Influence of non-persistent joint aperture and inclination angle on the shear behavior and fracture mode of solid rock and concrete material

Abstract

Non-persistent joints or cracks are ubiquitous in both solid rock and concrete material. Numerous experimental and numerical studies have been conducted to study the influence of geometric properties (e.g., location, connectivity, number and length) of non-persistent joint on the mechanical characteristics of rock, but few focus on the effect of joint or crack aperture. In this study, PFC 2D numerical simulation is performed to study the influence of embedded joint aperture, joint inclination angle and normal stress on the shear behavior and fracturing modes of solid rock and concrete material. The results show that the aperture has a great impact on the mechanical behavior and fracturing process of rock and concrete, and the influence varies with the joint inclination angle and normal stress. There are usually two peaks on the shear stress curves, and the peak shear strength, the damage zone width and the total crack number all decrease with increasing joint apertures. For the specimen with the same joint aperture but of different inclination angles (−30°, 0° and 30°), the peak shear strength and shear modulus are the largest at an inclination angle of 30°, and the smallest at −30°. The damage extent and degree of the intact rock bridges is closely associated with the variation of the peak shear strength for the specimens with different joint inclination angles, which are caused by the different relative positions between the embedded joint and the shear direction. Furthermore, a higher normal stress leads to a larger width of the shear damage zone for all the joints and an earlier mobilization of the second peak shear strength for the joints with −30° inclination angle.