Abstract: The joint surface or discontinuous surface widely existing in the rock mass has obvious transverse shear effect on the anchor rod,which makes the anchor rod show the failure characteristics of tension shear or tension bending.Based on the interaction characteristics of bolt and layered rock mass,the direct shear test of anchored joints was carried out.The concrete block with the size of 400 mm×400 mm×400 mm was used to simulate the surrounding rock.The deformation of the bolt with a diameter of 12 mm at different anchoring angles was studied.The strain gauge was used to monitor the strain change process during the shear process of the bolt.The deformation characteristics and evolution process of the bolt under shear action were analyzed,and the deformation mechanism of the bolt in different stages was revealed.It is found that there are three different stages of stress-deformation of anchored joint surface under shear action,which are elastic stage,plastic strengthening stage and failure stage.In the elastic stage,the bolt near the joint surface is dominated by bending deformation,and the axial tensile ca pacity of the bolt has not been effectively exerted.In the plastic strengthening stage,the bolt near the joint surface has a ben ding angle of 21°~55° compared to the original axial direction due to different anchoring angles,and is mainly tensile.The fail ure stage corresponds to the necking phenomenon of the steel bar when the anchor reaches its tensile limit.Under the action of shearing,the maximum curvature section will be formed on the bolt section corresponding to the boundary between the broken zone and the complete zone of the anchorage grouting body,and the transverse shear deformation of the bolts on both sides of the section is distributed in a broken line.The deformation of the bolt caused by the plastic strengthening stage of the anchored jointed rock mass mainly occurs in the section between the maximum curvature section and the intersection of the bolt and the joint surface.The research results can provide reference for the establishment or correction of the anchorage model of jointed rock mass.

Key words: fully-grouted bolt,jointed rock mass,shear test,strain monitoring,deformation characteristics