Abstract: In fully grouted bolt systems for roadway rock support, rod yielding and interface slip failure pose critical challenges. To investigate stress transfer mechanisms under these failure modes, we developed a bolt-rock interaction model incorporating surrounding rock deformation and rod loading boundary conditions. We derived analytical expressions describing axial force and shear stress distributions along the rod under support equilibrium conditions. By integrating the rod’s stress-strain constitutive model with a trilinear bond-slip model, we analyzed stress distribution patterns caused by rod yielding and interface slip during surrounding rock deformation. The theoretical framework was validated through comparison with field monitoring data from a representative tunnel project. The analytical results indicate: 1) Initial yielding occurs preferentially at the neutral point. Subsequent to yielding progression, both axial force and interfacial shear stress stabilize, forming a distinct yielding platform in the axial force distribution profile. This mechanical transition converts the neutral point into an extended “neutral segment” along the rod axis. Yielding deformation magnitude exhibits positive correlations with surrounding rock strain, anchor length, and bearing plate reaction forces. 2) Interfacial slip initiates at the loading end and propagates distally through progressive softening and debonding mechanisms. Enhanced rock deformation and extended rod length markedly expand the interfacial slip zone, consequently reducing constraint effectiveness on rock mass displacement. Interfacial degradation can be mitigated through two key measures: optimizing interfacial shear strength parameters, and strategic installation of bearing plates. These findings offer critical insights for mechanized analysis and performance-based parameter optimization in fully grouted bolt support systems.

Key words: fully grouted rock bolt, surrounding rock deformation, rod yielding, softening and debonding, stress characteristics