Study On Mechanics Characteristic Of Support Structure Of Multi-Arch Tunnel

When constructing senior highways in China, the project of multi-arch tunnel is often adopted in special geologic and limited topography districts in order to meet the need of road type and outspreading road, to get better technological and economical purpose. But through the survey and summary of multi-arch tunnels which still being under construction and which have been completed, it shows that the mechanics complexity of support structure and center pillar crack and leakage of multi-arch tunnel are outstanding problems in design, construction and service of multi-arch tunnel. So it is vital that makes study on the choosed center pillar structure type and mechanics characteristic of support structure of multi-arch tunnel in design of multi-arch tunnel.The paper first makes the analysis for surrounding rock pressure distributing and mechanics characteristic and work state of primary lining in the locale monitoring measurement, and through combining with the locale data analysis, simulating the locale construction and calculating by reasonable preferences in the finite element calculation, putting the feasible design reference point about primary lining structure of the different center pillar.Then the paper establishes the load model and the load definition based on the assumption of two slumping arches, combining with the surrounding rock pressure distributing of the locale monitoring measurement, and makes the calculation and analysis for mechanics characteristic of second lining about the different center pillar multi-arch tunnel by using the load-structure model, confirming crack matter between the second lining and integral center pillar,and makes the analysis and opinion for long-term security of second lining structure,combining with mechanics analysis about second lining in the locale monitoring measurement, and puts the second lining design essential of multi-arch tunnel and the second lining design reference point of the different center pillar.Finally, through establishing the plane elastic and plasic FEM, the paper simulate the constructing process of the different center pillar multi-arch tunnel, and make the contrast and analysis for supporting structure mechanics characteristic and the center pillar mechanics behavior, then the center pillarstructure are made the contrast analysis, the result shows that the flexural layer is the optimization,but the stability is more badly in construction,so it is optimized farther again in order to make it used best in the practical project. At the same time, the paper probes into how to confirm the load about the center pillar design and make the control design for the center pillar. Through analyzing data of the monitoring measurement, the paper also discusses the stress changing law of the supporting structure and surrounding rock during the construction of muti-arch tunnel, comparing its result with the result of numerical simulation. So the paper has the guiding significance to the design and construction of the similar tunnel engineering.