Acoustic emission characteristics of cracked sandstones affected by different rotating angles of loading under splitting tests

At present, whether the acoustic emission possesses directionality or not is still inconclusive. Besides, the influences of cracks on the acoustic emission directionality are not intensively studied. The cleavage experiments are respectively carried out at rotating angles of 5°, 10°, 15°, 35° and 60° by using the intact disc sandstone and disc sandstone containing a prefabricated crack. The acoustic emission characteristics of the complete sandstone and the prefabricated cracked sandstone under different loading rotating angles are compared and analyzed. The results show: (1) The difference of rotating angles has an effect on the Kaiser effect of acoustic emission of sandstone. With the increase of rotating angles, the Kaiser effect of acoustic emission of sandstone gradually blurs until it disappears, verifying that the directionality of acoustic emission of rock becomes more obvious with the increase of rotating angle in this experimental condition. (2) The Kaiser effect directionality of cracked sandstone is more obvious than that of intact sandstone, for the Kaiser effect disappears faster in cracked sandstone than in the intact sandstone in the process of rotating. The results of the study can provide experimental proofs for the feasibility and accuracy of using the Kaiser effect to measure geostress.