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Surface Wave Method: A Tool for Lifeline Earthquake Engienering.


pdf icon Surface Wave Method: A Tool for Lifeline Earthquake Engienering. (679 K)
Andrus, R. D.

Earthquake Engineering Site Characterization. Research Needs Workshop Proceedings. Miscellaneous Paper GK-97-21. Appendix G. U.S. Army Corps of Engineers. Final Report. September 1997, U.S. Army Corps of Engineers, Vicksburg, MS, Koester, J. P.; Holmes, T. L., Editor(s)(s), G1-G14 pp, 1997.

Keywords:

earthquakes; geophysical methods; in situ measurement; lifelines; SASW testing; soil liquefaction; shear wave velocity

Abstract:

Liquefaction of granular soils is one of the major causes of lifeline damage in past earthquakes. Screening techniques based on geology, hydrology, and soil conditions can identify areas along the lifeline corridor requiring more rigorous analyses. These areas can extend for several kilometers, however. The Spectral-Analysis-of-Surface-Waves (SASW) method has great potential for rapid determination of the layer thickness and small-strain shear wave velocity, Vs, of soil deposits. The SASW method is nonintrusive and nondestructive. It is based on the principal that surface seismic waves of high frequency propagate only in near-surface layers, and surface waves of low frequency propagate at different velocities if stiffness varies with depth. Thus, different portions of the soil profile can be tested by using surface waves over a wide range of frequencies. The general SASW test configuration of source, receivers, and recording equipment is shown in Figure 1. Liquefaction potential and Vs, of granular soils are influenced by many of the same factors (e.g., density, confinement, and geologic age). This paper evaluates the ability of the SASW method to delineate liquefiable soil using data from two sites (Goddard Ranch and Larter Ranch) where liquefaction occurred during the 1983 Borah Peak, Idaho, earthquake and the liquefaction assessment procedure by Stokoe et al. Application of the SASW method to lifelines is discussed.