Failure Mode Characteristic of Rocks Containing a Weak Interlayer with Different Thickness and Dip Angles Based on Discrete-Element Method

Abstract

Both the integrity and the strength of a rock mass are influenced by weak interlayers. In order to study the failure modes of a rock mass with a weak interlayer under uniaxial compression load, based on the discrete-element method, in this paper, a rock mass with different thicknesses and dip angles of a weak interlayer was constructed for uniaxial compression simulation by using particle flow code 2D (PFC2D version 5.00.25). The simulation results showed that cracks mostly distributed in the interlayer. Models with 0° and 15° interlayers bulged outward along the inclination of the interlayer at the interlayer, while the slip failure at the interlayer was the main cause of failure of the interlayer at 30°, 45°, and 60°. The model with a 90° interlayer was dominated by split damage, with cracks distributed randomly in the rock matrix and the interlayer. Combining the number and distribution of cracks in the interlayer with the deterioration of the rock mass strength after failure, the index of interlayer crack failure was defined, based on which the failure modes were categorized into three types: material failure, combination failure, and structural plane failure. The results of the failure mode classification of the test and simulation based on this index were similar. The index reveals the relationship between the deterioration of the rock mass strength after failure and the percentage of interlayer fractures and failure modes. This study offers a novel perspective and a scientific foundation for the quantitative classification of rock failure modes, thereby providing guidance for the stability assessment of rock structures in engineering applications.