Acoustic emission characteristics of pre-cracked specimens under biaxial compression

This paper presents an experimental study in which molded gypsum pre-cracked specimens with two types of flaw (single and X-shaped cross flaws) were tested under biaxial compression. Results show that acoustic emission (AE) energy rate curves can be divided into three different periods during uniaxial compression, which correspond to crack closure, linear elastic and unstable failure stages of specimens. However, only two periods are observed during biaxial compression, which correspond to linear elastic deformation and unstable failure. Furthermore, two proposed AE parameters, namely the AE energy ratio and AE energy release ratio, and a classical AE parameter b-value were used to analyze the influence of biaxial compression loading on AE energy, respectively. With increasing confining pressure, the AE energy release ratio, as well as AE b-value decreases gradually while AE energy ratio increases. Moreover, maximum and average AE energy rate values decrease as confining pressure increases. Data presented herein is useful to study the AE characteristics of pre-cracked specimens under biaxial compression.