Geophysical Exploration for Cavity Detection in Karst Terrain

Detection of poor quality rock and voids has been a major research activity of the U. S. Army Engineer Waterways Experiment Station (WES) since the mid 1970's. The principal objective of this work was to refine and/or develop geophysical methodology and analysis procedures for detecting and delineating cavities and discontinuities in rocks. A major part of this effort was to evaluate the effectiveness of a variety of promising geophysical methods in karstic terrain. To this end, electrical resistivity, surface seismic, crosshole seismic, acoustic resonance, electromagnetic (radar) and microgravity methods were tested at karst sites having well documented features of interest. Selected examples of the site investigations are presented and results are discussed. Guidelines are offered for the most promising methods to use in reconnaissance and high-resolution surveys to detect/delineate cavities in karstic areas.