Research On Deformation Failure Mode Of Tunnel Anchorageadjacent Rock Of Long-span Railway Suspension Bridge

Because of its simple structure,clear force,low unit cost and strong span capacity,suspension bridge has great development potential.As a form of anchorage,tunnelanchorage has the advantages of little impact on the environment and relatively low cost.However,because of the small stiffness of suspension bridge,it is easy to produce large deflection and vibration under load,so it has not been used in railway construction at home,and tunnel anchorage requires high engineering geological conditions and the pullout resistance mechanism is not clear,so to some extent the application of tunnel anchorage is limited.Based on the first railway suspension bridge in China,Jinsha River Bridge in Lixiang railway,based on the actual topography and physical and mechanical characteristics of adjacent rock,the three-dimensional finite difference numerical model of the adjacent rock system of the Lijiang bank tunnel of Jinsha River Bridge was established.Referring to the design data of Jinsha River Bridge,the finite element numerical model of Jinsha River Bridge was established.The stress and deformation law of tunnel anchorage adjacent rock under train vibration load and the deformation failure mode of tunnel anchorage adjacent rock under static load are studied.The main research conclusions are as follows:(1)Under gravitational force,the integer displacement direction of the tunnel anchorage adjacent rock system is vertical downward,and increases with the elevation,and there are local tensile failure on the surface of entrance slope and the pile cap of the adjacent rock,and the shear failure of the interface between the anchorage and the adjacent rock on the upper side of the anchorage,and the stability is good;(2)Under the train vibration load,the integer displacement of the tunnel anchorageadjacent rock system is diffused unevenly around the anchorage with the axle wire of the anchorage as the center and gradually decreases,the adjacent rock remains stable,but the tensile failure range at the surface of the entrance slope and the pile cap is enlarged.When the shear failure surface of rock in the upper part of the anchorage is through,the supporting work should be done in time to prevent its deformation and failure under cyclic train vibration load;(3)On the basis of design tensile load,with step by step loading on the anchorage of the Lijiang bank of Jinsha River Bridge,the maximum displacement appears on the interface between anchorage and adjacent rock,and the displacement diffuses uniformly around the anchorage with the axle wire of the anchorage as the center,and decreases gradually.When loaded seven times of the designed tensile load,the shear plastic strain zone of rock on the upper side of the anchorage,on the left and right sides of the anchorage and at the back of the anchorage will increase greatly,and the shear plastic deformation of a large number of rock will occur in the deep part of the anchorage,almost forming through failure surface and the adjacent rock is in the critical state of instability;when loaded eight times of the designed tensile load,the adjacent rock forms an arc through shear failure surface from the left side of the anchorage to the right side of the anchorage,and leads to shear failure of a large number of rock in the deep part,resulting in the overall instability of the adjacent rock;(4)The ultimate pullout resistance of anchorage of Lijiang bank of Jinsha River Bridge is 7-8 times of the designed tensile load,the safety factor is more than 5,which meets the design requirements and has sufficient safety reserve.