Experimental investigation on fracturing process of marble under biaxial compression

In this study, servo-controlled biaxial compression tests were conducted on marble specimens to investigate their failure characteristics and fracturing process. The complete stress–strain curves were obtained, and the three-dimensional (3D) features of the failure surfaces were acquired by 3D laser scanning. Acoustic emission (AE) monitoring and moment tensor (MT) analysis were used in combination to better understand the fracturing mechanism of marble under biaxial compression. It was noted that a type of 3D stepwise cracking behaviour occurred on the fracturing surfaces of the examined specimens. The stress dropped multiple times, and a repeated fracturing mode corresponding to the repeated stress drops in the post-peak regime was observed. Three substages, i.e. stress stabilisation, stress decrease and stress increase, were identified for a single fracturing mode. Then quantitative and statistical analyses of the fracturing process at each substage were discussed. Based on the testing results, it was found that at the stress stabilisation substage, the proportion of mixed-mode fractures increased. At the stress decrease substage, the proportion of mixed-mode fractures decreased, and the tensile or shear fractures increased. At the stress increase substage, the proportion of mixed-mode or tensile fractures decreased, and the shear fractures increased. Finally, a conceptual model for the stepwise crack formation was proposed.