1、Designation: D 4428/D 4428M 07Standard Test Methods forCrosshole Seismic Testing1This standard is issued under the fixed designation D 4428/D 4428M; the number immediately following the designation indicates theyear of original adoption or, in the case of revision, the year of last revision. A numbe
2、r in parentheses indicates the year of lastreapproval. A superscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope*1.1 These test methods are limited to the determination ofhorizontally traveling compression (P) and shear (S) seismicwaves at test sites cons
3、isting primarily of soil materials (asopposed to rock). A preferred test method intended for use oncritical projects where the highest quality data must be ob-tained is included. Also included is an optional methodintended for use on projects which do not require measure-ments of a high degree of pr
4、ecision.1.2 Various applications of the data will be addressed andacceptable interpretation procedures and equipment, such asseismic sources, receivers, and recording systems will bediscussed. Other items addressed include borehole spacing,drilling, casing, grouting, deviation surveys, and actual te
5、stconduct. Data reduction and interpretation is limited to theidentification of various seismic wave types, apparent velocityrelation to true velocity, example computations, effectiveborehole spacing, use of Snells law of refraction, assumptions,and computer programs.1.3 It is important to note that
6、 more than one acceptabledevice can be used to generate a high-quality P wave or Swave, or both. Further, several types of commercially availablereceivers and recording systems can also be used to conduct anacceptable crosshole survey. Consequently, these test methodsprimarily concern the actual tes
7、t procedure, data interpretation,and specifications for equipment which will yield uniform testresults.1.4 All recorded and calculated values shall conform to theguide for significant digits and rounding established in PracticeD 6026.1.4.1 The procedures used to specify how data are collected/record
8、ed 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 material variation, purpose forobtaining the data, special purpose studies, or any consi
9、der-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 consider significant digits used inanalysis methods for engineering design.1.4.2 Measure
10、ments made to more significant digits orbetter sensitivity than specified in these test methods shall notbe regarded a nonconformance with this standard.1.5 These test methods are written using SI units. Inch-pound units are provided for convenience. The values stated ininch pound units may not be e
11、xact equivalents; therefore, theyshall be used independently of the SI system. Combiningvalues from the two systems may result in nonconformancewith these test methods.1.5.1 The gravitational system of inch-pound units is usedwhen dealing with inch-pound units. In this system, the pound(lbf) represe
12、nts 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 It is common practice in the engineering/constructionprofession to concurrently use pounds to represent both a unitof mass (lbm) and of force
13、 (lbf). This implicitly combines twoseparate systems of units; that is, the absolute system and thegravitational system. It is scientifically undesirable to combinethe use of two separate sets of inch-pound units within a singlestandard.As stated, these test methods include the gravitationalsystem o
14、f inch-pound units and do not use or present the slugunit for mass. However, the use of balances 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, i
15、f 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. Referenced Documents2.1 ASTM Standards:D 653 Terminology Relating to Soil, Rock, and C
16、ontainedFluidsD 3740 Practice for Minimum Requirements for AgenciesEngaged in the Testing and/or Inspection of Soil and Rockas Used in Engineering Design and Construction1These test methods are under the jurisdiction ofASTM Committee D18 on Soiland Rock and are the direct responsibility of Subcommit
17、tee D18.09 on Cyclic andDynamic Properties of Soils.Current edition approved July 1, 2007. Published August 2007. Originallyapproved in 1984. Last previous edition approved in 2000 as D 4428/D 4428M 00.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 1
18、00 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.D 6026 Practice for Using Significant Digits in Geotechni-cal Data3. Terminology3.1 Definitions: For definitions of other terms used in theseTest Methods, see Terminology D 653.4. Summary of Test Method4.1 The Crossho
