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The existence of the weak interlayer in the roadway surrounding rock mass presents a huge threat to the stability of the underground structure and the safety of mining engineering. By the characteristics of strong adaptability, superior anchoring effect and high efficiency of construction, rock bolt has been widely applied in mine reinforcement. However, the influence of the weak interlayer on the compressive performance of the bolted rock mass is still poorly understood due to the challenges in constructing an efficient experimental platform and complex testing processes. Here, we used the self-developed test system to investigate the influence of the thickness, uniaxial compressive strength, and dip angle of the weak interlayer on the compressive behavior of the bolted rock mass with a single free surface. The results show that the weak interlayer has a great weakening effect on the peak strength and elastic modulus of the specimens due to its low mechanical properties, as well as influencing the crack distribution and failure mode of the samples. As the strength of the weak interlayer is lower than 1.27 MPa, the thickness exceeds 20 mm, and the dip angle exceeds 15°, the synergistic bearing effect will be significantly reduced and affect the mechanical performance of the specimens. The evolution of the bolt force and bending moment are greatly impacted by the deformation process which could be divided into distinct stages of destruction, thereby providing an excellent detection method for judging the stability of the surrounding rock of the mine. The discovery of this research promote a better understanding of the impact of the weak interlayer on mining engineering and guide the mine reinforcement in the future.

The widespread existence of weak interlayer poses a serious threat to the stability of roadway surrounding rock under constant stiffness restraint boundary condition in lateral direction (axial direction of roadway) and the rock bolt is widely used to reinforce the surrounding rock of roadway. So, in this paper, the reinforcement performance of the bolted rock mass with a weak interlayer was investigated under constant lateral stiffness (CLS) boundary condition. The research results indicated that the peak strength and elasticity modulus of the samples exponentially increase with the increasing of bolt pretension force and density. Two parameters Rp and RE were put forward to quantitatively describe the reinforcement effect of bolt pretension force and density on the peak strength and elasticity modulus of the samples. Under CLS boundary condition, the lateral direction of the samples experienced loading-unloading and expansion - compaction deformation periods during the whole triaxial compression process. The mechanism for the transformation of expansion - to - compaction was explained. Two new failure modes of the samples were observed and analyzed in detail, and were found them different from those of the bolted jointed rock mass and bedded rock mass.

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