Study On Mechanical Characteristics And Structure Selection Of UHPC Joint For Tunnel Fabricated Lining

The prefabricated lining has the advantages of fast construction speed and avoiding lining damage caused by construction factors.With the maturity of controlled blasting technology,the prefabricated lining will have broad application prospects in railway tunnel.At the same time,given the ultra-high performance concrete(UHPC)with high mechanical properties,the innovative use of UHPC in the assembled lining joint to improve the work performance of fabricated structure,enhance the toughness of the tunnel support system,in response to the sichuan-tibet railway and similar challenges of complex geological environment is a novel feasible design train of thought.At present,the prefabricated lining joints based on UHPC have not been studied,and their working performance is not well understood,and there is no design basis in engineering application.Based on the research of ordinary concrete joints,the full scale load test of UHPC joints is carried out in this paper,and the three-dimensional finite element model is established.The mechanical properties of the joints are studied by the full-scale test and simulation methods,so as to provide the basis for the design and selection of the joints.The main research contents of this paper are as follows:1.Two joint types of flat joint and tenon groove joint were designed,and each joint type was divided into four joint types of non-bolt joint,curved bolt,straight bolt and inclined bolt.On this basis,eight types of ultra-high performance concrete joint specimens were made to carry out joint load test and failure test.2.The measured test data were sorted out and analyzed,and the complex relationship between joint opening,int rotation,joint bending stiffness coaxial force level and bending moment was studied.The deformation characteristics of ultra-high performance concrete joints in the loading process were summarized,and the advantages of ultra-high performance concrete joints were expounded compared with ordinary concrete joints.The variation law of bending stiffness with external load and its internal mechanism are mastered.According to the moment interval,the fitting formulas for calculating the bending stiffness of joints with different types and different connection modes under different axial force levels are given.The bending stiffness difference between flat joint and tenon groove joint was compared and some suggestions for joint selection were given.The load test shows that the ultra-high performance concrete joint has high bending stiffness,strong load-bearing capacity,deformation adaptability and stability recovery ability,which is one of the feasible ideas for constructing the toughness tunnel support system.3.According to the joint load test,a three-dimensional fine finite element model was established by using ANSYS software to study the variation characteristics of joint rotation Angle and flexural stiffness with bending moment for joints with different connection modes under different axial forces,and the flexural stiffness results of numerical simulation were compared with the joint load test results.The results show that,Although the numerical model results are different,they are consistent in law,which can provide supplement and reference for load test.