Influences of Inclined Pre-Existing Flaw on Shale Failure Modes in Uniaxial Compression Tests

Numerous studies have focused on the mechanical properties of shale specimens to support hydraulic fracturing in gas engineering. However, failure modes containing a pre-existing flaw are still not clear. A series uniaxial compression tests were conducted coupled with acoustic emission (AE) technology and high-speed camera. slow enough variable loading speed scheme (0–50 kN: 0.1 kN/s, 50–100 0.05 kN/s; 100-failure: 0.02 kN/s) is adopted allow microcracks fully develop. The damage mechanism mesoscale from moment tensor inversion AE signals cracking behaviors macroscale associated. Both bedding layers had significant influences characteristics, progressive cracking, specimens. peak stress increases fluctuated as layer angle α increases, maximum minimum values take place at α=90° α=0°, respectively. In addition, flaw, layers, field jointly control It was found that α=0° specimen failed due tension splitting, α=30° splitting shear across matrix, α=60 matrix along matrix. study can provide some references construction complex crack networks