Finite Element Analysis And Experimental Study On Mechanical Properties Of Precast Utility Tunnel Joints

Utility tunnels can integrate various urban pipeline systems in a well-organized way,and is being vigorously promoted by our country in recent years.Prefabricated-assembly technology has become one of the new trends in the development of the construction technology of utility tunnels,because it can make construction period shorter and is more environmentally-friendly.As a kind of prefabricated utility tunnels,sectional prefabricated utility tunnels have more joints so they are more complex.The researches on mechanical properties of the joints of sectional prefabricated utility tunnels at home and abroad are not common.Based on the project of the utility tunnels at Wujiu Line,some mechanical properties of the sectional prefabricated utility tunnel joints are studied by using an experiment and finite element analysis in the thesis.A loading test of the reduced-scale sectional prefabricated utility tunnel model was conducted.Internal force distribution,failure mechanism,the variations of the deflection and the expansion of the joints during the process of increasing concentrated load were studied.Then a theoretical model for calculating the bending stiffness of the joint was proposed according to the scatter plot of bending moment-expansion.A finite element model of the specimen was established and the numerical analysis on its mechanical performance under the concentrated load was done.The numerical results of deflection,expansion and stress were compared with the experimental results to verify the reliability of the finite element analysis model.Four kinds of uniform loads which may occur in actual engineering conditions were respectively applied to the numerical model,and the deflection variation of the joints,the stress of concrete at the critical point,the stress of the reinforcements in the utility tunnel and the bending stiffness of the joints under the different uniform loads were studied.A full-scale finite element model of the sectional prefabricated utility tunnel was established,and the same uniform loads were applied to it.The similarity ratio of the deflection of the joints,the concrete stress at the critical point,the bending stiffness of the joints were studied.Some suggestions were provided on the design of the sectional prefabricated utility tunnels in the project based on the numerical results.