To investigate the failure of non-continuous jointed rocks under compression loading, many researchers have performed uniaxial and biaxial compression tests. In this paper, I simulated numerically the behavior of artificial jointed rock under axial loading and compared it with laboratory experiments. The numerical model in this paper uses Mohr-Coulomb shear strength criterion with parameters of cohesion, friction, and tensile strength as tested in the laboratory. Artificial rock samples with 75° bridge angle were tested in the laboratory under uniaxial loading until failure. Curvilinear cracks (wing crack) initiated near the joint tips and propagated toward the other inner joint tip. The numerical model showed that tensile stress concentration caused wing crack initiation due to stress flow around the pre-existing non-persistent open joints. I compared the yielding behavior of the numerical simulation - under two tensile strength failure criteria - and the laboratory tests; the results showed significant agreement between the two tests. In this all compressive load environment, tensile stress concentration originated yielding at the inner joints' tips and formed continuous yielding surfaces in the bridge area.
Intact rock masses might occur at extreme depths while near surface rock masses are jointed. These joints can be persistent in some cases such as fault. However, the majority of joints and fractures are non-persistent ones and rock bridges exist between joints and/or fractures. Usually, near surface rocks are subjected to low confinement stress and this warrants the use of uniaxial loading to understand the behavior of rock mass. Terzaghi (1962) presented a geological model for sedimentary rocks at which the joints occur parallel to each other. This study presents the development of fractures in jointed artificial rocks that simulate sandstone behavior under uniaxial loading, their fracture development and coalescence process by using the finite element method.
In nature, rock slopes are highly heterogeneous and are associated with many unknowns such as the state of the stress, the structures inside the rock mass, and the strength parameters. These three factors among others control the design of rock slopes and the failure mechanism. Rocks may fail in tension or shear, depending on the mechanism of loading and the stress path in the field or in the laboratory. Rock slopes can be divided into two main categories: structurally controlled slopes, such as the planer and wedge failures, and the non-structurally controlled slopes. The structurally controlled slopes normally fail by shear sliding along one or more continuous discontinuities whereas in the non-structurally controlled slopes, failure is a complicated process and involves failure in both the discontinuity and the intact material Terzaghi (1962).