lar to the direction ofmotion of the wave.3.2.3 shear wave velocitythe speed (velocity) of a shearwave through soil or rock.4. Summary of Test Method4.1 The Downhole Seismic Test makes direct measurementsof compression (P-) or shear (S-) wave velocities, or both, in aborehole advanced through soil o
24、r 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. Downhole receivers are u
25、sed 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 triggers a data recording
26、 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 strain (104%) in-situ
27、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 to the seismic wave v
28、elocities 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 essential in geotechnical fou
29、ndation 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 important use of estimated s
30、hear 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 adhere to Snells law of ref
31、raction. 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 azimuth. By placing and act
32、uating the seismic sourceat offsets rotated 90 in plan view, it may be possible toevaluate the transverse anisotropy of the medium.5.3 In soft saturated soil, where the P-wave velocity of thesoil is less than the P-wave velocity of water, which is about1450 m/s 4750 ft/s, the P-wave velocity measure
33、ment will becontrolled by the P-wave velocity of water and a directmeasurement of the soil P-wave velocity will not be possible.NOTE 1The quality of the results produced by this standard isdependent on the competence of the personnel performing it, and thesuitability of the equipment and facilities.
34、 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 assurereliable results. Reliable results depend on many factors;
35、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 considerationbeing whether P-wave or S-wave velocities
36、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, hammers, or air guns, are all acceptable P-wavegene
37、rators. 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 repeatable and, although not mandatory, reversible.2For refe
38、renced 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 numbers in parentheses refer to a list of references at
39、the end ofthis standard.D7400 1726.1.1.1 Shear BeamA shear 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 provided at the beam ends. Thebottom plate may optionally have c
40、leats 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 ranging from 1 to4m3to12ftfrom the receiver borehole (or cone i
41、nsertion 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 12 to 20 ft for theseismic source may be necessary to avoid
42、 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 typically then loaded by the axleload of vehicle wheels or the lev
43、eling 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 scraping the ground levelto a smooth, intact surface. Backfillin
44、g 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 the other end will createa seismic wave train that has the op
45、posite 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 both P- and S-wavecomponents. Although the shear beam of di
46、mensions 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” SH-wavebeam allows for the accurate specification of the s
47、ourceCartesian 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. In addition, itis preferable to initially excite a small ar
48、ea 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 not the onlymeans to produce acceptable seismic wave trains.
49、 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 (Produces SH- Wave Train)D7400 173transducers having app
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