Experimental Investigation on Strength and Failure Characteristics of Composite Rock in Contact Zone under Biaxial Compression
摘要
The composite rock in the contact zone has unique mechanical characteristics, and the contact interface of different rocks is the main location where failure occurs in the roadway. Biaxial compression tests under different interface inclination angles, intermediate principal stresses, and mechanical differences were carried out. Combining acoustic emission (AE) and digital image correlation (DIC) technology, the strength, deformation, and fracture characteristics of the composite specimens were analyzed, and the formation and influence mechanism of uncoordinated deformation between different materials were revealed. The results show that the strength σp, peak strain εp, σci and σcd of the composite specimen increase with the increase of σ2. When the inclination angle is 60°, the change of mechanical parameters is more sensitive to σ2. Increasing σ2 will increase the pre-peak plastic deformation of the composite specimen and lead to post-peak ductility. This is because under different conditions, the pre-peak deformation and fracture degree of strong and weak materials are different, which in turn affects the post-peak bearing capacity. Increasing the interface inclination angle or reducing the degree of mechanical difference will weaken the influence of σ2. The coordination of the loading, deformation and fracture characteristics of strong and weak materials changes with the change of the interface inclination angle, thus forming three failure control modes. The uncoordinated deformation weakens with the increase of the interface inclination angle and increases with the increase of σ2. The stress-dependent deformation along the σ3 direction will aggravate the uncoordinated deformation and fracture. In engineering, uncoordinated deformation and fracture may occur in any direction parallel to the contact interface.