Abstract:

Pingyuanlu tunnel in Xinxiang is a fourlane shallowcovered tunnel running underneath along existing underground commercial street for 610.55 m. The clearance between the tunnel and the floor slab of the existing structure ranges from 2.0 m to 4.5 m. Three proposals, i.e., separate twin tube tunnel, doublearched tunnel and doublespan rectangular tunnel, are proposed for the project. The influence of the tunneling on the existing structure is analyzed by means of numerical simulations and it is determined that the proposal of doublespan rectangular tunnel should be adopted. The doublespan rectangular tunnel is to be constructed by CRD method and the proposal is optimized in the following aspects: the doublespan rectangular tunnel clings to the existing structure so as to make full use of the existing structure; advance grouting in appropriate range shall be made during tunneling; the design parameters should not be too high, otherwise they cannot be realized during tunneling, and they are not so efficient in controlling the deformation. The study result can provide reference for the design of other similar works in the future. 

Key words: shallow cover, large span, tunnel, existing building, underneath crossing, settlement control