1、Designation: D4428/D4428M 14Standard Test Methods forCrosshole Seismic Testing1This standard is issued under the fixed designation D4428/D4428M; 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 are limited to the determination ofthe velocity of two types of horizontally travelling seismicwaves in soil materials; prim
3、ary compression (P-wave) andsecondary shear (S-wave) waves. The standard assumes thatthe method used to analyze the data obtained is based on firstarrival times or interval arrival times over a measured distance.1.2 Acceptable interpretation procedures and equipment,such as seismic sources, receiver
4、s, and recording systems arediscussed. Other items addressed include borehole spacing,drilling, casing, grouting, deviation surveys, and actual testprocedures.1.3 These test methods are primarily concerned with theactual test procedure, data interpretation, and specifications forequipment which will
5、 yield uniform test results.1.4 All recorded and calculated values shall conform to theguide 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
6、. The procedures used do not considermaterial variation, purpose for obtaining the data, specialpurpose studies, or any considerations for the users objectives.Measurements made to more significant digits or better sensi-tivity than specified in these test methods shall not be regardeda nonconforman
7、ce with this standard.1.5 UnitsThe values stated in either SI units or inch-pound units presented in brackets are to be regarded sepa-rately as standard. The values stated in each system may not beexact equivalents; therefore, each system shall be used inde-pendently of the other. Combining values f
8、rom the two systemsmay result in non-conformance with the standard. Reporting oftest results in units other than SI shall not be regarded asnonconformance with this test method.1.6 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsi
9、bility 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:D653 Terminology Relating to Soil, Rock, and ContainedFluidsD3740 Practice for Minimum Requireme
10、nts for AgenciesEngaged in Testing and/or Inspection of Soil and Rock asUsed in Engineering Design and ConstructionD6026 Practice for Using Significant Digits in GeotechnicalData3. Terminology3.1 Definitions:3.1.1 For definitions of common technical terms in thisstandard, refer to Terminology D653.3
11、.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 Crosshole Seismic Test makes direct measurementsof P-wave velocities, or S-wave velocities, in boreholes ad-vanced primarily through soil.
12、At selected depths down theborehole, a borehole seismic source is used to generate aseismic wave train. Downhole receivers are used to detect thearrival of the seismic wave train in offset borings at arecommended spacing of 3 to 6 m 10 to 20 ft. The distancebetween boreholes at the test depths is me
13、asured using aborehole deviation survey. The borehole seismic source isconnected to and triggers a data recording system that recordsthe response of the downhole receivers, thus measuring thetravel time of the wave train between the source and receivers.1These test methods are under the jurisdiction
14、 of ASTM Committee D18 on Soiland Rock and are the direct responsibility of Subcommittee D18.09 on Cyclic andDynamic Properties of Soils.Current edition approved March 1, 2014. Published April 2014. Originallyapproved in 1984. Last previous edition approved in 2007 as D4428/D4428M 07.DOI: 10.1520/D4
15、428_D4428M-14.*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 States1The P-wave or S-wave velocity is calculated from the mea-sured distance and travel time for the respective
16、wave train.5. Significance and Use5.1 The seismic crosshole method provides a designer withinformation pertinent to the seismic wave velocities of thematerials in question (1).2This data may be used as follows:5.1.1 For input into static/dynamic analyses;5.1.2 For computing shear modulus, Youngs mod
17、ulus, andPoissons ratio (provided density is known or assumed);5.1.3 For determining Seismic Site Class using the appro-priate Building Code; and5.1.4 For assessing liquefaction potential.5.2 Fundamental assumptions inherent in the test methodsare as follows:5.2.1 Horizontal layering is assumed.5.2.
