Abstract: Steeply dipping thin-layered ore bodies are prone to exhibit failure modes such as bending and breaking of the sidewall or bending and internal bulging caused by high tangential stress, which are closely related to the mechanical properties of the bedded rock mass. In order to investigate the deformation, strength properties, and failure characteristics of Sishanling layered iron ore during the shear failure process, conventional triaxial shear tests were conducted on layered rocks under various bedding dip angles and confining pressures. The test results show that the peak strength, axial displacement, circumferential deformation and failure mode of stratified iron ore samples are affected by confining pressure and layered joint angle. With an increase in the bedding angle, the shear strength of the specimen initially increases and then decreases, while the axial and circumferential deformations exhibit a ‘wave-like’ trend. Moreover, as the confining pressure increases, the peak shear strength of the specimen significantly improves, the axial shear displacement increases, and the circumferential deformation decreases. In addition, failure mode of bedding iron ore specimen is controlled by both the bedding dip angle and confining pressure. The study reveals that the failure mode is stress-controlled when the bedding dip angles are 0° and 30°. At a bedding dip angle of 45°, the specimens exhibit a stress-structure controlled failure mode, while for angles at 60° and 90°, the failure mode is predominantly controlled by the structure. Based on the test results, a failure criterion is proposed considering both the intermedium principle stress and the ore bedding angle. The test results could offer important technique support for the stope and blasting and also the ground support design.

Key words: bedding dip angle, confining pressure, strength, deformation, failure mode