Experimental Study On The Bearing Characteristics Of Suspension Bridge Tunnel Type Anchorage

Tunnel anchorage is one of the important anchorage forms of suspension bridges.Because of the complicated and changeable nature of the surrounding rock of the tunnel,the understanding of the bearing mechanism of the tunnel anchor is not deep enough,and the relevant theoretical system has not yet been formed.The on-site model test is an important method to study the bearing characteristics of the tunnel anchor.This paper is based on the tunnel anchorage of the first railway suspension bridge Lijiang to Shangri-la railway jinsha river.The in-situ model test and numerical simulation of the tunnel anchor are carried out.The main research contents and results are as follows:(1)Based on the similarity theory,considering the design load and size effect of the tunnel anchor,the mechanical response characteristics of the tunnel anchor under actual stress conditions are objectively and truly reflected.The scale ratio of the model test is determined to be 1:10,and the structure size of the model anchor is obtained.(2)The design and implementation were carried out from the application methods of the load,the manufacture of the reaction plate,the placement of the model anchor body,and the placement of the loading and monitoring elements.(3)Through the analysis of the test results,it is obtained that at all levels of dead load and cyclic load,the axial force of the section increases approximately linearly with the increase of the external load;When the load is large,the increase of anchor length has less effect on its bearing capacity.(4)Under load,the axial force of the anchor surface is attenuated from the rear anchorage to the front,and the attenuation rate is slowed down in turn.The anchor body near the back of the anchor is more effective than the anchor in the former anchor chamber,and the closer the anchor chamber is,the higher the proportion of the anchor is.The anchor bearing potential of the stay away from the back anchor.is not fully mobilized and still has a large wealth.(5)The FLAC3 D finite difference software was used to numerically calculate the anchorage of the Shangri-La Shore Model Anchor.The deformation,stress,and distribution characteristics of the plastic zone under the design load and overload conditions were analyzed.The calculated results were basically consistent with the measured data of the in-situ model test.The development of the plastic zone and the load-displacement curve show that the ultimate bearing capacity of the model anchor is(13~14)P.The existing design of the engineering tunnel anchor can meet the bearing capacity and displacement requirements.