Seismic cone analysis using digital signal processing for dynamic site characterization

Abstract

In situ measurement of the dynamic characteristics of surficial soils is becoming more common in geotechnical practice for prediction of ground-surface motions from earthquake excitation and to evaluate foundations for vibrating equipment. Techniques for these measurements have been under development at the University of British Columbia (UBC) since 1980. The paper discusses many practical considerations with respect to equipment (sources, receivers, trigger, etc.) and procedures that can affect the interpretation and analysis of seismic cone results. A brief review is given of the cross-over method as used at UBC to determine interval shear velocity travel times from downhole seismic cone testing. A more detailed description is provided for the cross-correlation technique used in the frequency domain, which has recently been incorporated into the analysis procedure. Comparisons of these two methods are presented and discussed. It has been found useful to isolate the main shear wave before further calculations, and the effects of this procedure are provided. A summary of findings concerning the characteristics of the measured signals is also included. Key words : seismic, cone penetrometer, sources, receivers, accelerometers, shear wave, velocity, downhole, digital, signal processing.