Abstract: Rock bolts have been widely used as the reinforcement of jointed rock mass. To explore the shear behaviors of bolted rock joints, the influences of two locking modes, i.e., two-end locking and no-locking, on the shear characteristics of bolted rock joints were studied based on the indoor direct shear tests. The enhancement of the shear strength of the bolted rock joints influenced by normal stress and prestress was analyzed. During the test, the variation laws of the axial forces at varying monitoring points of the bolt were recorded by strain gauges, and the axial force mechanism of the bolt under different locking modes was studied. The deformation characteristics of the bolt after shear test were carefully examined and the influence of normal stress on the bending deformation of the bolt was analyzed. The results show that the shear stress-displacement curves of the locking bolted joints at both ends can be divided into three stages, i.e., the initial elastic stage, elastoplastic stage and plastic hardening stage. The shear stress-displacement curves of the unlocked bolted joints can be divided into three stages, i.e., the initial elastic stage, elastoplastic stage and plastic softening stage. The locking mode has a significant impact on the shear strength and the axial deformation of bolt. Compared with the no-locking mode, the lock at both ends is more conducive to the shear resistance. Based on the analysis of the plastic hinge position of bolt after shear test, it shows that the normal stress has an important influence on the plastic hinge position, and the distance between the plastic hinge points decreases with the increase in the normal stress. Finally, an analytical model was proposed to predict the position of the plastic hinge. The new model takes into account the influence of the normal stress, which agrees well with the experimental results.

Key words: bolt, bolted joint, shear properties, locking mode, plastic hinge, shear test