Load transfer law and anchorage length design at interface between rock bolts and rock mass
To reveal the failure mechanism of anchorage interface debonding of surrounding rock in roadway and quantify the design parameters of rock bolt support,theoretical derivation was made by using the trilinear bond-slip model,and the distribution and evolution law of interfacial shear stress,axial force of bolt and ultimate anchorage force at the interface during the whole process of anchorage debonding failure under axial load were studied.According to the different lengths of anchorage section,two types of interfacial shear stress distribution and evolution were obtained.The results show that when the anchorage length is short,the interfacial shear stress has a full-length softening stage and when the anchorage length is long,the interfacial shear stress has an elastic-softening-sliding coexistence stage.The shear stress in the elastic,softening and friction sections of the anchorage bonding interface shows different distribution laws,that is,hyperbolic cosine function attenuation,cosine function rise and uniform distribution respectively.The axial force of the rock bolt shows various attenuation distribution laws with the distribution and evolution of the interfacial shear stress.According to the analytical calculation of the anchorage interface model,the ultimate anchorage force approaches a fixed value with the increase of anchorage length when the debonding friction force is not considered.When the debonding friction force is considered,increasing anchorage length can continuously improve the safety factor of anchorage interface.The research results can provide theoretical reference for the analysis of anchoring mechanism and the design of rock bolt support param-eters.
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