Detection of mining hazards and geologic conditions by electromagnetic and seismic probing from boreholes
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
Similar Records
Detecting high-contrast seismic anomalies using cross-borehole probing. [Measurements at different depths between boreholes]
Detecting high-contrast seismic anomalies using cross-borehole probing
Related Subjects
01 COAL, LIGNITE, AND PEAT
CAVITIES
ELECTROMAGNETIC SURVEYS
SEISMIC SURVEYS
BOREHOLES
EXPERIMENTAL DATA
FIELD TESTS
MINING
DATA
ELECTRICAL SURVEYS
GEOPHYSICAL SURVEYS
INFORMATION
NUMERICAL DATA
SURVEYS
TESTING
580201* - Geophysics- Seismology & Tectonics- (1980-1989)
012000 - Coal
Lignite
& Peat- Mining