Effect of bedding plane strength on the bending fracture behaviour of soft-hard interbedded rock layers

Bending fracture is a dominant failure pattern of soft-hard interbedded rock layers (SHIRLs). This study investigated the influence of bedding plane strength on the bending fracture behavior of SHIRLs using three-point-bending (TPB) tests and digital image correlation (DIC) technology. The test results indicate that the higher bedding plane strength reduces the dispersion of load-displacement curves, fracture displacement, fracture load and failure patterns. Specifically, in SHIRLs with strong bedding planes, the fracture load increases linearly with bedding plane strength, whereas the fracture displacement decreases linearly. In these cases, the instantaneous length of the main crack is approximately half of the sample. Conversely, in SHIRLs with weak bedding planes, the load-displacement curves, fracture displacement, fracture load and instantaneous crack length all exhibit significant dispersion. Particle flow code (PFC2D) is an effective numerical analysis method for exploring the bending fracture behavior of SHIRL under TPB test. Numerical simulation results further show that the bedding plane strength have significant impact on the fracture load, failure pattern and the proportion of tensile versus shear cracks. The findings of this study can provide theoretical reference and guidance for the reinforcement of SHIRLs.