Study On Bearing Capacity And Optimization Design Of Secondary Linings In Highway Tunnel

Currently, many tunnels are designed and constructed by the New Austrian Tunneling Method. Composite lining is corresponding with this method and make up of primary support, waterproof layer and secondary lining. And the secondary lining is required strictly to construct after the deformation of surrounding rock and primary support was basic stability. To the design of primary support, the civil engineering industry has reached an identical attitude now. In other words, we have the almost same design of primary support on the same excavation of the section or the same geological conditions. However, the thickness or the need for reinforcement of view to the secondary lining is very different. But it is directly related to the excavation of the size and project cost. By means of numerical simulation and in-situ test, this article research on distribution rule of surrounding rock pressure and contact pressure and safety evaluation and design optimization of secondary linings. The main conclusions and results are as follows:1,Based on stress tested in-situ, analyzed on surrounding rock pressure and contact pressure ofâ…¤-class surrounding rock,â…£-class surrounding rock,â…¢-class surrounding rock in deep-buried andâ…¤-class surrounding rock in shallow with statistics method to have the distribution of the general laws and the shared ratio of surrounding rock pressure of secondary lining;2,Compared surrounding rock pressure tested in-situ with classical theory results ofâ…¤-class surrounding rock, IV-class surrounding rock andâ…¢-class surrounding rock in deep-buried, the result from the Pu's theory, Terzaghi theory, deep-buried surrounding rock pressure formula of highway tunnel design specification is closest to the measure value respectively;3,With the method of the finite element numerical simulations, research on different side-pressure coefficients and thickness of secondary lining to the influence of the deformation and internal force of tunnel, evaluate the security and find the optimization thickness of it;4,Take the project cost as objective function, use the internal penalty function method to establish mathematical models with strength of structure conditions and reinforcement rate as constraints, optimize analysis on the secondary lining thickness and reinforcement.