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| An experimental study of ultrasonic anisotropy of coal under uniaxial loading |
| ZHAO Yu1, ZHANG Yu-Gui2, ZHOU Jun-Yi2 |
1.School of Civil Engineering,Henan Polytechnic University,Jiaozuo 454000,China;
2.College of Safety Science and Engineering,Henan Polytechnic University,Jiaozuo 454000,China |
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Abstract In the study of coal rock elastic wave response characteristics,the influence of axial compression on longitudinal wave,transverse wave velocity and attenuation has not been given enough comprehensive consideration.In view of such a situation,three kinds of coal samples which experienced different grades of metamorphism were chosen from the Pingdingshan No.8 mine.Vertical-bedding samples,parallel-bedding and vertical-face cleat samples,parallel-bedding and vertical-butt cleat samples were prepared to conduct water absorption and ultrasonic experiment.Some experimental results have been obtained:First,in the natural state,longitudinal,transverse wave velocity and quality factor in three directions of the three kinds of coal samples are anisotropic,generally longitudinal,transverse wave velocity and quality factor in two directions parallel to bedding are greater than the corresponding data perpendicular to bedding plane.Second,in the coal rock,the longitudinal and transverse wave velocity increases rapidly with the increase of axial pressure in the early stages.After that,the velocity increases slowly and the wave velocity decreases rapidly until the coal sample is destroyed,the transverse wave velocity is not as obvious as the longitudinal wave.Third,in the three directions,the quality factor increases firstly and then decreases with the increase of stress,and QS is generally larger than that of QP.Fourth,in coal samples of different metamorphic grades,longitudinal,transverse wave velocity and quality factor differences are more obvious,longitudinal,transverse wave velocity of 1/3 coke is greater than that of coking coal and that of the fat coal.
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Received: 25 July 2016
Published: 10 April 2017
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