19、le Seismic Test makes direct measurementsof compression velocities, shear wave velocities, or both, inboreholes advanced through soil or rock. At selected depthsdown the borehole, a borehole seismic source is used togenerate a seismic wave train. Downhole receivers are used todetect the arrival of t
20、he seismic wave train in offset borings.Cased borings that are spaced 10 to 20 ft apart are typicallyused. The distance between boreholes at the test depths ismeasured using a borehole deviation survey. The boreholeseismic source is connected to and triggers a data recordingsystem that records the r
21、esponse of the downhole receiver(s),thus measuring the travel time of the wave train between thesource and receiver(s). The compression or shear wave veloc-ity is calculated from the measured distance and travel time forthe respective wave train.NOTE 1The quality of the results produced by these tes
22、t methods isdependent on the competence of the personnel performing it and thesuitability of the equipment and facilities. Agencies that meet the criteriaof Practice D 3740 are generally considered capable of competent andobjective testing/sampling/inspection and so forth. Users of these testmethods
23、 are cautioned that compliance with Practice D 3740 does not initself assure reliable results. Reliable results depend on many factors;Practice D 3740 provides a means of evaluating some of those factors.5. Significance and Use5.1 The seismic crosshole method provides a designer withinformation pert
24、inent to the seismic wave velocities of thematerials in question (1).2This data may be used as input intostatic/dynamic analyses, as a means for computing shearmodulus, Youngs modulus, and Poissons ratio, or simply forthe determination of anomalies that might exist betweenboreholes.5.2 Fundamental a
25、ssumptions inherent in the test methodsare as follows:5.2.1 Horizontal layering is assumed.5.2.2 Snells laws of refraction will apply. If Snells laws ofrefraction are not applied, velocities obtained will be unreli-able.6. Apparatus6.1 The basic data acquisition system consists of the fol-lowing:6.1
26、.1 Energy SourcesThese energy sources are chosenaccording to the needs of the survey, the primary considerationbeing 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 transmi
27、t adequate energy to the medium incompression or volume change. Impulsive sources, such asexplosives, hammers, or air guns, are all acceptable P-wavegenerators. To produce an identifiable S wave, the sourceshould transmit energy to the ground primarily by directional-ized distortion. For good S wave
28、s, energy sources must berepeatable and, although not mandatory, reversible. TheS-wave source must be capable of producing an S-wave trainwith an amplitude at least twice that of the P-wave train. Fig.1 and Fig. 2 show examples of impulse and vibratory seismicsources.6.1.2 ReceiversThe receivers int
29、ended for use in thecrosshole test shall be transducers having appropriate fre-quency and sensitivity characteristics to determine the seismicwave train arrival. Typical examples include geophones andaccelerometers. The frequency response of the transducer mustnot vary more than 5 % over a range of
30、frequencies from12 to2 times the predominant frequency of the site-specific S-wavetrain. Each receiving unit will consist of at least three trans-ducers combined orthogonally to form a triaxial array, that is,one vertical and two horizontal transducers mounted at rightangles, one to the other. In th
31、is triaxis arrangement, only thevertical component will be acceptable for S-wave arrivaldeterminations. In cases where P-wave arrivals are not desired,a uniaxial vertical transducer may be used. P-wave arrivals willbe determined using the horizontal transducer oriented mostnearly radially to the sou
32、rce. The transducer(s) shall be housedin a single container (cylindrical shape preferred) not exceed-ing 450 mm 18 in. in length. Provision must be made for thecontainer to be held in firm contact with the sidewall of theborehole. Examples of acceptable methods include: air bladder,wedge, stiff spri
33、ng, or mechanical expander.6.1.3 Recording System The system shall consist of sepa-rate amplifiers, one for each transducer being recorded, havingidentical phase characteristics and adjustable gain control.Only digital signal filtering will be acceptable.Analog filtering,active or passive, will not
34、be acceptable because of inherentphase delays. The receiver signals shall be displayed in amanner such that precision timing of the P and S-wave arrivalreferenced to the instant of seismic source activation can be2The boldface numbers in parentheses refer to the list of references at the end ofthis
