Geophysical Hazard Detection from the Working Face.
Suhler SA; Owen TE; Duff BM; Spiegel RJ
NTIS: PB/83-191742 :234 pages
The objective of this project was to define and demonstrate the feasibility of remotely sensing abandonded mine workings from underground. Geophysical probing techniques based upon electrical, seismic, and electromagnetic methods were evaluated; the seismic method was determined to be the most favorable. Guided seismic wave propagation in coal seams offered the potential of detecting inundation hazards 200 ft or more ahead of mining. Controlled waveform seismic source transducers and specialized receiving transducers were developed with emphasis on concept demonstration and experimental guided wave propagation studies. Two major field tests were undertaken in Kentucky and Virginia. Guided wave propagation phenomena were observed in 54- and 70-in coal seams. Normal mode love waves and rayleigh-type guided waves were generated by the controlled-source transducers and by hammer blows on a steel anvil attached to the coal. Numerical evaluations of theoretical velocity dispersion characteristics of both love and rayleigh-type waves were confirmed in the experimental test results.
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