The excavation of large-section loess tunnel with shallow unsymmetrical pressure is easy to cause surface subsidence,which affects the safe use of existing buildings on the surface.Taking Baita Moun-tain tunnel in Lanzhou as the engineering background,this paper simulates the dynamic process of tunnel excavation and support by double-side wall method and middle-partition wall method by ABAQUS finite element software,and also analyzes the deformation and stress characteristics of surrounding rock and sup-port structure and the influence of surface subsidence on ancient buildings.The results show that the verti-cal deformation of the surrounding rock of the deep-buried soil excavated by the two methods is larger than that of the shallow-buried soil,the settlement of the ground surface and the vault is synchronous,and the dangerous construction section is consistent.The maximum ground settlement is 10.7 mm when excavated by double-side pilot tunnel method.The secondary lining stress is mainly distributed in the vault and arch waist,and the most dangerous construction section is the excavation of the middle and upper soil,but the process is complicated and the construction progress is slow.The maximum settlement of surrounding rock caused by middle partition method is 23.0 mm,and the maximum settlement of ground surface is 13.0 mm.The secondary lining stress is mainly distributed in the vault and arch shoulder,and the most dangerous working condition is the excavation of the upper right step.The influences of the two excavation methods on the ancient buildings are in line with the requirements of relevant codes.Considering comprehensively,the middle partition wall method is more suitable for controlling the surrounding rock and surface deforma-tion of the shallow-buried unsymmetrical pressure section.
维普
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