Investigation on the pull-out bearing characteristics of bolts with different bond lengths

Bond length is one of the key factors affecting the bearing performance of rock bolts. It is of great significance to study the pull-out bearing characteristics of bolts with different bond length for the design of bolt support. For this purpose,based on the ''trilinear'' bond-slip model of the anchoring interface,the FLAC^3D numerical software was used to study the pull-out bearing characteristics of bolts with different bond length. The research results show that the bond length significantly affects the shape and development process of the pull-out load-displacement curve of a bolt. Increasing the bond length can improve the bearing capacity of the bolt and enhance its ability to resist failure. With the increase of the bond length,the peak pull-out load of the bolt first increases rapidly and then steadily. The softening load and friction load of the bolt increase first and then remain unchanged. There is a critical bond length of the bolt. Under the pull-out load,the axial force of the bolt gradually decreases along the length of the bolt,the peak shear stress first appears at the loading end of the bolt and gradually moves to the free end of the bolt. With the increase of the bond length,the range of the bolt axial force increases and so does the unevenness of the bolt shear stress. The research results may provide a useful reference for the design of bolt support.