A New Interpretation Technique Of Surface Wave Measurements For Geotechnical Profiling

Non-invasive shear wave velocity (SWV) profiling of soil deposits has long been<br>recognized as a cost-effective approach to obtain SWV data essential for seismic response<br>analysis including site amplification and liquefaction. The controlled-source<br>measurement of surface wave dispersion (CXW) is a relatively new non-invasive method<br>that is used for site characterization in the USA, Japan, and other countries. The CXW<br>method uses harmonic controlled sources to produce steady state Rayleigh waves in order<br>to measure the dispersion characteristics of soil and rock. Several interpretation<br>techniques may be used to obtain SWV structure from Rayleigh waves dispersion data<br>(in a process that is referred to as the Vf-Vs method). CXW measurement data from<br>more than 200 soil and rock sites were analyzed. These results were used to formulate<br>a new approach for the Vf-Vs interpretation method based on the new concept of<br>reference profiles that describes the average dispersion curve and SWV structure. The<br>reference profile is based on SWV dependency on confining pressure (depth) in soils.<br>Simple equations were developed for direct inversion of the reference profile. The new<br>procedure is completed by considering the effects of single layers with properties that are<br>different than the reference profile. This new interpretation procedure is rapid and<br>computationally efficient and its results are more representative of actual soil structure<br>than results obtained from other non-invasive methods. This paper shows that inversion<br>based on surface waves dispersion can provide a good estimate of average SWV<br>variation.