Mechanical Behaviors and Fracture Characteristics of Sandstone Combinations with Different Pre-crack Angles

Abstract

Layered rock masses contain many pre-existing defects, and investigating their failure mechanism is crucial for controlling layered rock mass instability. In order to understand the layered rock fracture mechanism, this study develops sandstone combination models containing cracks of different angles using the Particle Flow Code software (PFC2D) to conduct the uniaxial loading tests. In addition, it analyzes the mechanical properties and fracture characteristics of the models. The pre-crack angles and the composite materials determine the mechanical properties and crack propagation of the sandstone combination (SC) models. The results indicated that the peak stress and elastic modulus of the SC models increase as the pre-crack angle rises. The force chain concentration and the crack initiation location change with the different pre-crack angles, and the initiation stress improves gradually. The entire acoustic emission (AE) process is divided into three phases per axial stress and AE event number. The AE active level significantly correlates with the pre-crack angle change. The “V” type trend is shown in the crack number distribution, and the tensile crack is the predominant mode with some shear cracks. The micro-crack concentration and macroscopic damage zones are more prevalent in the low-strength parts, and the pre-crack angles define the influence weight of the pre-crack angle and the composite material strength.