Mechanical Properties and Acoustic Emission Evolution of Layered Shale under Triaxial Compression
To explore the mechanical properties and failure modes of shale under stress conditions at different depths,the MTS 815 rock mechanics testing system was used to conduct acoustic emission tests on shale under conventional triaxial loading.The test results show that peak stress,peak axial strain,modulus of elasticity,and Poisson's ratio are proportional to the confining pressure in the shale compression test with 60° bedding angle.The theoretical value of rupture azimuth of 60° laminated shale used under Mohr-Coulomb criterion is near 62°,the experimental value is slightly larger than the theoretical value,and the whole fluctuates narrowly near 62°,and the rupture mode of shale is the shear damage along the weak face.The change of transverse strain coefficient of shale specimen is related to the expansion characteristic.At 10 MPa,the volume strain of specimen continues to increase,and the rock volume shrinks.At 60 MPa,the volume strain of specimen reaches-0.31％,the rock volume expands.The larger the circumferential pressure is,the more significant the expansion characteristic of the specimen is.The number of shale acoustic emission localisation points has good consistency with the ringing count rate and energy rate.The total number of cumulative counts and localisation points show a decreasing trend with the increase of the enclosure pressure,and the maximum energy rate and cumulative energy decrease with the increase of the enclosure pressure.
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