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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S-waves generated in crosshole testing may be split into two wave types, each with different particle motions–SV- and SH-waves, vertical or horizontal particle motions, respectively. Since seismic wave travel times should be measured to the nearest tenth of a millisecond, relative borehole positions should be known to within a tenth of a foot.
Therefore, the following sequence of eight steps equations will confirm detection of refracted-wave travel time or direct-wave travel time at each recording depth ASTM Reliable results depend on many factors; Practice D provides a means of d448 some of those factors. Basically, borehole preparation and completion procedures are the success or failure of crosshole seismic testing.
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Based on this discussion, to ensure that true in 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.
During phase two field exploration, the information gathered is more critical to the analytical site-specific Characterization.
Typically, crosshole surveys are a geophysical tool for performing explorations during what are considered phase two field investigations where phase one field investigations include surface geophysical surveys, follow-up drilling, trenching, and sampling of the in situ materials. 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 v4428 electricaland permits both empirical and theoretical correlation with other geotechnical material parameters.
As the vadose zone and water surface are encountered, P-wave velocities become dependent upon the percent saturation, and the Poisson’s ratio is no longer a valid representation of the formation characteristics. Referenced Documents purchase separately The documents listed below are referenced within the subject standard but are not provided as part of the standard. Bureau of Reclamation has encountered numerous sites in the western United States where loose, liquefiable d428 and gravel deposits needed to be investigated, and crosshole testing effectively evaluated the in situ material density and stiffness with P- and S-wave velocities, respectively; however, astmm care and caution were used for completion of each borehole U.
Reporting of test results in units other than SI shall not d44228 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.
When approaching seismic interfaces, refracted-wave arrivals begin to be timed as the first arrival, which could easily be asstm as direct-wave arrival.
ASTM D / DM – 07 Standard Test Methods for Crosshole Seismic Testing
For engineering applications, digital signal processing in crosshole seismic tests is, similar to modeling, of minimal value. Some deposits have linearly increasing velocity with depth, primarily due to vertical pressures, where the apparent velocity for each depth can be computed with.
With three-component geophones, there is one vertically oriented geophone and two horizontal geophones. However, the most robust application of crosshole testing is the ability to define in situ shear-wave velocity profiles for engineering investigations associated with earthquake engineering Mooney, In this system, the pound lbf represents a unit of force weightwhile the unit for mass is slugs.
Compare T rfr with T dir and T meas. Data Acquisition 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. This standard does not purport to address all of the safety concerns, if any, associated with its use.
In this case, the two horizontal axis geophones must remain oriented, radially and transversely, throughout the survey. 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.
Figure 1 illustrates a general field setup for the crosshole seismic test method. Crosshole SV-wave paired borehole records at five depths.
In this example, refractions occur in a situation similar to that depicted in figure 3; that is, refractions d4428 from high-velocity materials either above or below the low-velocity layer. Also, digital signal processing may be directly performed for coherence, frequency-dependent attenuation, and spectral analysis. Also, depending upon the velocity contrast across layer boundaries, direct arrivals through low-velocity layers are generally larger amplitude and thereby recognizable.
The clamping device should not affect the mechanical response of the geophone i. This becomes uniquely critical when only two drill holes are asfm i.
When layers of alternating density or stiffness are either known to exist or are encountered during phase one field investigations, crosshole seismic tests are recommended to define the in situ velocities within each layer. sstm
Standard Test Methods for Crosshole Seismic Testing
Consequently, these test methods primarily concern the actual test procedure, data interpretation, and specifications for equipment which will yield uniform test results. For interpretation of direct ray path travel times between two or three boreholes, the Bureau of Reclamation Sirles, Custer, and McKisson, has published a computer program that is designed specifically for reducing crosshole seismic data.
Sites where noninvasive techniques are required due to hazardous subsurface conditions, crosshole seismic tests are not applicable because of tight regulatory procedures regarding drilling, sampling, and decontamination. In these cases, V app is a function of depth zV i is the initial velocity at zero depth, and K is the increase in velocity ast unit depth.
General Crosshole Procedures | Environmental Geophysics | US EPA
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. In addition, they are representative of the significant digits that should generally be retained. 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.
The logic and flowt for this interpretation and data presentation program are designed to follow the typical field data acquisition process i. Therefore, a systematic comparison of measured travel times, computed direct velocities, and interval velocities at each recording depth enables interpretation of true in situ velocity at all measurement depths.
Comparing both sets of direct wave velocities, that is, source to receiver No. 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. Other items addressed include borehole spacing, drilling, casing, grouting, deviation surveys, and actual test procedures.
The requirement for multiple drill holes in crosshole testing means that care must be taken when completing each borehole with casing and grout. Users of these test methods are cautioned that compliance with Practice D does not in itself assure reliable results.
Crosshole geophysical testing is generally conducted in the near surface upper hundred meters for site-specific engineering applications Sirles and Viksne, All of the dynamic elastic moduli of a material can be determined from knowledge of the in situ density, P- and S-wave velocity.