Characterization of Weathered Limestone Using Cross-Hole Ground Penetrating Radar Techniques

In-situ geotechnical characterization of weathered limestone in Florida is important because typical drilling operations may not provide sufficient core specimens for testing. Cross-hole ground penetrating radar was used to characterize a sequence of soil overlying weathered limestone bedrock at a geotechnical test site in north central Florida. Zero offset profiling (ZOP) provided radar velocity as a function of depth between boreholes. Multiple offset gather (MOG) data was used to produce a radar velocity tomogram between boreholes. Using published radar velocities as a guide, it was possible to distinguish the stratigraphy in the boreholes. The radar velocity based stratigraphy compared well to information from driller’s logs which were produced during the installation of the cased borings. Using the MOG tomograms, a cavity within the bedrock could clearly be identified. The radar velocities noted within the limestone were less than published results which is due to the highly weathered nature of the limestone at the site. Cross-hole ground penetrating radar can be a valuable tool for geotechnical site characterization.