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Title: Cavity detection and delineation research. Report 2, Seismic methodology, Medford Cave Site, Florida
Authors: Curro, Joseph R.
Keywords: Cavity detection
Constant-spacing method
Crosshole seismic
Seismic techniques
Surface refraction
Geophysical research
Medford Cave, Florida
Seismic waves
Publisher: Geotechnical Laboratory (U.S.)
Engineer Research and Development Center (U.S.)
Series/Report no.: Technical report (U.S. Army Engineer Waterways Experiment Station) ; no. GL-83-1 rept. 2.
Description: Technical Report
Abstract: As part of a research program designed to find a quick and economical methodology to detect and delineate cavities, seismic technology was applied to the cavity problem at the Medford Cave site, Florida. Six seismic techniques consisting of surface refraction, constant-spacing, fan-shooting, surface shear-wave, uphole refraction, and crosshole investigations were employed at the site in an effort to detect and delineate cavity features. The results of these tests indicated that the surface refraction, constant spacing, and crosshole techniques detected and partially delineated cavities. Their degree of success was as follows: a.) Surface Refraction Tests : Only one out of seven tests successfully detected a cavity (6 to 11 ft. high and 31 ft. wide vith the roof about 11 ft. below ground surface). Partial delineation was accomplished in that the start of the cavity was defined. b.) Constant Spacing Tests : All three of the constant-spacing surveys detected cavities which ranged in size from 5 to 8 ft. high and 4 to 13 ft. wide with the roofs being 9 to 20 ft. below the ground surface. Partial delineation was achieved in that the the cavities were located in plan but not to depth to or height of the cavities. c.) Crosshole Tests : The crosshole P-wave test conducted across a cavity indicated significantly lower velocities in the area of the cavity (14 ft. high and 9 ft. wide with the roof 19 ft. below the ground surface). It will be noted that the Crosshole technique cannot detect a cavity, per se, but will identify weak zones or low-velocity layers that may or may not be void-related. Partial delineation using the depth to and thickness of the zone of lower velocities was accomplished within 2 ft. of the cavity depth and height. Planar delineation (diameter and location of the cavity between borings) was not achieved. In summary, the constant-spacing technique is the only surface seismic test procedure recommended for use in cavity detection-delineation and the crosshole P-wave technique is the only subsurface method recommended.
Rights: Approved for public release; distribution is unlimited.
Appears in Collections:Technical Report

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