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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Data reduction and interpretation is limited to the identification of various seismic wave types, apparent velocity relation to true velocity, example computations, effective borehole d44228, use of Snell’s law of refraction, assumptions, and computer programs. In order to have quantitative and 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.
During phase two field exploration, the information gathered is more critical to the analytical site-specific Characterization.
Users of these test methods are cautioned f4428 compliance with Practice D does not in itself assure reliable results. Figure 5 shows a portion of the waveforms collected over the depth interval Bureau of Reclamation, In crosshole testing, the seismic measurements encroach closer to the water surface with each successive depth interval.
Low-strain material damping and inelastic attenuation values can also be obtained from crosshole surveys. Active view current version of standard. The effect of increasing velocity with depth is greatest within thick homogeneous soil deposits. 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 xstm refraction, assumptions, and computer programs.
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. Inch-pound units are provided for convenience. Another critical element of crosshole testing, which is often ignored, is the requirement for borehole directional surveys. Compute total direct travel time: Typically, either forward or inverse modeling for cross-borehole seismic investigations consists of computing synthetic travel times to test the ray path coverage and resolution of either unknown or identified velocity anomalies, respectively.
Increasing velocity with depth implies the seismic ray path is nearly circular between source and receiver, asfm sensing deeper higher velocity material as the source-receiver separation increases. 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.
Further, several types of commercially available receivers and recording systems can also be used to conduct an acceptable crosshole survey. Using source-receiver systems with preferential orientations in tandem i.
Standard Test Methods for Crosshole Seismic Testing
There are studies, however, which indicate significant velocity dependence of the SV- and SH-waves due to anisotropic states of stress in either the horizontal or vertical stress field particularly in soil aatm Redpath, et al.
Based on 10 years of experience, since the inception of the ASTM standard incrosshole geophysical surveys have become more widely used and accepted for engineering as well as environmental applications.
The values stated in each system may not be exact equivalents; therefore, each system shall c4428 used independently of the other. 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. 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.
Because of this, the crosshole test permits much easier interpretation of direct arrivals in the recorded waveforms. Link to Active This link will always route to the current Active version of the standard. In this case, the two horizontal axis geophones must remain oriented, radially and transversely, throughout the survey.
Several techniques to plug the porosity of the surrounding formation are commercially available e. Utilizing digital recording equipment affords the operator the ability to store the data on magnetic media for analysis at a later date; but more importantly, digital data can be filtered, smoothed, and time-shifted during analysis.
This permits timing direct arrivals directly off the waveform. Historical Version s – view previous versions of standard. When approaching d428 interfaces, refracted-wave arrivals begin to be timed as the first arrival, which could easily be misinterpreted as direct-wave arrival. Within the text, the inch-pound units are shown in brackets. 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.
Apparent V 1 refracted velocity. There are a number of digital signal processing techniques useful for determining material properties other than P- or S-wave velocity, as well as confirming the computed crosshole velocity profile, such as: Stokoe demonstrated that particle motions generated with different seismic source types 4d428 during crosshole testing are three-directional.
Standard – Standard Test Methods for Crosshole Seismic Testing ASTM D/DM –
Also, because each drill hole was cased for the crosshole tests, additional geophysical surveys should be conducted. Crosshole velocity data are valuable for assessing man-made materials, soil deposits, or rock formations. Because boreholes are required, there is the opportunity to obtain more site-specific geotechnical information, which, when integrated with the seismic data, yields the best assessment for the engineering application liquefaction, deformation, or strong motion Characterization.
Reporting of test results in units other than D44228 shall not be regarded as nonconformance with this test method. Theoretically, there is no difference in the body wave velocity for SV- and SH-waves, which justifies use of the uncomplicated vertical source for generation of SV-waves, and vertically oriented geophones for signal detection. If an SH-wave source is selected, then horizontal geophones must be used and oriented as previously described to detect the SH-wave arrivals.
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.
Crosshole measurements rely considerably on the premise that the trigger time is precisely known as well as recorded. Also, lithologic information such as stratigraphy and material type are determined from the drilling and sampling program prior to seismic data acquisition; this allows astmm constraints, or boundary conditions, to be placed on the field data along the boundaries of the material between the boreholes.
In this system, the pound lbf represents a unit of force weightwhile the unit for mass is slugs. Link to Active This link will always route to the current Active version of the standard. Comparing both sets of direct wave velocities, that is, source to receiver No. For engineering applications, there is not much advantage in sstm via modeling the ray coverage or residual velocity resolution because crosshole testing at the engineering asm utilizes a simple horizontal, straight-ray path geometry to determine average velocity.