Study On Anchorage Properties Of Different Anchorage Length

Bolts are important component of support of the roadway stability control.However,due to anchoring the project itself full of the complexity and diversity, leading to the current anchor design theory and calculation methods are not perfect. As an important means of detecting bolts anchoring capability, pullout tests have been widely used in support of mine. Based on the laboratory pullout tests, this thesis studied the force characteristics of different lengths of the anchoring segments, anchoring interface mechanical model and the surrounding rock stress.Determine the form of force transmitting of bolt, based on the shear-displacement model and the theoretical analysis of Kelvin model about the load distribution in the elastic deformation stage of the bolt, have got the shear stress and axial force numerical analysis types. Comparison of the shear stress and the axial force distribution trends of the anchoring segment, the shear-displacement model is more in line with the actual site.By the two methods of the numerical simulation and the pullout tests to analysis the stress state of a single bolt with different anchorage length under tensile load effect, the results show(1) Bolt failure exists two damage forms: slip failure along the interface and bolt fracture failure. When the bolt fracture failure exists three stages of deformation: elastic deformation stage, yield stage and strengthening stage, the longer anchor length, anchor the smaller deformation.(2) Bolt axial stress and interfacial shear stress distribution is non-uniform, having a better fitting between test results and theoretical analysis.(3) Different bolt failure forms have difference stress distribution of surrounding rock, there are when elastic stage and not slip occurs, concrete performance for compression state, when sliding failure occurs, the concrete stress is in tensile, when fracture failure happens, most parts of concrete is in compression.(4) Points out that there is a critical anchor length of bolt, gets interfacial shear stiffness calculation method based on cut–displacement model,derives the analytical solution of the critical length and reasonable anchorage length.