| 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 integrity, and relatively low 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.Aiming at the middle pilot drift method, numerical simulation with FEM has been carried out by applying software ANSYS for tunnel construction based on model of double-arch tunnels in Si-xiao express highway in Yunnan province. Mechanical behavior of unsymmetrically loaded double-arch tunnel construction has been analyzed and studied, mainly research is as follows:(1) Numerical simulations of six projects, aiming at different orders of excavation or combined bolting and shotcrete, have been carried out to analyze the variety of rock stress around tunnel, the development range of plastic zone, the stress state of mid-board, and the stress character of the whole lining structure.(2) Optimized construction project of unsymmetrically loaded double-arch tunnel has been obtained by comparing simulation results of key steps of construction based on different projects.(3) The 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, mid-board and tunnel liner tend toward broking in terms of value of major (minor) principal stress.(4) Applying theory of stress transfer to the explanation of prior construction of deeper tunnel.(5) Influence on stability of rock around tunnel, produced owing to different gradient of slope and depth of tunnel, was analyzed by numerical simulations of two projects. |
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