In course of the approaching excavation of underground works

the construction of new structure will change the mechanics case of existing structure and brings some bad influence. At the same time

the mechanical mode of newly-built structure is not the same as that single cavern is excavated in the half-unbounded space. Its original stress field is disturbed by former time and time again

and once more by excavating of later. A project is taken into account in this paper. By the three-dimensional elastoplastic finite element analysis

results show whether we should reinforce the old tunnel or not

it gives the suggestion

as well as whether the shield driving influences the orbit pitch of the old tunnel. It also simulates three pressure on the shield machine and how to influence the distortion and the principal stress. Finally

it makes the conclusion that may instruct the design and the construction of the project.