Seismic Tomography for the Integrity Assessment of Earthen Dams and Levees.

Dams are a vital part of a nation\u27s infrastructure. Considering the fact that many of the dams in the United States have approached or are approaching their projected life expectancy of 50 years, these critical infrastructures represent a risk to public safety. Minimizing this risk requires an ongoing safety inspection, monitoring, maintenance and rehabilitation program. This research examines the use of a non-invasive geophysical seismic method to provide additional information where the usual visual inspection is insufficient and the comboring investigation is not an option. Even though seismic techniques provide valuable information of the subsurface strata, the interpretation is not always uniform and consistent. In this research, three seismic survey techniques, known as seismic refraction, Multichannel Analysis of Surface Waves (MASW) and shear wave surveys were jointly considered for the purpose of dam integrity assessment. Multiple techniques were applied to an earthen embankment dam with no known defects near Oxford, Mississippi, and seismic refraction surveys were conducted on another earthen dam in Lawrence County, Alabama, which has known problems associated with seepage. Seismic tomograms are built using commercially available software for the interpretation of data collected. The results provided insights on the natural seismic variability of earthen dams. Some inferences are made on how seismic tomography images can be used to detect compromised zones (i.e. seepage, piping, etc) within earthen embankment dams