Acoustic Emission and Electromagnetic Radiation of Rock under Combined Compression-Shear Loading

This paper reports the use of inclined sandstone specimen in the uniaxial compression tests to achieve the combined compression and shear loading (CCSL) state. A series of CCSL tests are performed on the inclined specimens with an inclination angle of 0°, 3°, 5°, and 7°. Acoustic emission (AE) and electromagnetic radiation (EMR) during the failure process are monitored. The results show that the additional shear stress component caused by the inclined shape configuration of tested specimens has significant effects on the failure mode and mechanical properties. The increase of inclination causes the failure mode to transit from the axial splitting to shear failure, and decreases the peak strength and elastic modulus of the inclined specimens. The specimen inclination lowers the damage prior to the peak stress, but stimulates the damage development after the peak stress. EMR has better correlation with stress drop than AE. The 65% of the peak strength is defined as the stress threshold of rock failure. The inclination angle lowers stress threshold of rock failure and accelerates failure initiation