Why should you consider this method over crosshole, downhole, or other methods for measuring in-situ shear-wave velocities?
Suspension logging has been used now in both Japan and the United States on many critical structures for more than 20 yrs. It is not new, and is well proven and well documented. Historic projects include the seismic retrofit of all of California’s toll bridges, Yucca Mountain project, and others.
- Suspension Logging offers the only method that gives both P- and Sh-wave velocity measurements reliably in a single hole at depths greater than 200 ft. Other methods which rely on surface sources are limited in depth and resolution.
- Suspension Logging offers high resolution, as little as 20 cm, for resolving thin layers which could have a dramatic effect on surface response. Usually crosshole or downhole data are acquired at 152cm (5ft) intervals.
- Suspension logging can accomplish this in only one hole, whereas Crosshole methods require at least two boreholes.
- Suspension logging is not affected by path effects, which can cause problems for crosshole measurements near a soil-rock interface, or in steeply dipping beds.
- Suspension logging is optimized for soil and soft rock, and provides much better penetration than full-waveform sonic tools, yielding more accurate results, particularly for P-wave measurements.
- Suspension logging can be used reliably in either cased, or uncased boreholes.
- Suspension logging can be easily used in marine applications, off barges or Jack-up platforms
- Suspension logging provides two independent measurements of shear-wave velocity, providing an internal QA check. These include both a Receiver-to-Receiver measurement (both forward and reverse) as well as a Source-to-Receiver measurement.