| Changsha Hongqi Canal was built in the 1950s.It is located in the urban area east of the river in Changsha.The water system is the combined system of rain and sewage.The main canal of the red flag canal has been used for a long time and lacks routine maintenance.There are many historical debts,and the pipe canal materials are aging,resulting in deformation,uneven settlement,collapse and other diseases of the pipe canal.Therefore,it is extremely urgent to repair and strengthen the existing pipe canal structure.Because the buildings above the main canal of Hongqi Canal are dense and belong to the urban transportation hub,it is difficult to use the traditional excavation and repair method,so it is decided to adopt the non excavation repair method to strengthen the structure of the canal.A section of the main canal of the red flag canal is selected as the test section to study the feasibility of four construction methods,such as formwork method,jet method,spiral winding method and prefabrication method,in the structural reinforcement project of the red flag canal.In this paper,the feasibility of trenchless repair technology by precast method and the determination method of key parameters of reinforcement design by precast method are studied.Through the bending test of UHPC precast segment and ordinary concrete precast segment,the feasibility and advantages of strengthening urban underground drainage arch culvert by precast method using UHPC precast segment are studied;In the whole structure reinforcement design of underground drainage arch culvert,in order to simplify the calculation,the original arch culvert structure and surrounding soil can be equivalent to the boundary condition of reaction spring.Therefore,the equivalent reaction spring stiffness of the original arch culvert structure and surrounding soil is the key parameter in the reinforcement design of precast method.Therefore,the determination method of equivalent reaction spring stiffness of masonry arch culvert is studied.The specific work is as follows:(1)Through the bending test of UHPC cast-in-situ precast segment and ordinary concrete cast-in-situ precast segment,the feasibility and advantages of UHPC precast segment in the reinforcement of underground drainage arch culvert are studied;Through the bending test of grouting sleeve splicing members,straight bolt splicing members and curved bolt splicing members,the mechanical characteristics and working performance of prefabricated segments under bending moment load are studied.(2)The equivalent reaction spring coefficient of the mortar rubble side wall and brick arch ring of the original masonry arch culvert is calculated by the finite element method,and the original arch culvert and surrounding soil outside the arch culvert structure newly strengthened by the prefabrication method of the red flag canal test section are equivalent to the equivalent reaction spring boundary conditions calculated by the finite element method for the whole structure reinforcement calculation,and the calculation results are compared with the field monitoring data,Verify the reliability of the equivalent reaction spring stiffness of masonry arch culvert calculated by finite element method.At the same time,the effects of material strength of masonry arch culvert,bearing capacity and Poisson’s ratio of foundation soil layer,moisture content and Poisson’s ratio of outer soil layer and moisture content and Poisson’s ratio of plain fill layer on the equivalent reaction spring stiffness of masonry arch culvert are studied,and the recommended formulas for calculating the equivalent reaction spring coefficient of mortar rubble side wall and brick arch ring are obtained.(3)Through the finite element simulation,the influence of the side wall equivalent reaction spring coefficient,the arch ring equivalent reaction spring coefficient and the foundation soil equivalent reaction spring coefficient on the internal force of the arch culvert structure newly strengthened by the prefabrication method is studied. |
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