Experimental Study on the Shear Deformation Characteristics and Mechanical Properties of Bolted Joints

Because of its simplicity, cost-effectiveness, and high efficiency, bolt-anchoring technology has been widely used in various fields such as tunnel and slope engineering. In this study, the mechanical behavior and damage pattern of bolted joints are investigated by a direct shear test of bolted joints, considering different bolt numbers, anchoring angles, and arrangements. The results showed that there are five distinct stages in the shear stress–displacement curve of the bolted joint, namely, the compaction deformation stage, the elastic deformation stage, the separation and drop stage, the yield damage stage, and the residual deformation stage. An increase in the bolt number increased the elastic modulus and shear strength of the bolted joint, although the yield deformation of the bolted mass first increased and then decreased. An increase in the anchoring angle caused the shear strength of the bolted joint to first increase and then decrease. The optimal anchoring angle was approximately 45°, and the safety factor was higher under large anchoring angles than under small anchoring angles. In particular, multiple rows of widely spaced bolts arranged perpendicular to the shear direction had significantly higher shear strength than a single row of narrowly spaced bolts placed parallel to the shear direction. These findings offer a guideline for the design of bolted rock mass in engineering projects.