Civil Engineering Association

Geophysical Methods Commonly Employed for Geotechnical Site Characterization

This circular offers an overview of 12 geotechnical geophysical methods that are commonly applied to transportation projects. Geotechnical geophysics is the application of geophysics to geotechnical engineering problems; such investigations normally extend to total depths of less than 300 ft. Geotechnical geophysical surveys are performed on the ground surface, within boreholes and water, and from the air. Using illustrations and brief examples, commonly employed geotechnical geophysical methods are described. Through summary tables and brief discussions, common applications of engineering geophysics are presented. Chapters are devoted to the selection of appropriate geophysical methods and geophysical contractors, respectively. Use of geophysics by transportation agencies is reviewed through a summary of NCHRP Synthesis 357: "Use of Geophysics for Transportation Projects" (Sirles, 2006). A detailed description of applications of geophysical methods to highway-related problems may be found at www.cflhd.gov/agm/index.htm.