Study On The Mechanical Characteristics Of Highway Tunnel Lining Structure Reinforced By Overlapping Sprayed Concrete Arch

Most of the early tunnels built in my country have cracks,water leakage and other diseases,which need to be reinforced and repaired in time.Overlapping arch reinforcement is a common reinforcement technique for adding an arched concrete structure along the surface of the original lining and combining it with the original lining to form a common bearing body.However,the current design and calculation of Overlapping arch reinforcement schemes mostly use the empirical analogy method,Has not yet formed a unified and reliable calculation method and theory.Therefore,it is very important to carry out the research on the mechanical characteristics of superimposed arches.Based on the Baliguan tunnel disease treatment project as the background,this paper comprehensively uses numerical simulation,field testing and other research methods to conduct an analysis of the mechanical characteristics of the superimposed shotcrete sleeve arch reinforced highway tunnel lining structure.The main research contents and conclusions are as follows:(1)The disease situation of the Baliguan tunnel was sorted and counted,and the superimposed shotcrete arch was used to reinforce the disease,and its construction process and on-site test plan were introduced in detail.The changes and distribution of the contact pressure between the original lining and the arch,the stress of the grille arch and the internal force of the arch are studied by field tests.(2)On the basis of load structure method,the model of overlapped arch structure is established by Midas GTS NX software.The model is used to simulate the disease treatment project of Baliguan tunnel.According to the influence of cracks on the strength of lining,the actual material parameters of lining after strength reduction are determined.By comparing the forces on the original lining of the tunnel before and after reinforcement,it is concluded that the shotcrete arch has an obvious reinforcement effect on the original lining.(3)The established model is used to study the influence of different structural parameters on the stress state and deformation of the structure,and the change law of the contact pressure between the original lining and the arch under different degrees of lining degradation is obtained,which can provide a reference for the design load value of the shotcrete arch.When the strength of the original lining is reduced to less than 70%,the load-bearing capacity of the lining will decrease faster and faster.Therefore,it is necessary to check regularly and take reasonable reinforcement measures in time.Increasing the strength of shotcrete does not significantly enhance the effect of shotcrete arch reinforcement.The stiffness and bearing capacity of composite structure can be increased by increasing the thickness of spray layer.Therefore,the thickness of the spray layer can be appropriately increased while meeting the requirements of building boundaries.