Mechanical Behaviour of Anchored Rock Containing Weak Interlayer under Uniaxial Compression: Laboratory Test and Coupled DEM–FEM Simulation

The reason for instability in a rock mass with a weak interlayer is not only the sliding failure of the rock interlayer structural plane but also the tip crack propagation caused by the stress concentration at the tip of the interlayer. In this study, a uniaxial compression test of an anchored rock mass with a weak interlayer was carried out to determine the influence of the anchorage on the failure pattern and the strength of samples with different interlayer dip angles. In addition, the coupled DEM–FEM numerical simulation method was used to study the internal stress evolution of the sample and the stress distribution of the anchor under the anchorage effect. The results showed that the anchorage effect on reinforcement and strength enhancement was greatest for the sample with an interlayer dip angle of 30°. Under the anchorage effect, crack initiation was limited and there was more shear failure in the samples. The reinforcement range of the anchorage effect for anchors with restrained ends was larger than for anchors with free ends. When the rock–anchor interface was unbonded, the effect of the free-ends anchor reflected the residual friction, but the restrained-ends anchor still worked by limiting the lateral expansion of the rocks. The stress values and deformation of the anchors decreased gradually with an increase in dip angle.