Detection of mining hazards and geologic conditions by electromagnetic and seismic probing from boreholes

Technical Report · Tue Sep 07 04:00:00 EDT 1982

OSTI ID:6720968

Buettner, H M; Laine, E F; Lytle, R J; Portnoff, M R

We tested cross-borehole probing techniques for the detection of natural and man-made cavities potentially hazardous to mining. Both electromagnetic and seismic probing techniques were tested. For electromagnetic probing of a tunnel or other regularly shaped cavity, theory predicts that two distinct signal minima defining the roof and floor will exist on the transmission side, provided that the wavelength is less than or equal to the cavity diameter. Our field tests showed a clear cavity signature (as defined by the minima) for regularly shaped cavities when the surrounding rock was competent, but a less clear signature when the rock was fractured. For seismic probing, theoretical/numerical analysis shows that as the source and receiver are lowered in boreholes straddling the anomaly, the signal minima and phase structure easily yield the anomaly's lateral and vertical positions. The analysis includes compressional waves (P waves), and horizontally and vertically polarized shear waves. Field tests showed that the first arrival amplitude for a transmitted P wave is an effective tunnel diagnostic, and that under appropriate conditions, first arrival time may also be useful. Probing with shear waves was unsuccessful because their response could not be separated from the response of the P waves. 31 references, 60 figures.

• Research Organization: Lawrence Livermore National Lab., CA (USA)
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 6720968
• Report Number(s): UCRL-15592; ON: DE84013953
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
012000 -- Coal
Lignite
& Peat-- Mining
58 GEOSCIENCES
580201* -- Geophysics-- Seismology & Tectonics-- (1980-1989)
BOREHOLES
CAVITIES
DATA
ELECTRICAL SURVEYS
ELECTROMAGNETIC SURVEYS
EXPERIMENTAL DATA
FIELD TESTS
GEOPHYSICAL SURVEYS
INFORMATION
MINING
NUMERICAL DATA
SEISMIC SURVEYS
SURVEYS
TESTING