Large Span Multi Arch Tunnel Construction Methods And Reasonable Supporting Parameters Optimization

As an especial tunneling structure,double-arch tunnel has many advantages,such as high flexibility to different landform condition,smooth line shape,less occupation of space,large span,structural integrated cost,At the same,time, Attribute of tunneling structure leads to the complicated mechanism response of rock and structure during construction。Process of double-arch tunnel construction should be studied.In this paper, based on si-chuan lang-zhong jia-ling river four bridge connecting dong-shan multi-arch tunnel engineering, the finite element software ABAQUS to tunnel construction has carried on the finite element numerical analysis, step-by-step excavation process under the action of the bias in multi-arch tunnel, this paper analyses the mechanical behavior of the whole process of construction, the concrete work is as follows:①Numerical simulations of six projects,aiming at different orders of excavation,have been carried out to analyze the variety of rock stress around tunnel,the stress state of mid-board,and the stress character of the whole lining structure.②Optimized construction project of unsymmetrically loaded double-arch tunnel has been obtained by comparing simulation results of key steps of construction based on different projects.③The laws of stress distribution of rock around tunnel and mechanical variety of mid-board, the whole lining structure during construction have been obtained by means of general analyses. Indicate the position in which rock around tunnel, min-board and tunnel liner tend toward broking in terms of value of major(minor) principal stress.④From the point of view of changing the number and length of anchor, calculation analysis of surrounding rock stress distribution, force situation of middle wall, and optimize the multi-arch tunnel supporting parameters.