Near-surface geophysical techniques have been widely used in a great variety of applications for characterizing underground features. However, selecting appropriate geophysical survey techniques can be critical in producing desired imaging resolutions, especially in situations where underground features are complicated. In this application, underground geophysical imaging was aimed to detect small-scale soil voids at several levee locations at San Joaquin County, California, where water aqueducts of metal pipelines cross through. Electrical resistivity tomography in combination with induced polarization techniques were employed to obtain subsurface imaging to detect potential soil voids and to determine the extent of voids distribution. Data acquisition and data processing were optimized for better resolution. Based on the visual examinations of the levee crossing s, the locations of detected voids which extend to the ground surfaces, seemed accurate. The accuracy of other detected voids which are isolated, discrete voids embedded within the levee crossings will be further verified through other methods. Additional data processing using watershed algorithm by simulated immersion method of boundary detection was performed to quantify the geometries of the resistivity images generated at one of the levee crossings.
AAPG Datapages/Search and Discovery Article #90260 © 2016 AAPG/SEG International Conference & Exhibition, Cancun, Mexico, September 6-9, 2016