An Experimental and Numerical Study on Mechanical Behavior of Ubiquitous-Joint Brittle Rock-Like Specimens Under Uniaxial Compression

Rock engineers often encounter materials with a large number of discontinuities that significantly influence rock stability. However, the strength and failure patterns of ubiquitous-joint rock specimens have not been examined comprehensively. In this study, the peak uniaxial compressive strength (UCS_J) and failure patterns of ubiquitous-joint rock-like specimens are investigated by combining similar material testing and numerical simulation using the two-dimensional particle flow code. The rock-like specimens are made of white cement, water, and sand. Flaws are created by inserting mica sheets into the fresh cement mortar paste. Under uniaxial compressional loading, the failure patterns of ubiquitous-joint specimens can be classified into four categories: stepped path failure, planar failure, shear-I failure, and shear-II failure. The failure pattern of the specimen depends on the joint-1 inclination angle α and the intersection angle γ between joint-1 and joint-2, while α strongly affects UCS_J. The UCS_J of specimens with γ = 15° or 30° shows similar tendencies for 0° ≤ α ≤ 75°. For specimens with γ = 45° or 60°, UCS_J increases for 0° ≤ α ≤ 30° and decreases for α > 30°. For specimens with γ = 75°, the UCS_J peaks when α = 0° and increases for 60° ≤ α ≤ 75°. The numerical and experimental results show good agreement for both the peak strength and failure patterns. These results can improve our understanding of the mechanical behavior of ubiquitous-joint rock mass and can be used to analyze the stability of rock slopes or other rock engineering cases such as tunneling construction in heavily jointed rock mass.