摘要：The objective of the paper is bringing about an analysis of the propagation characteristics of the ultrasonic waves in the coal samples with holes of different inclination angles. With the ultrasonictime method for the experimental test, the transmission coefficient, wave velocities, and first wave amplitudes were measured and calculated, respectively. Theoretical analysis and numerical simulation are also applied in the paper. The study results revealed the following: (1) It was observed that with the increases in the inclination angles, the attenuation coefficients displayed linearly increasing trends and the transmission coefficients showed linearly decrease; (2) The longitudinal wave velocities and first wave amplitudes had decreased following the drilling of the coal samples, and the decrease rates of the first wave amplitudes were found to be larger than those of the longitudinal wave velocities; (3) When the inclination angles of the holes were 30°, and the frequency was 50 kHz, the detectable hole diameter range was within 0 to 54.6 mm when the ultrasonic waves penetrated through the coal samples containing circular holes; (4) When the inclination angles of holes were 30°, and the hole diameters were approximately 10 mm, then the attenuation coefficients were observed to increase with the increased frequencies of the ultrasonic waves. The present study results have certain potential reference values for the detection of mine gob or abandoned mine laneway using seismic or low-frequency waves.
