ASTM D4428 PDF
These test methods are limited to the determination of the velocity of two types of horizontally travelling seismic waves in soil materials. GEOPHYSICAL SYSTEMS. NDE ™» One Platform – Multiple NDE Tests geo- Crosshole/Downhole Seismic» ASTM D/DM/D(DS). Crosshole seismic test procedures are outlined in ASTM test designation D M (). The ASTM procedures provide specific.
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Crosshole techniques are most useful when phase one site explorations indicate horizontal and particularly vertical variability of material properties. Also, lithologic information such as stratigraphy and material type are determined from the drilling and sstm program prior to seismic data acquisition; this allows reliable constraints, or boundary conditions, to be placed on the field data along the boundaries of the material between the boreholes.
ASTM D / DM – 14 Standard Test Methods for Crosshole Seismic Testing
For interpretation of direct ray path travel times between two or three boreholes, s4428 Bureau of Reclamation Sirles, Custer, and McKisson, has published a computer program that is designed specifically for reducing crosshole seismic data. The objective of acquiring crosshole data can be multipurpose; that is, the seismic velocity results obtained may be used for evaluation of lateral and vertical material continuity, liquefaction analyses, deformation studies, or investigations concerning amplification or attenuation of strong ground motion.
Other items addressed include borehole spacing, drilling, casing, grouting, deviation surveys, and actual test conduct. 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 asgm. Compute hypotenuse distance H i: In this example, refractions occur in a situation similar to that depicted in figure 3; that is, refractions occur from high-velocity materials either above or below the low-velocity layer.
Xstm Documents purchase separately The documents listed below are referenced within the subject standard but are not provided as part of the standard. Using source-receiver systems with preferential orientations in tandem i. This sample problem, or example data set, illustrates three distinct advantages that crosshole testing has over conventional surface geophysical axtm for these types of investigations: Compare T rfr with T dir and T meas. In this system, the pound lbf represents a unit of force weightwhile the unit for mass is slugs.
Numerous studies have shown that the effects on crosshole measurements by the choice of geophone are not critical to the results e. Also, depending upon the velocity contrast across layer boundaries, direct arrivals asstm low-velocity layers are generally larger amplitude and thereby recognizable. Hoar’s dissertation shows that with proper borehole completion, digital recording equipment, and a preferential source-receiver system, asgm reversed polarized and interpretable S-wave signals are relatively easy to acquire.
General Crosshole Procedures Introduction The primary purpose of obtaining crosshole data is to obtain the most detailed in situ seismic wave velocity profile for site-specific investigations and material Characterization. Although both phase one and phase two results are important, the two independent sets of data must be integrated into the final analysis.
Standard Test Methods for Crosshole Seismic Testing
The procedures used do not consider material variation, purpose for obtaining the data, special purpose studies, or any considerations for the users objectives; and it is common practice to increase or reduce significant digits of reported data to be commensurate with these considerations.
The primary detriments or obstacles encountered during crosshole testing are typically related to the placement and completion of multiple drill holes. Typically, the S-wave generated in most crosshole testing is the SV-wave, which is a vertically polarized horizontally propagating shear wave.
Other items addressed include borehole spacing, drilling, casing, grouting, deviation surveys, and actual test conduct.
Crosshole SV-waves showing direct D and refracted R arrivals. The objective of this investigation was to determine if a low-velocity alluvial layer exists beneath the embankment, which was constructed in These SV-waves are easiest to generate because of commercially available borehole impact hammers that have reversible impact directions up or downand they are also the easiest to record because only one vertically oriented geophone is required in each receiver borehole.
Comparing both sets of direct wave velocities, that is, source to receiver No. P-waves are generated with a sparker or small explosive device one that will not damage the PVC casing such that along the assumed straight-ray propagation path the seismic impulse compresses and rarefies the materials radially toward the receiver borehole s.
Figure 1 illustrates a general field setup for the crosshole seismic test method.
Historical Version s – view previous versions of standard. Reporting of test results in units other than SI shall not be regarded as nonconformance with this test method. Also included is an optional method intended for use on projects which do not require measurements of a high degree of precision. The pages found under Surface Methods and Borehole Methods are substantially ba sed on a report produced by the United States Department of Transportation: Based on this discussion, to ensure that true adtm situ velocities are presented, crosshole measurements should be performed a minimum of four measurement intervals below the zone of concern to adequately define the velocity profile.
D428 total direct travel time: Inch-pound units are provided for convenience.
Standard – Standard Test Methods for Crosshole Seismic Testing ASTM D/DM –
The comparative technique for defining the refractor velocities outlined above assumes that the velocities are constant within each layer; however, occasionally this is an oversimplification.
Due to the different particle motions along the seismic ray path, it is crucial to use optimal source-receiver systems in order asym best record crosshole P- or S-waves Hoar, Experience has proven that for optimal measurement of the P-wave signal, a hydrophone has the greatest pressure-pulse sensitivity for compressional-wave energy.
Direct-wave arrivals are easily recognized even with low-amplitude refracted arrivals as long as the previously described field equipment is utilized for preferential d4482 of P-waves or polarized SV or SH-waves. This technique of reducing data d4248 the field has proven its value because of the ability to determine optimal testing intervals and adjust the program as necessary to address the site-specific problem.
Crosshole measurements rely considerably on the premise that the trigger time is precisely known as well as recorded. It is scientifically undesirable to combine the use of two separate sets of inch-pound units within a single standard.
For example, in crosshole testing, the first f4428 is not always the time of arrival of the direct ray path.