Analysis Of Bolt Damage And Crack Inhibition Effect And Shear Slip Model Of Anchorage Interface

By summarizing the relevant research results,it is found that the application of bolt support in rock engineering is essentially to make the bolt(cable)interact with all kinds of cracks.It is mainly reflected in the following aspects:(1)the bolt can inhibit the initiation and development of microcracks in surrounding rock to a certain extent.(2)Anchoring in slope treatment engineering can prevent the instability and expansion of existing cracks and inhibit the initiation and development of micro cracks in bending deformation.(3)Under the action of pull-out force,the micro crack initiation and development of bolt anchorage interface.However,the analytical research on the interaction between bolt and fracture in rock engineering is not yet fully mature,so the Damage and fracture mechanics theoretical and empirical research is carried out(1)On the basis of previous studies,the analytical solutions of end anchorage and full-length anchorage of circular cavern considering the damage of surrounding rock during excavation and unloading are derived.Parameter analysis shows that when the anchorage end of the bolt enters the plastic zone,increasing the length of the bolt does not significantly improve the supporting effect.When the length of the bolt is enough,reducing the bolt spacing is more effective than increasing the bolt angle.(2)Combined with damage mechanics,it can reflect the process that the shear stiffness of surrounding rock changes gradually with the radial depth of surrounding rock in the plastic zone,which breaks through the obstacle that the shear stiffness of surrounding rock is assumed to be a constant in the plastic zone in previous studies,and improves the stress model of full-length anchored bolt in underground engineering.Through the analysis of an example,it is concluded that considering the damage of surrounding rock,the axial force of the full-length bolt will be greater than that assumed by predecessors that the rock mass is ideal elastic-plastic under the same condition.(3)Combined with the surrounding rock damage and according to the anchoring force,the bolt is simply equivalent to all kinds of constraints,and the shotcrete layer is equivalent to beam for analysis.Through the analysis of engineering cases,it is concluded that the size of the anchoring force is the key to maintain the stability of the roadway.However,when the damage of surrounding rock in plastic zone is large,the strength of surrounding rock after reinforcement is still less than that when the damage degree of surrounding rock is low,even if the bolt shotcrete support can play a strong supporting effect.(4)Based on the weight function theory,an expression of stress intensity factor of edge crack under the action of concentrated force is put forward,which is used in the analysis of anchorage crack arrest of key tension crack and main control structural plane of dangerous rock.Combining with the engineering case,the paper analyzes and demonstrates the anchoring crack stopping effect and the availability of the method,and expounds that the mechanism of the anchoring crack stopping effect is to reduce the stress intensity factor of the crack through the anchoring force,and increase the fracture toughness of the rock in a disguised form.In this paper,damage mechanics is introduced to analyze the effect of anchor cable on the bending instability of plate crack structure slope.