Progressive Failure Process of Sandstone Under Different Loading Conditions via Acoustic Emission Characteristics

This study investigates the acoustic emission (AE) characteristics during sandstone failure under three typical mechanical tests:direct shear test (DST), Brazilian splitting test (BST), and uniaxial compression test (UCT). Results show a significant difference in the log-linear slope between AE count and amplitude across different tests, reflecting variations in the scaling distribution characteristics of AE signals. Peak frequency distributions vary, with DST predominantly in the 150- to 200-kHz range, BST in the 0- to 100-kHz range, and UCT showing a mixed distribution. RA (rise time/amplitude) and AF (counts/duration) analysis classified crack types, indicating shear-type signals dominate in DST, tensile-type signals in BST, and a slight dominance of tensile cracks in UCT. Shear cracks generally exhibit higher AE energy, especially in high-energy ranges (10-1000 mV*mS), whereas tensile cracks dominate the low-energy range (0.1-1 mV*mS). These findings advance the understanding of rock failure mechanisms and AE signal behavior.