Evaluation of High-Resolution Earth Resistivity Measurement Techniques for Detecting Subsurface Cavities in a Granite Environment
Final rept. 12 May-15 Dec 1975
SOUTHWEST RESEARCH INST SAN ANTONIO TX
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The purpose of this work was to experimentally explore the use of earth resistivity measurements using a pole-dipole electrode array in the detection of deep tunnels in a granite environment. Measurements both on the ground surface and in drilled holes were evaluated. Tests were conducted at two sites existing mine adits or tunnels, one at the Colorado School of Mines Experimental Mine site and one at a Gold Hill, Colorado, site. The mine adits with an approximate 10 x 10-foot 3 x 3-m cross section were successfully detected from the surface at both locations through overburden thicknesses ranging from 30 to 81 feet 9.1 to 24.7 m. Other geological features of the terrain were also identified by the measurements. Successful detection was also made from a dry borehole that was 16 feet 4.9 m horizontally displaced from the adit at the adit level. Although near surface geological features produce strong resistivity anomalies, they can be identified.
- Geology, Geochemistry and Mineralogy
- Test Facilities, Equipment and Methods