Acoustic radar for the detection of disturbances ahead of the mining face
These studies concern the theory of elasticity in relation to problems of propagation and excitation of acoustic waves guided by and in a coal seam. Emphasis is placed on horizontal shear (SH) waves, which are used in seismic impulses and acoustic radar. The results of theoretical studies are used to obtain an approximation of the load impedance for the real geometry, which consists of a horizontal axis cylinder to be inserted in a bore hole in the layer, rotated around a vertical axis. An SH-wave generator was designed with piezo-electric transducers; results showed that electrodynamic transducers were unsuitable. The experimental study confirmed the results of the theoretical studies. The behaviour of waves at high frequencies, above 1 kHz, showed that beyond a critical frequency, the attenuation was not an increasing monotone function of the frequency, but diminished. These studies demonstrate the value of using acoustic radar for the analysis of propagation phenomena and to detect disturbances in exploitable coal seams.
Bibliographic Reference: EUR 12086 FR (1989) MF, 300 pp., ECU 16, blow-up copy ECU 37.50
Record Number: 198910978 / Last updated on: 1994-12-01
Original language: fr
Available languages: fr