Surface Wave Testing for In Situ Characterization of Geologic Materials: Geotechnical Applications, Limitations, and Recent Advances

JOSEPH THOMAS COE, JR., PH.D.
Assistant Professor, Temple University
 

ABSTRACT: Current standards of practice for subsurface investigation can leave geotechnical engineers with an incomplete understanding of site conditions, particularly when anomalous subsurface features exist at a site.

To address this issue, geotechnical engineers have increasingly used geophysical methods to measure the shear wave velocity (VS) as a proxy for stiffness of near surface strata. Surface wave methods such as the Spectral Analysis of Surface Waves (SASW) and Multichannel Analysis of Surface Waves (MASW) in particular have been developed within the last few decades as the demand for rapid and accurate VS profiles has increased. Surface waves are often the strongest signals obtained from seismic geophysical testing. Their high signal to noise ratio make surface wave methods quite robust during the data acquisition stage. Surface waves methods extract the site-specific velocity-frequency dependency and utilize an inversion procedure to estimate a subsurface VS profile. However, care should be exercised with interpretation as there is an appreciable amount of uncertainty inherent in the measurements and introduced during data postprocessing. This presentation initially provides a discussion regarding the theoretical aspects of surface wave testing as well as the fundamentals of data acquisition and post-processing. A series of application-based case histories are presented to demonstrate the strengths and limitations of MASW in particular. Finally, a discussion is provided of recent advances to improve MASW.

BIOGRAPHY: Dr. Joseph Coe is an Assistant Professor at Temple University. Prior to joining Temple University, he was an Assistant Professor at The Citadel in Charleston, South Carolina. He obtained his Civil Engineering Ph.D., M.S., and B.S. (Geology minor) degrees from the University of California Los Angeles (UCLA). His career in geotechnical engineering spans twelve years primarily as a researcher with nondestructive and geophysical imaging systems, instrumentation and sensor technology, field experimentation and data acquisition, and laboratory scale models. His research interests predominantly relate to geophysical site characterization, nondestructive evaluation and rehabilitation of foundations, bridge scour, and urban
seismic hazards, particularly as related to resiliency of infrastructure systems.