Strain field evolution and crack coalescence mechanism of composite strength rock-like specimens with sawtooth interface

The mechanical behaviors of composite rock masses containing a complex interface widely distributed in nature are significantly different from those of monolithic rock masses. The objective of this study is to perform a series of uniaxial compression tests to study the influence of sawtooth interface parameters on the fracture behavior of rock-like composite specimens. Meantimes, the acoustic emission (AE) and digital image correlation (DIC) technique were used to classify damage stages and record strain field evolution, respectively. The results of this study demonstrate that stress-strain curves of composite rock-like specimens with different sawtooth interfaces display characteristics of plastic failure, friction failure characteristics and two different brittle failure charac-teristics in the post-peak phase. The peak strength of the specimen first decreases and then increases as the inclination of the interface increases, achieving the maximum value of 28.29 MPa at the inclined interface of 90 degrees. The strain concentration zone is mainly generated and expanded around the interface. The parameters of the sawtooth have a significant influence on the type and location of cracks developed along the interface. In addition, there is a strong relationship between the mode of failure of the specimen and the strength of the rock layer and the inclination of the interface. According to the relative positional relationship between the coales-cence path of the specimen and the interface, the failure modes of the specimen are classified as single weak rock layer failure (S-AB-0, S-AB-15), oblique failure through rock layer interface (S-AB-30, S-AB-45), slip failure along the interface (S-AB-60, S-AB-75) and axisymmetric failure along the interface (S-AB-90). This result is of great importance for a thorough understanding of the crack coalescence mechanism and strain field evolution of rock -like composite specimens.