Abstract: In order to study the pull-out bearing characteristics and interfacial stress distribution of anchorage system un der different anchorage agent thicknesses,the interface tri-linear bond-slip model was introduced to improve the constitutive re lation of interface in FLAC3D,and the effectiveness of the improved model was verified by pull-out test.By using the improved model,numerical simulation tests of bolt pulling under different thickness of mortar anchor are carried out,and the mechanical properties of bolt anchoring under different thickness of mortar anchor are analyzed.The results show that the thickness of an chorage agent has a significant effect on the shear stress distribution at the anchorage interface and the ultimate bearing capaci ty of the anchorage system,and appropriately increasing the thickness of anchorage agent can improve the ultimate bearing ca pacity of the anchorage system.With the increase of the thickness of anchoring agent,the shear stress of the interface between anchoring agent and surrounding rock increases gradually,and the shear stress of the interface between anchoring agent and surrounding rock decreases gradually.The increase of the thickness of anchoring agent leads to the transformation of the failure mode of the anchoring system from the interface failure of anchoring agent and surrounding rock to the interface failure of an choring agent.Under pull-out load,the shear stress of interface between bolt and anchorage agent and interface between anchor age agent and surrounding rock is non-uniform.The study results can provide useful reference for the design of bolt parameters.

Key words: rock bolting,bond-slip,thickness of anchorage agent,bearing characteristics,numerical simulation