Analysis of stress distribution characteristics of fully anchored bolt based on actual surrounding rock deformation

During the fully anchored bolt support process,the interaction between the anchored bolt and the surrounding rock will cause the stress distribution of the bolt to change. In order to explore the stress distribution of the bolt in the normal support process and critical failed support process,the interaction model of the anchored bolt-surrounding rock is established based on the deformation of surrounding rock. The analytical expressions of axial force and shear stress along the length of the bolt during the normal support process and critical failed support process are derived. Furthermore,the distribution curves of axial force and shear stress along the length of the bolt are obtained. Also,the effects of rock condi- tion,anchor length and anchorage force on the stress distribution of fully anchored bolt are analyzed under the condition of anchorage parameters such as anchorage modulus,anchorage and anchorage cross-sectional area. The results show that during the normal support of the full-length anchor bolt,the stress distribution of the rod conforms to the neutral point theory. The factors affecting the axial force and shear stress distribution of the anchor include surrounding rock condi- tions,anchoring parameters and anchoring forces. During the normal support process,the stress distribution of the full- length anchor bolt body conforms to the neutral point theory. As the surrounding rock becomes soft,the anchor rod moves to the orifice direction and the axial force and shear stress increase. Large anchoring force affects the stress distribution of the rod,the greater the anchoring force,the more uneven the axial force distribution,and the smaller the shear stress from the orifice to the neutral point,the greater the shear stress from the neutral point to the rod end. Therefore,in the actual project,the bolt anchoring force can be monitored in real time. The theoretical basis of this paper can reveal the force characteristics during the bolt support process. In the bolt support critical failure,the harder the surrounding rock, the larger the shear stress and the axial force and the more concentrated the distribution is. The length of the anchor af- fects the support performance of the full-length anchor bolt,but the increase of the bolt length after the bolt length ex- ceeds a certain range doesn’t significantly improve the anchoring effect of the anchor.