Comparison of Subsurface Cavity Investigations Using Earth Resistivity, Seismograph and Ground Penetrating Radar

Sinkhole formation in the Central Florida area has become a serious problem. The subsurface exploration method for cavity detection is indeed needed prior to sinkhole development. this research study compares the effectiveness of earth resistivity, seismograph and ground penetrating radar (GPR) methods in the detection of subsurface cavities. A resistivity instrument measures a material\u27s resistance to electric currents. The seismograph measure the propagation velocity of a medium refracting compressional waves. The GPR transmits and receives electromagnetic pulses reflecting off subsurface interfaces. Tests were conducted at two sites: a model test site at the University of central Florida, Orlando, and a natural site near Apopka, Florida. On the UCF campus, artificial cavities were buried at predetermined depths. At the Apopka site, several suspected cavity locations were chosen for investigation. Both GPR and resistivity methods exhibit excellent capabilities in the detection of subsurface cavities in sandy soils with underlying limestones. GPR can quickly and clearly detect cavities to 70 feet deep. Resistivity has deeper penetration capabilities, yet surveys and interpretations are time consuming. Preliminary interpretations can be made during resistivity and GPR surveys. Seismic surveys failed to detect smaller cavities but can provide more information regarding subsurface stratification