ASTM D4428/D4428M-00
(Test Method)Standard Test Methods for Crosshole Seismic Testing
Standard Test Methods for Crosshole Seismic Testing
SCOPE
1.1 These test methods are limited to the determination of horizontally traveling compression (P) and shear (S) seismic waves at test sites consisting primarily of soil materials (as opposed to rock). A preferred test method intended for use on critical projects where the highest quality data must be obtained is included. Also included is an optional method intended for use on projects which do not require measurements of a high degree of precision.
1.2 Various applications of the data will be addressed and acceptable interpretation procedures and equipment, such as seismic sources, receivers, and recording systems will be discussed. Other items addressed include borehole spacing, drilling, casing, grouting, deviation surveys, and actual test conduct. Data reduction and interpretation is limited to the identification of various seismic wave types, apparent velocity relation to true velocity, example computations, effective borehole spacing, use of Snell's law of refraction, assumptions, and computer programs.
1.3 It is important to note that more than one acceptable device can be used to generate a high-quality P wave or S wave, or both. Further, several types of commercially available receivers and recording systems can also be used to conduct an acceptable crosshole survey. Consequently, these test methods primarily concern the actual test procedure, data interpretation, and specifications for equipment which will yield uniform test results.
1.4 The values stated in either SI units or inch-pound units are to be regarded as standard. Within the text, the inch-pound units are shown in brackets. The values stated in each system are not exact equivalents; therefore, each system must be used independently of the other.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation:D4428/D4428M–00
Standard Test Methods for
Crosshole Seismic Testing
This standard is issued under the fixed designation D4428/D4428M; the number immediately following the designation indicates the
year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last
reapproval. A superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope * 2. Significance and Use
1.1 These test methods are limited to the determination of 2.1 The seismic crosshole method provides a designer with
horizontally traveling compression (P) and shear (S) seismic information pertinent to the seismic wave velocities of the
waves at test sites consisting primarily of soil materials (as materials in question (1). This data may be used as input into
opposed to rock). A preferred test method intended for use on static/dynamic analyses, as a means for computing shear
critical projects where the highest quality data must be ob- modulus, Young’s modulus, and Poisson’s ratio, or simply for
tained is included. Also included is an optional method the determination of anomalies that might exist between
intended for use on projects which do not require measure- boreholes.
ments of a high degree of precision. 2.2 Fundamental assumptions inherent in the test methods
1.2 Various applications of the data will be addressed and are as follows:
acceptable interpretation procedures and equipment, such as 2.2.1 Horizontal layering is assumed.
seismic sources, receivers, and recording systems will be 2.2.2 Snell’s laws of refraction will apply. If Snell’s laws of
discussed. Other items addressed include borehole spacing, refraction are not applied, velocities obtained will be unreli-
drilling, casing, grouting, deviation surveys, and actual test able.
conduct. Data reduction and interpretation is limited to the
3. Apparatus
identification of various seismic wave types, apparent velocity
3.1 The basic data acquisition system consists of the fol-
relation to true velocity, example computations, effective
boreholespacing,useofSnell’slawofrefraction,assumptions, lowing:
3.1.1 Energy Sources—These energy sources are chosen
and computer programs.
1.3 It is important to note that more than one acceptable accordingtotheneedsofthesurvey,theprimaryconsideration
being whether P-wave or S-wave velocities are to be deter-
device can be used to generate a high-quality P wave or S
mined. The source should be rich in the type of energy
wave,orboth.Further,severaltypesofcommerciallyavailable
receiversandrecordingsystemscanalsobeusedtoconductan required, that is, to produce good P-wave data, the energy
source must transmit adequate energy to the medium in
acceptable crosshole survey. Consequently, these test methods
primarilyconcerntheactualtestprocedure,datainterpretation, compression or volume change. Impulsive sources, such as
explosives, hammers, or air guns, are all acceptable P-wave
and specifications for equipment which will yield uniform test
results. generators. To produce an identifiable S wave, the source
should transmit energy to the ground primarily by directional-
1.4 The values stated in either SI units or inch-pound units
are to be regarded as standard. Within the text, the inch-pound ized distortion. For good S waves, energy sources must be
repeatable and, although not mandatory, reversible. The
units are shown in brackets. The values stated in each system
are not exact equivalents; therefore, each system must be used S-wave source must be capable of producing an S-wave train
with an amplitude at least twice that of the P-wave train. Fig.
independently of the other.
1.5 This standard does not purport to address all of the 1 and Fig. 2 show examples of impulse and vibratory seismic
sources.
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro- 3.1.2 Receivers—The receivers intended for use in the
crosshole test shall be transducers having appropriate fre-
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use. quency and sensitivity characteristics to determine the seismic
wave train arrival. Typical examples include geophones and
accelerometers.Thefrequencyresponseofthetransducermust
ThesetestmethodsareunderthejurisdictionofASTMCommitteeD18onSoil
not vary more than 5% over a range of frequencies from ⁄2to
and Rock and are the direct responsibility of Subcommittee D18.09 on Dynamic
Properties of Soils.
