Mechanical Behavior of Soft Rock Roadway Reinforced with NPR Cables: A Physical Model Test and Case Study

Deep soft rock roadways are prone to large deformations and failure when reinforced with traditional rockbolts owing to the stiffness mismatch between soft rocks and rockbolts. Thus, a novel rockbolt named "negative Poisson's ratio (NPR) bolt/cable" that maintains a constant support force during loading is used to reinforce deep soft rock roadways to prevent large deformations. In this study, a large-scale physical model test was conducted to reveal the mechanical performance of NPR cables in soft rocks and obtain the mechanical properties of reinforced rock masses. The test results show that the rock mass reinforced with the NPR cable underwent progressive failure and exhibited the characteristics of a constant-resistance yielding-pressure under external loading, suggesting that NPR cables operate well with soft rock masses. Moreover, on-site investigations confirmed that the effective control of NPR cable supports slow and large deformations of soft rock roadways. An analytical model was developed to verify the physical model test results. The study findings can serve as a reference for theoretical model studies and field applications of NPR cables to prevent large deformations.