Experimental and numerical investigation on the effects of bedding plane properties on the mechanical and acoustic emission characteristics of sandy mudstone

Abstract

Bedding planes have a strong influence on the mechanical characteristics of layered rocks. To study the effects of bedding plane properties on the strength, fracture and acoustic emission (AE) characteristics of rock, Brazilian tests of sandy mudstone with different angles between the bedding plane inclination and loading direction (the bedding plane-loading angle) were first conducted. Based on the cohesive zone model in ABAQUS, the effects of the number and strength of bedding plane on the fracture and crack distributions of specimens were then investigated through numerical simulation. The experimental results showed that with increasing bedding plane-loading angle, the failure strength of the disk specimens continuously increased. The characteristics of the AE count and crack distributions (RA-AF distribution) were predominantly affected by the failure pattern. The AE count distributions were divided into two types: unimodal distribution and multimodal distribution. The cracks that formed in the specimens were divided into three forms: tensile cracks, mixed cracks and shear cracks. The numerical simulation results showed that both the number and strength of the bedding planes strongly influence the fracture and crack distributions of specimens. With the increase in bedding plane strength, the failure patterns of the specimens under each bedding plane-loading angle transformed from layer activation failure to central failure under each bedding plane-loading angle tested. Furthermore, under each bedding plane-loading angle, the failure patterns of specimens with different numbers of bedding plane were the same, and the percentage of cracks on the bedding planes increased while the percentage of cracks within the rock matrix decreased.