Current edition approved Jan. 10, 2000. Published March 2000. Originally
published as D 4428/D 4428M – 84. Last previous edition D 4428/ Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof
D4428M–91(1995). this standard.
*A Summary of Changes section appears at the end of this standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D4428/D4428M
seismograph. Permanent records of the seismic events shall be
made by either scope-mounted camera or oscillograph.
4. Procedure
4.1 Borehole Preparation:
4.1.1 Preferred—The preferred method for preparing a
borehole set for crosshole testing incorporates three boreholes
in line, spaced 3.0 m [10 ft] apart, center-to-center on the
groundsurface,asillustratedinFig.3.If,however,itisknown
that S wave velocities will exceed 450 m/s [1500 ft/s], such as
is often encountered in alluvial materials, borehole spacings
may be extended to 4.5 m [15 ft].
4.1.1.1 Drill the boreholes, with minimum sidewall distur-
bance, to a diameter not exceeding 165 mm [6.5 in.].After the
drillingiscompleted,casetheboringwitheither75or100mm
[3 or 4 in.] inside diameter PVC pipe or aluminum casing.
Before inserting the casing, close the bottom of the pipe with
FIG. 1 Reversible Impulse Seismic Source (Produces Both P and
S Wave Trains) a cap which has a one way ball-check valve capable of
accommodating 38 mm [1 ⁄2 in.] outside diameter grout pipe.
Center the casing with spacers and insert it into the bottom of
2 times the predominant frequency of the site-specific S-wave the borehole. Grout the casing in place by (1) inserting a 38
train. Each receiving unit will consist of at least three trans- mm [1 ⁄2 in.] PVC pipe through the center of the casing,
ducers combined orthogonally to form a triaxial array, that is, contacting the one-way valve fixed to the end cap (Fig. 4 (side
one vertical and two horizontal transducers mounted at right
A)), or (2) by a small diameter grout tube inserted to the
angles, one to the other. In this triaxis arrangement, only the bottom of the borehole between the casing and the borehole
vertical component will be acceptable for S-wave arrival
sidewall(Fig.4(sideB)).Anotheracceptablemethodwouldbe
determinations.IncaseswhereP-wavearrivalsarenotdesired, to fill the borehole with grout which would be displaced by
auniaxialverticaltransducermaybeused.P-wavearrivalswill end-capped fluid-filled casing. The grout mixture should be
be determined using the horizontal transducer oriented most formulated to approximate closely the density of the surround-
nearly radially to the source.The transducer(s) shall be housed ing in situ material after solidification. That portion of the
in a single container (cylindrical shape preferred) not exceed- boring that penetrates rock should be grouted with a conven-
ing 450 mm [18 in.] in length. Provision must be made for the tional portland cement which will harden to a density of about
3 3
container to be held in firm contact with the sidewall of the 2.20 Mg/m [140 lb/ft ]. That portion of the boring in contact
borehole.Examplesofacceptablemethodsinclude:airbladder, with soils, sands, or gravels should be grouted with a mixture
wedge, stiff spring, or mechanical expander. simulating the average density of the medium (about 1.80 to
3 3
3.1.3 Recording System—The system shall consist of sepa- 1.90 Mg/m [110 to 120 lb/ft ]) by premixing 450 g [1 lb] of
rate amplifiers, one for each transducer being recorded, having bentonite and 450 g [1 lb] of portland cement to 2.80 kg [6.25
identical phase characteristics and adjustable gain control. lb] of water. Anchor the casing and pump the grout using a
Onlydigitalsignalfilteringwillbeacceptable.Analogfiltering, conventional, circulating pump capable of moving the grout
active or passive, will not be acceptable because of inherent throughthegroutpipetothebottomofthecasingupwardfrom
phase delays. The receiver signals shall be displayed in a the bottom of the borehole (Fig. 4). Using this procedure, the
manner such that precision timing of the P and S-wave arrival annular space between the sidewall of the borehole and the
referenced to the instant of seismic source activation can be
casing will be filled from bottom to top in a uniform fashion
determined within 0.1 ms when materials other than rock are displacingmudanddebriswithminimumsidewalldisturbance.
being tested. Timing accuracy shall be demonstrated both
Keep the casing anchored and allow the grout to set before
immediately prior to and immediately after the conduct of the using the boreholes for crosshole testing. If shrinkage occurs
crosshole test. Demonstrate accuracy by inducing and record- near the mouth of the borehole, additional grout should be
ing on the receiver channels an oscillating signal of 1000 Hz inserted until the annular space is filled flush with the ground
derived from a quartz-controlled oscillator, or, a certified surface (4).
