MONITORING HIDDEN COAL-ROCK INTERFACE

PCT No. PCT/SU86/00121 Sec. 371 Date Jul. 25, 1988 Sec. 102(e) Date Jul. 25, 1988 PCT Filed Dec. 25, 1986 PCT Pub. No. WO88/05116 PCT Pub. Date Jul. 14, 1988.A method for monitoring a hidden coal-rock interface, comprising the steps of irradiating the medium (M) being monitored from a gamma-ray source (1) and registering by a detector (2) the intensity of backward scattered radiation at a distance (A) from the surface of the medium (M) and at a distance (B) from the radiation source (B). Two zones (Z1 and Z2) are formed at the detector (2) for reception of backward scattered radiation, differently spaced from the source (1), so that the intensity of backward scattered radiation received by the zone (Z1) closer to the source (1) diminished with the distance (A) from the detector (2) to the medium (M), and grows when received by the zone (Z2) far from the source (1). The intensities of backward scattered radiation of both zones (Z1 and Z2) are summed up to obtain total intensity invariant with respect to variations of the distance (A) between the detector (2) and the medium (M). A transducer realizing the above method comprises a housing accomodating the gamma-ray source (1) and backward scattered radiation detector (2) shielded by a screen (3) provided with ports at different distances from the source (1). The area of the port farther from the source (1) is greater than that of the nearer port; the distance (B) from the gamma-ray source (1) to the detector (2) does not exceed a preset maximum distance (A2) from the detector (2) to the medium (M) being monitored.