18、2 Snells law of refraction applies to P-waves andS-waves and to the velocities derived from crosshole tests. IfSnells law of refraction is not considered in the analysis ofCrosshole seismic testing data, the report shall so state, and theP-wave and S-wave velocities obtained may be unreliable forcer
19、tain depth intervals near changes in stratigraphy (2).NOTE 1The quality of the results produced by these test methods isdependent on the competence of the personnel performing it and thesuitability of the equipment and facilities. Agencies that meet the criteriaof Practice D3740 are generally consid
20、ered capable of competent andobjective testing/sampling/inspection and so forth. Users of these testmethods are cautioned that compliance with Practice D3740 does not initself assure reliable results. Reliable results depend on many factors;Practice D3740 provides a means of evaluating some of those
21、 factors.6. Apparatus6.1 The basic data acquisition system consists of the fol-lowing:6.1.1 Energy SourcesThe source shall be rich in the typeof energy required, that is, to produce good P-wave data, theenergy source must transmit adequate energy to the medium incompression or volume change. Impulsi
22、ve sources, such asexplosives, hammers, or air guns, are all acceptable P-wavegenerators. To produce an identifiable S-wave, the source shalltransmit energy to the ground primarily by distortion. Verti-cally polarized S-waves (SV) are most commonly measured,but horizontally polarized S-waves are als
23、o very useful. Fig. 1and Fig. 2 show examples of impulse and vibratory seismicsource wave trains respectively. For good S-waves, energysources must be repeatable and, although not mandatory,reversible. The S-wave source must be capable of producing anS-wave train with an amplitude greater than the P
24、-wave train.6.1.2 ReceiversThe receivers intended for use in thecrosshole test shall be transducers having appropriate fre-quency and sensitivity characteristics to determine the seismicwave train arrivals. Typical examples include geophones andaccelerometers. S-waves are typically in the range of 5
25、0 to 500Hz depending on the soil properties and signal source mecha-nism while P-waves may be as high as 2000 Hz. It is importantthat the receivers have a flat response over this range offrequencies. This can be accomplished by using geophoneswith a resonance at or below 10 Hz or accelerometers with
26、 aresonance at or above 10 000 Hz. It is important that allreceivers used in the testing be of the same type and withmatched characteristics. Each receiving unit will normallyconsist of three receivers combined orthogonally to form atriaxial array, that is, one vertical and two horizontal receivers2
27、The boldface numbers in parentheses refer to the list of references at the end ofthis standard.FIG. 1 Reversible Impulse Seismic Source Time Plot Showing Both P-Wave and S-Wave TrainsD4428/D4428M 142mounted at right angles, one to the other. In this triaxialarrangement, only the vertical component w
28、ill be acceptablefor determining the arrival of an SV-wave (S-wave in thevertical plane). Horizontally oriented receivers must be usedfor determining the arrival of an SH-wave (S-wave in thehorizontal plane). The P-wave may be detected by any of thethree components. The one oriented radially will pr
29、ovide thebest sensitivity. Provision must be made for the receivers(s) tobe held in firm contact with the sidewall of the borehole orcasing. Examples of acceptable methods include: air bladder,wedge, stiff spring, or mechanical expander.6.1.3 Recording System:6.1.3.1 The system shall consist of sepa
30、rate recordingchannels, one for each receiver being recorded, having at least12 bits of resolution. The timing accuracy of all instrumentsthat are used in the travel time measurements shall be cali-brated traceable to an appropriate government standardsagency. Time scale accuracy may be demonstrated
31、 by inducingand recording an oscillating square wave signal of 1000 Hzderived from a calibrated quartz-controlled oscillator. Timingshall be to a resolution of 0.1 msec. Timing accuracy shall bedemonstrated for all time scales used during the conduct of thetests.6.1.3.2 Raw data shall be recorded di
32、rectly without filteringexcept for the application of anti-aliasing filters which are setbetween 0.3 to 0.4 times the sampling frequency. Filtering orother post processing must pay attention to possible timeshifting or distortion of the seismic wave train arrivals.6.1.3.3 When velocities are determi
33、ned using the travel timebetween a source (S) and two receivers (R1 and R2), thesignals shall be recorded in a manner such that precision timingof the P- and S-wave arrival referenced to the instant of seismicsource activation can be determined within 0.1 ms. Forexample, a seismic in-hole source and
