Experimental Research On Mechanical Characteristics And Ultimate Bearing Capacity Of Tunnel Anchor Of Suspension Bridge

As one of the important anchoring forms of suspension bridge,tunnel anchor is a complex system composed of anchor plug and surrounding rock mass.Because the force and deformation of the tunnel anchor involve the interaction between the anchor body and the surrounding rock mass and the deformation and failure of the rock mass,the deformation and mechanical characteristics of the anchor body and surrounding rock are very complex.At present,there is no complete and reliable experience to be used for reference.Among the many research methods,model test is one of the most intuitive and credible research methods.In this paper,based on the tunnel Anchorage of Jinsha River Bridge,the mechanical characteristics,ultimate bearing capacity and failure form of tunnel anchor are studied by insitu model test and indoor model test.The main research contents and achievements of this paper are as follows:(1)The geometric similarity ratio of the in-situ model test is determined to be 1 to 10,and the structural size of the model tunnel anchor is obtained from the geometric similarity ratio according to the similarity theory.The location of the model anchor hole,the method of applying the load,the installation of the test elements in the anchor body,the monitoring of displacement and strain are designed and implemented.(2)Considering the influence range of tunnel anchor loading,the geometric similarity ratio of indoor model test is 1 to 100,and the size of indoor model test model box is 2m × 1m × 1m.According to the similarity theory,the structural size of the model anchor and the similarity between the surrounding rock and the anchor body are obtained.The strength index value of the material.The model box making of indoor model test,the method of applying load,the arrangement of loading and testing original parts,and the filling of similar materials between anchor body and surrounding rock are designed and implemented.(4)Based on the analysis of the indoor test results,it is found that the maximum displacement of the tunnel anchor occurs on the anchor surface behind the anchor body,and the surrounding rock and surface displacement are small.It is concluded that the failure mode of the tunnel anchor is the shear slip failure of the interface between the anchor body and the surrounding rock.Through the loading tests of the anchor body with different parameters,it is found that the bearing capacity of the tunnel anchor will be increased by increasing the length and slope ratio of the anchor body.(5)Based on the analysis of the results of in-situ model test of Lijiang bank,it can be found that under the action of all levels of rheological load and cyclic load,the displacement of anchor body and surrounding rock is small,and the rheology is attenuated,and the limit state of bearing capacity is not reached when it is loaded to 12 p.It shows that the anchor design of Lijiang bank tunnel can meet the requirements of bearing capacity and displacement.(6)From the field in-situ model test and indoor model test,it can be concluded that the anchor load of the tunnel is transmitted from the back anchor surface of the anchor plug to the forward anchor surface,and the axial force of each section increases linearly with the increase of the load.The closer to the anchor surface behind the anchor plug,the greater the proportion that plays a role,In the field in-situ test,when the load is unloaded to 00:00,the axial force of the anchor plug can basically return to zero,and the anchor plug body is in the elastic stage.