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| | Abstract | | S-wave velocity is one of the most important physical properties of the near surfaces for assessing seismic resistance, characterizing stiffness of the ground for geotechnical engineering practices. Whereas engineering geophysicists have been trying to provide more precise and reliable information on Vs structure from PS logging data, geotechnical engineers blamed that S-wave velocity data did not match with such conventional geotechnical testing data as SPT N-values and have still regarded the PS logging with suspicion. The author collected a number of PS logging data and laboratory test data of the surface unconsolidated sediments and analyzed them statistically. The conclusions are as follows: First, inconsistency between the data was basically attributed to the difference in measurement scale. Most of the laboratory tests are applied to small specimen at most 10 cm long, 5 cm diameter. In contrast, suspension PS logging provides us average values for 1 m long columns. Second, nevertheless their averaged properties, precisely measured S-wave velocities showed good relationship with physical properties such as solidity, water content, and mean diameter. In addition, it is possible to estimate N-values from S-wave velocity data, but the opposite is very hard due to nonlinearity of N-values. A high-resolution, short-spacing multichannel S-wave logging tool are needful to emulate laboratory testing, SPT and to investigate geophysical properties of the surface sediments. |
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