An experimental study of mechanical behavior of brittle rock-like specimens with multi-non-persistent joints under uniaxial compression and damage analysis

The mechanical behavior of jointed rock masses significantly affects the stability of rock engineering applications. In this paper, the peak strength, Young's modulus and failure patterns of brittle rock-like specimens with multi-non-persistent joints under uniaxial compression are investigated. The joint geometry is defined by four factors: joint angle, spacing, joint length, and rock bridge length. The experiment results show that the joint angle has the greatest influence on the peak strength and Young's modulus of specimens, followed by joint length. A damage mechanical theory is adopted which deals with some sets of joints distributed in rock masses. Based on the geometrical distribution of joints, a macro damage model which considers the influence of the normal vector and area density of joints is used to describe the joints. The peak strength and Young's modulus of jointed specimens predicted by the damage mechanics method reflect the trend of the experimental results, which proves the influence of initial geometric damage of joints on the peak strength and Young's modulus of jointed specimens. The initial geometric damage of joints is mainly induced by the joint area density. Finally, from the micro damage aspect, to analyze the damage evolution and strain softening process of jointed rock masses, a modified numerical model (damage strainsofting model) on the basis of secondary development in fast Lagrangian analysis of Continua is proposed to simulate the fracture development of jointed rock masses. The peak strengths, Young's modulus and failure modes of rock specimens with non-persistent joints under uniaxial compressions are simulated and compared with the results obtained from the lab experiments indicating that the model is capable to replicate the physical processes.