Analysis of mechanical properties and acoustic emission signals of sandstone with en echelon fracture under uniaxial compression

We conducted a uniaxial compression experiment using a combination of acoustic emission (AE) and digital image correlation (DIC) real-time monitoring to determine the influence of changes in the inclination angle of a double crack with a prefabricated echelon and rock bridge on the mechanical properties and AE signals of sandstone under uniaxial compression. The deterioration of the sample was most significant when the crack inclination was 30°, and that the elastic modulus and peak stress reached a minimum when the rock bridge inclination was 60°. The prefabricated cracks influenced the variation in the AE signals. The combined effect of the rock bridge and fracture inclination angles complicates the rock fracture process, resulting in different changes in the ringing counts and energy release speeds. Normalising the cumulative energy and cumulative ringing count demonstrated that the ringing count primarily reflected the accumulation of damage events and that the energy largely reflected the intensity characteristics of AE events. Finally, a rock-like damage variable expression that fully reflects the damage evolution process of the sample was obtained based on the damage variables of the acoustic generation energy characteristics combined with the probability density function conforming to the Weibull distribution.