35、standard.FIG. 1 Reversible Impulse Seismic Source (Produces Both P andS Wave Trains)D 4428/D 4428M 072determined within 0.1 ms when materials other than rock arebeing tested. Timing accuracy shall be demonstrated bothimmediately prior to and immediately after the conduct of thecrosshole test. Demons
36、trate accuracy by inducing and record-ing on the receiver channels an oscillating signal of 1000 Hzderived from a quartz-controlled oscillator, or, a certifiedlaboratory calibration obtained within the time frame recom-mended by the instrument manufacturer. Further, the timingsignal shall be recorde
37、d at every sweep rate or recorder speed,or both, used during conduct of the crosshole test. As anoptional method, the true zero time shall be determined by (1)a simultaneous display of the triggering mechanism along withat least one receiver, or (2) a laboratory calibration (accurate to0.1 ms) of th
38、e triggering mechanism which will determine thelapsed time between the trigger closure and development ofthat voltage required to initiate the sweep on an oscilloscope orseismograph. Permanent records of the seismic events shall bemade by either scope-mounted camera or oscillograph.7. Procedure7.1 B
39、orehole Preparation:7.1.1 PreferredThe preferred method for preparing aborehole set for crosshole testing incorporates three boreholesin line, spaced 3.0 m 10 ft apart, center-to-center on theground surface, as illustrated in Fig. 3. If, however, it is knownthat S wave velocities will exceed 450 m/s
40、 1500 ft/s, such asis often encountered in alluvial materials, borehole spacingsmay be extended to 4.5 m 15 ft.7.1.1.1 Drill the boreholes, with minimum sidewall distur-bance, to a diameter not exceeding 175 mm 7.0 in. After thedrilling is completed, case the borings with 50 to 100 mm 2 to4 in. insi
41、de diameter PVC pipe or aluminum casing, takinginto consideration the size of the borehole source and down-hole receivers. Before inserting the casing, close the bottom ofthe pipe with a cap which has a one way ball-check valvecapable of accommodating 38 mm 112 in. outside diametergrout pipe. Center
42、 the casing with spacers and insert it into thebottom of the borehole. Grout the casing in place by (1)inserting a 38 mm 112 in. PVC pipe through the center of thecasing, contacting the one-way valve fixed to the end cap (Fig.4 (sideA), or (2) by a small diameter grout tube inserted to thebottom of
43、the borehole between the casing and the boreholesidewall (Fig. 4 (side B).Another acceptable method would beto fill the borehole with grout which would be displaced byend-capped fluid-filled casing. The grout mixture should beformulated to approximate closely the density of the surround-ing in situ
44、material after solidification. That portion of theboring that penetrates rock should be grouted with a conven-tional portland cement which will harden to a density of about2.20 Mg/m3140 lb/ft3. That portion of the boring in contactwith soils, sands, or gravels should be grouted with a mixturesimulat
45、ing the average density of the medium (about 1.80 to1.90 Mg/m3110 to 120 lb/ft3) by premixing 450 g 1 lb ofbentonite and 450 g 1 lb of portland cement to 2.80 kg 6.25lb of water. Anchor the casing and pump the grout using aconventional, circulating pump capable of moving the groutthrough the grout p
46、ipe to the bottom of the casing upward fromthe bottom of the borehole (Fig. 4). Using this procedure, theannular space between the sidewall of the borehole and thecasing will be filled from bottom to top in a uniform fashiondisplacing mud and debris with minimum sidewall disturbance.Keep the casing
47、anchored and allow the grout to set beforeusing the boreholes for crosshole testing. If shrinkage occursnear the mouth of the borehole, additional grout should beinserted until the annular space is filled flush with the groundsurface (4).7.1.2 OptionalIf the scope or intended use of a particularproj
48、ect does not warrant the time and expense which would beincurred by the preferred method, or if the specific project suchas an investigation beneath a relatively small machine founda-tion is undertaken, this optional method may be used.7.1.2.1 In all cases, a minimum of two boreholes must beused. If
49、 the borings are to be 15 m 50 ft deep or less,verticality will be controlled using a level on the drill stemextending into the borehole. Center-to-center surface boreholespacing will be determined by the nature of the project.Borings may be used either with or without casing; however, ifcasing is used, grout must be injected between the casing andsidewall of the borehole to ensure good contact in the mannerdescribed in 7.1.1.1. If the center-to-center surface boreholespacing exceeds 6.0 m 20 ft, the probability of measurementof refracted
