Supporting Stress Analysis of Pre‐Tensioned Rock Bolts in Tunnels Considering the Effects of Installation Angles

ABSTRACT Rock bolts are commonly used to stabilize surrounding rocks in deep underground excavations, such as mines, tunnels, and underground caves. In actual underground projects, it is common to form an oblique angle between the installed rock bolt and the surrounding rock surface, owing to the design parameters, construction quality, or rough excavation contour. Currently, studies on the mechanical characteristics of inclined rock bolts remain relatively limited. In this study, non‐fully anchored rock bolts are investigated, and an analytical model is presented for the surrounding rock supported by a bolt installed at any angle. In this model, the supporting effect produced by the rock bolt on the surrounding rock was considered to originate from the interfacial adhesion at the anchored part and uniform pressure at the bolt plate. Theoretical analytical solutions for the bolt stress and supporting stress within the surrounding rock were derived by applying elasticity theory to the model. The effectiveness of the proposed theoretical method was verified by comparing it with numerical simulations and experimental test results from previous studies. The effects of the bolt angle, pretension force, anchor length, deployment pattern, and rock parameters on the supporting stress distribution characteristics of the surrounding rock were analyzed. For the first time, this study determines the support effect of inclined rock bolts and provides a theoretical basis for the optimization of bolt deployment and the selection of support parameters in tunnels.