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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Recording instruments used in crosshole testing vary considerably, but there are no standard requirements other than exact synchronization of the source pulse and instrument trigger for each recording. Historical Version s – view previous versions of standard.
Combining values from the two systems may result in nonconformance with these test methods. Also, lithologic information such as d44428 and material type are determined from the drilling and sampling 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.
In order to have quantitative astk quality assured results, crosshole tests performed for either engineering or environmental problems should be conducted in accordance with procedures established by the American Society for Testing and Materials ASTM. Xstm, of course, assumes field data are acquired properly and no analog filtering or digital aliasing was performed prior to recording seismic data from each depth.
This is accomplished with loading poles or with geophones that can be electronically oriented. In this example, refractions occur in a situation similar to x4428 depicted in figure 3; that is, refractions occur from high-velocity materials either above or below the low-velocity layer. As stated, these test methods include the gravitational system of inch-pound units and do not use or present the slug ast, for mass.
Referenced Documents purchase separately The documents listed below are referenced within the subject standard but are not provided as part of the standard. Alternatively, SH-waves can be generated and recorded in crosshole testing.
Even small grout takes begin to affect the velocity measured between two closely spaced drill holes.
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. This technique of reducing data in the field has proven its value because of the ability to determine optimal testing intervals and adjust the program as asm to xstm the site-specific problem.
Bureau of Reclamation, Crosshole measurements rely considerably on the premise that the trigger time is precisely known as well as recorded. Using source-receiver systems with preferential orientations in tandem i. Consequently, these test methods primarily concern the actual test procedure, data interpretation, and specifications for equipment which will yield uniform test results.
General Crosshole Procedures | Environmental Geophysics | US EPA
The effect of increasing velocity with depth is greatest within thick homogeneous soil deposits. Matching the formation density with a grout mix is not too difficult, but in open coarse-grained soils, problems arise during grout completion with losses into the formation. Another critical element of crosshole testing, which is often ignored, is the requirement for borehole directional surveys. Asm detailed site information obtained from the crosshole tests with the overall acceptance of the validity of the velocity data, these standards use both empirical correlations for liquefaction and specific input parameters for deformation or ground motion analyses U.
With the deviation logs, corrected crosshole distances between each borehole may be computed and used in the velocity analysis. This standard s4428 not purport to address all of the safety concerns, if any, associated with its use. When approaching seismic interfaces, refracted-wave arrivals begin to be timed as the first arrival, d428 could easily be misinterpreted as direct-wave arrival.
The d4428 trigger signal from zero-time geophones or accelerometers mounted on the downhole impact hammer allows accurate timing for the first arrival at each drill hole.
To illustrate the effect of a high Adtm velocity layer overlying a low S-wave velocity layer on crosshole waveforms, the following sample problem is presented using data acquired at a site in central Utah. Figure 2 shows a series of crosshole SV-waves with reversed polarity note the low amplitude of the P-wave energy compared to the S-wave energy received at both receiver boreholes.
ASTM D / DM – 14 Standard Test Methods for Crosshole Seismic Testing
Inch-pound units are provided for convenience. 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. Dd4428 is paramount that the polarity of each geophone be known prior to data acquisition because the direct arrivals of S-waves with reversed polarity can be easily misinterpreted.
SH-waves also propagate horizontally, but their shear particle motion is in the horizontal plane i. d44428
Standard Test Methods for Crosshole Seismic Testing
V 2 across the seismic interface determine if the refracted wave will arrive before the direct wave. Experience has proven that for optimal measurement of the P-wave signal, a hydrophone has the greatest atsm sensitivity for compressional-wave energy.
Crosshole techniques are most useful when phase one site explorations indicate horizontal and particularly vertical variability of material properties. Data Acquisition Recording instruments used in crosshole astmm vary considerably, but there are no standard requirements other than exact synchronization of the source pulse and instrument trigger for each recording.
Jump to main content. Note 1 — The quality of the results produced by these test methods is dependent on the competence of the personnel asrm it and the d44428 of the equipment and facilities. Acquiring crosshole seismic data resolves hidden layer velocity anomalies that cannot be detected with conventional surface methods, allows both final interpretation of other surface geophysical data seismic or electricaland permits both empirical and theoretical correlation with other geotechnical material parameters.
Compare T rfr with T dir and T meas.
Crosshole geophysical testing is generally conducted in the near surface upper hundred meters for site-specific engineering applications Sirles and Viksne, Some deposits have linearly increasing velocity with depth, primarily due to vertical pressures, where the apparent velocity for each depth can ast computed with. During phase two field exploration, the information gathered is more critical to the analytical site-specific Characterization.
Stokoe demonstrated that particle motions generated with different seismic source types used during crosshole testing are three-directional. Figure 4 shows an example of SV- direct-wave arrivals and refracted-wave arrivals where the arrival time of the direct wave slower can be picked later in the waveform behind the low-amplitude refracted-wave arrival. For successful engineering analysis of coarse-grained materials, crosshole testing is one of the most acceptable geophysical techniques available.
Reliable results depend on many factors; Practice D provides a means of evaluating some of those factors. Comparing both sets of direct wave velocities, that is, source to receiver No. Recently, sites of particular concern for obtaining P- and S-wave velocities are liquefaction studies where the subsurface contains considerable unconsolidated coarse-grained material, and standard geotechnical test procedures blow counts and material sampling cannot effectively evaluate in situ properties.