34、 two receivers could berecorded multiple times to demonstrate accurate and consistenttriggering by comparing the velocities determined for S-R1 andS-R2 with R1-R2 paths. When only two boreholes are used andvelocities are determined by time interval S-R1, documentationof the trigger accuracy relative
35、 to the instant of seismic sourcegeneration must be provided. When velocities are determinedusing only the time interval between R1 and R2 and asimultaneous recording of R1 and R2, the trigger time is notneeded.6.1.3.4 Permanent records shall be made of the seismicevents to allow for subsequent revi
36、ew and analysis of the data.7. Procedure7.1 Borehole Preparation:7.1.1 The recommended layout for crosshole testing incor-porates three or more boreholes in line although two boreholesmay be used. Three holes provide a level of redundancy notprovided with two holes. Use of only two holes will be inc
37、ompliance with this procedure if trigger accuracy is demon-strated and documented (6.1.3.3). Borehole spacing must bemeasured to a resolution of 60.02 m. Borehole azimuth mustbe measured to a resolution of 61 degrees of a designatedreference direction. Borehole elevations must be measured to aprecis
38、ion of 60.1 m. Spacing between the source borehole andthe first receiver borehole shall be 1.5 to3m5to10ftandthe distance between subsequent receiver boreholes shall be 3to 6 m l0 to 20 ft apart. A typical layout is illustrated in Fig.3. For two boreholes, spacing between the source borehole andthe
39、receiver borehole shall be 1.5 to5m5to15ft.7.1.1.1 Borings with CasingIf casing is used to house thereceivers it shall be grouted in place. Drill the boreholes, withminimum sidewall disturbance, to a diameter no greater thanrequired to perform the test. After the drilling is completed,case the borin
40、gs with 50 to 100 mm 2 to 4 in. inside diameterPVC pipe or aluminum casing, taking into consideration thesize of the borehole source and downhole receivers. Beforeinserting the casing, close the bottom of the casing pipe with acap which has a one way ball-check valve capable of accom-modating 38 mm
41、112 in. outside diameter grout pipe. If atremie pipe is used for the grouting, a ball check valve is notneeded. Insert the casing down to the bottom of the borehole.Grout the casing in place by (1) inserting a 38 mm 112 in.PVC pipe through the center of the casing, contacting theone-way valve fixed
42、to the end cap (Fig. 4 (left side), or (2)bya small diameter grout tube inserted to the bottom of theborehole between the casing and the borehole sidewall (Fig. 4(right side). Another acceptable method would be to fill theborehole with grout which would be displaced by end-cappedfluid-filled casing.
43、 The grout mixture shall be formulated toapproximate closely the unit weight of the surrounding in situmaterial after solidification. That portion of the boring thatpenetrates rock shall be grouted with ordinary portland cementFIG. 2 Borehole Vibratory Seismic Source Time Plot (Produces S-Wave Train
44、 Only)D4428/D4428M 143which will harden to a unit weight of about 22 kN/m3unitweight of 140 lb/ft3. That portion of the boring in contact withsoils, sands, or gravels shall be grouted with a mixturesimulating the average unit weight of the medium (about 18 to19 kN/m3110 to 120 lb/ft3) by premixing 4
45、.4 N 1 lb ofbentonite and 4.4 N 1 lb of portland cement to 27N 6.25 lbof water. Anchor the casing and pump the grout using aconventional, circulating pump capable of moving the groutthrough the grout pipe to the bottom of the casing and upwardfrom the bottom of the borehole (Fig. 4). Using this proc
46、edure,the annular 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 anchored and allow the grout to set beforedeviation measurement or crosshole testing is perform
47、ed. Thisgrout mix will not set hard but will become a “rigid“ gel. Ifshrinkage occurs near the mouth of the borehole, additionalgrout shall be inserted until the annular space is filled flushwith the ground surface (3).7.1.1.2 Borings without CasingIn some situations thesurvey may be performed witho
48、ut casing in the receiver holes.The receivers must be held in firm contact with the sidewall ofthe borehole during the measurements. The Borehole Devia-tion Survey (7.2) may be conducted with casing (if necessary)temporarily installed without being grouted in place.7.2 Borehole Deviation SurveyA bor
49、ehole deviation sur-vey must be conducted in order to accurately determine thespacing at the elevations of the seismic tests.7.2.1 Conduct a borehole deviation survey in all crossholeborings with an instrument capable of measuring the precisevertical alignment of each hole. The instrument must have thecapability of determining tilt with a sensitivity of 0.3. Infor-mation thus obtained will enable the investigator to computeNOTE 1Spacing may vary with site conditions.FIG. 3 Typical Crosshole Seismic TestD4428/D4428M 144the horizontal pos
