A Study On Optimization Technology Of Section And Clear Distance For Large Span Adjacent Tunnels

In this paper, combined with the fifth domestic two-hole and eight-lane highway tunnel, called XinWu tunnel for Shenzhen-Nanping Expressway (Phase II), It’s used with a combination of the oretical calculations, model tests, numerical simulation and other research tools, including large-span and the small-distance road tunnel section optimization analysis, large-span tunnels with small spacing interaction studies, large-span tunnels with small spacing numerical analysis. Using comparative analysis of the theoretical solution and numerical solution and comparative analysis of the model tests and numerical solution, it makes more study in-depth of the tunnel cross-section and spacing optimization techniques. This paper research results include:(1) Large-span and small spacing highway tunnels section optimization analysisSpacing optimization of the tunnels:spacing optimization includes a single stress state analysis of circular tunnel, large section tunnel design parameters and its application in engineering;The tunnel shape optimization: tunnel shape optimization studies including the tunnel optimal shape analysis, shape optimization numerical simulation of large-section tunnel and height-width ratio effects;In the design, compared with the tunnel construction, it has used a tunnel height of13.3m,(the height and width ratio is0.6333), to meet the minimum height requirements, the design is reasonable.(2) Large-span and small spacing interaction analysisThe results of two parallel tunnels can be seen as the second excavation of a tunnel on the basis of the first tunnel excavation and the stress redistribution will occur twice. As the spacing increases, the first excavation of the tunnel has less and less effect on the next excavation of the tunnel. The effects of spacing1.0B,2.0B and3.0B are25%,11%and6%;Model tests for large-span and small spacing tunnel:in order to the purpose of this experiment, it has been achieved by changing the distance between two tunnels to achieve two different proximity tunnel simulation conditions. Analysis has been made on the liner failure mechanism, the main stress, and internal force of secondary lining and plastic zone.(3) The numerical simulation for large-span and small-distance tunnelBy FLAC3D software for optimization and spacing analysis, the following main conclusions obtained: The tunnel axis force sizes of the measuring points are following by wall, arch, arch shoulder and invert, and finally the vault. Arch foot and wall receive a larger moment value, followed by the arch shoulder. Vault has the largest displacement, followed by the spandrel, invert and side walls. As the spacing increases, the arch top with the sinking of the tunnel spacing decreases, the level of convergence with little change in spacing, and plastic zones remained unchanged after spacing of19m.