Cavity detection and delineation research. Report 3, Acoustic resonance and self-potential applications, Medford Cave and Manatee Springs Sites, Florida
Cooper, Stafford S.
Technical ReportAbstract: In this study three surface geophysical methods were applied to the problem of detecting and delineating subsurface cavities. An acoustic resonance technique was used at the Medford Cave test site in Florida where there are numerous shallow air-filled solution cavities in limestone. Sonar and self-potential (SP) methods were used at the Manatee Springs test site in Florida where waterfilled solution cavities are found at a depth of 90 ft below the ground surface. The apparatus and techniques used are described in this report. Evaluations of the methods for detection and delineation of subsurface cavities are presented. Conclusions developed in this study are as follows: a.) The acoustic resonance technique can be reasonably successful in delineating accessible air-filled cavities in limestone if feature dimensions are on the order of a few feet and they are found at depths less than about 20 ft. Features having a high degree of complexity and large (>20 ft) lateral dimensions were not accurately delineated using this technique. b.) The sonar feasibility investigation carried out at Manatee Springs demonstrated that a sonar source can be used to excite large waterfilled cavities and the host rock to distances exceeding 200 ft from the source. However, equipment and time limitations restricted the scope of this effort. The data obtained were analyzed but no clear indication of the known cavity feature could be developed. Further study of this method may be warranted. c.) The SP technique used at Manatee Sprlngs did provide useful results. water flowing in the main solution feature produced readily detectable surface SP anomalies and these data were used to crudely delineate the cavity location in plan view. This result is all that can reasonably be expected of the method considering the complexity of the feature and its depth of burial (90ft). Neither the above methods nor the self-potential method provide depth determinations.
Geotechnical Laboratory (U.S.)Engineer Research and Development Center (U.S.)
Acoustic resonance; Acoustics; Geophysical investigations; Self-potential; Sonar; Medford Cave, Florida; Manatee Springs, Florida; Sonar; Cavities (Underground); Cavity detection
Technical report (U.S. Army Engineer Waterways Experiment Station) ; no. GL-83-1 rept. 3.
Approved for public release; distribution is unlimited.