Experimental study on shear failure modes and acoustic emission characteristics of rock-like materials containing embedded 3D flaw

In nature, rock mass usually contains natural defects, which affect the mechanical properties of rock mass. At the same time, the failure of rock mass is often accompanied by shear failure behavior. Therefore, it is great sig-nificance to monitor and predict the shear failure process of fractured rock mass in order to ensure the stability of structure and the safety of construction. In this study, a method for making rock-like samples containing embedded 3D flaw is proposed and a series of shear tests are carried out under different normal stresses. The test results show that the complex shear stress-shear displacement curve can be divided into four stages. The shear strength, residual strength and shear modulus of the specimens are affected by the flaw dip angle and normal stress. The tensile failure mode is more likely to occur in low stress and small flaw angle specimens, while the shear failure mode mainly occurs in high stress specimens. A sudden increase in AE counts, AE event rates, and a sudden decrease in b-value to a minimum are usually precursors to rock failure. The RA/AF value can accurately reflect the classification and development of rock tension shear cracks. Through the Kernel density estimation (KDE) analysis on the distribution of AE events, the damage locations of rock-like in each stage are effectively identified. The movement of the maximum density point is consistent with the rock crack propagation tendency, almost following the uniform diffusion of the specimens from the middle to the end.

Automated summary

This study proposes a method for making rock-like samples containing embedded 3D flaws, and conducts a series of shear tests under different normal stresses. The test results show that the complex shear stress-shear displacement curve can be divided into four stages. The shear strength, residual strength, and shear modulus of the specimens are affected by the flaw dip angle and normal stress. Tensile failure is more likely to occur in low stress and small flaw angle specimens, while shear failure mainly occurs in high stress specimens. A sudden increase in AE counts, AE event rates, and a sudden decrease in b-value are usually precursors to rock failure. The RA/AF value can accurately reflect the classification and development of rock tension shear cracks. Damage locations of rock-like specimens in each stage are effectively identified through Kernel density estimation (KDE) analysis on the distribution of AE events. The movement of the maximum density point is consistent with the tendency of rock crack propagation, almost following the uniform diffusion of the specimens from the middle to the end.