Ground Penetrating Radar in the Detection of Subsurface Cavities Related to Sinkhole Activity in Florida

The Florida peninsula is underlain by limestone undergoing continuous solution process resulting in subsurface cavity formation. Increased land development has led to costly structural damage and water supply contamination due to surface subsidence and collapse in areas overlying such cavities. Conventional drilling methods cannot guarantee detection of isolated cavities. A geophysical technique known as ground penetrating radar (GPR) is a non-destructive method in geotechnical investigation capable of surveying large areas quickly and efficiently. GPR works as an echo sounder with a continuous similar graphic display. Cavities are identified by hyperbolic patterns caused by reflections from variations in electrical properties of anomalies as compared to the surrounding material. Due to irregular variations and inconsistencies in the properties of the naturally deposited soils and rocks, interpretation of the result from a radar survey is difficult to pre-determine without an actual field investigation. The intent of this study is to determine those circumstances under which GPR can be of use in the subsurface cavity detection investigations. The results indicate that subsurface conditions in north and central Florida are generally favorable and that this method can be extremely useful in determining trends in subsurface erosion