laboratory calibration obtained within the time frame recom- 4.1.2 Optional—If the scope or intended use of a particular
mended by the instrument manufacturer. Further, the timing project does not warrant the time and expense which would be
signal shall be recorded at every sweep rate or recorder speed, incurredbythepreferredmethod,orifthespecificprojectsuch
or both, used during conduct of the crosshole test. As an as an investigation beneath a relatively small machine founda-
optional method, the true zero time shall be determined by (1) tion is undertaken, this optional method may be used.
asimultaneousdisplayofthetriggeringmechanismalongwith 4.1.2.1 In all cases, a minimum of two boreholes must be
atleastonereceiver,or(2)alaboratorycalibration(accurateto used. If the borings are to be 15 m [50 ft] deep or less,
0.1 ms) of the triggering mechanism which will determine the verticality will be controlled using a level on the drill stem
lapsed time between the trigger closure and development of extending into the borehole. Center-to-center surface borehole
thatvoltagerequiredtoinitiatethesweeponanoscilloscopeor spacing will be determined by the nature of the project.
D4428/D4428M
FIG. 2 Borehole Vibratory Seismic Source (Produces S Wave Train Only)
FIG. 3 Crosshole Seismic Test
Boringsmaybeusedeitherwithorwithoutcasing;however,if spacing exceeds 6.0 m [20 ft], the probability of measurement
casing is used, grout must be injected between the casing and of refracted waves rather than a direct wave in each layer
sidewall of the borehole to ensure good contact in the manner greatly increases. As a consequence, data obtained by the
described in 4.1.1.1. If the center-to-center surface borehole optional method must be used with caution.
D4428/D4428M
FIG. 4 Acceptable Grouting Techniques
4.2 Borehole Deviation Survey—A borehole deviation sur- 4.2.2.3 Limit the maximum depth of investigation to less
vey must be conducted to determine accurately the horizontal than 15 m [50 ft]. If the depth of investigation exceeds 15 m
[50 ft] a deviation survey such as described in 4.2.1 must be
distance between borings.
conducted.
4.2.1 Preferred Method— Conduct a borehole deviation
4.2.2.4 If casing is used, grout as described in 4.1.1, then
survey in all three crosshole borings with an instrument
evacuate all fluid from the interior and insert a lighted
capable of measuring the precise vertical alignment of each
plumb-bob observing its attitude at 3-m [10-ft] intervals. If the
hole. The instrument must have the capability of determining
plumb-bob strikes the sidewall, note that depth and the
horizontal orientation with a 2° sensitivity and an inclination
direction of deviation.
range from 0 to 30° with a sensitivity of 0.1°. Information thus
4.2.2.5 Estimate the distance between borings and provide
obtained will enable the investigator to compute true vertical
appropriate caution statements on all data.
depth and horizontal position at any point within the borehole
4.3 Crosshole Test:
so that actual distance between the holes can be computed to
4.3.1 Preferred Method— Begin the crosshole test by plac-
within 62% to a depth of about 30.0 m [100 ft].
ing the energy source in an end hole at a depth no greater than
4.2.1.1 Proceed with the survey beginning at the mouth of
1.5 m [5 ft] (Fig. 3) into the stratum being investigated. Place
theboreholeobtainingdeviationdataatintervalsnotexceeding
the two receivers at the same elevation in each of the
3.0 m [10 ft] to the bottom of the boring. Repeat the
designated receiver holes. Clamp the source and receivers
measurementsonthewithdrawaltripatintervalsnotexceeding
firmly into place. Check recording equipment and verify
6.0 m [20 ft] so that closure can be determined at the mouth of
timing. Activate the energy source and display both receivers
the borehole.
simultaneously on the recording device. Adjust the signal
4.2.2 Optional Method— If the scope of a project dictates
amplitude and duration such that the P-wave train or S-wave
the use of the optional procedure described in 4.1.2, the
train, or both, are displayed in their entirety.
following precautions must be undertaken to ensure verticality
4.3.1.1 Best results will be obtained by performing two
of the borings.
separate tests: one optimized for P-wave recovery (fastest
4.2.2.1 Level the borehole drilling apparatus using a level
sweep/recorder rate, higher gain settings) and the second for
placed on the drill stem extending into the mouth of the
S-wave recovery (slower sweep/recorder rate, lower gain
borehole.
settings). If enhancement equipment is being used, repeatedly
4.2.2.2 As drilling progresses, recheck the drill stem at 3.0
activate the energy source until optimum results are displayed.
m [10 ft] depth intervals and realign as necessary. Do not overrange memory circuitry. A clipped signal is
D4428/D4428M
unacceptable. Perform the second test by lowering the energy The apparent velocity is equal to 1 divided by the travel
source and receivers to a depth dictated by kn
...
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