Effect Analysis on Tunnel Serviceability State by the above Expressway Extension in Loess Area

Based on the typical adjacent project of extension of LianHuo expressway which is constructed on WenXiang tunnel, the finite difference software, Flac3D, is adopted to stimulate the process of the construction. In this paper, from two aspects, the deformation of profile and cross-section, serviceability state is analyzed in detail. In the profile plot, usually displacement of the invert arch is less than that of the vault, and affected by the mutual position of topography and excavation, the maximum displacement, 6.3mm, merges at 50m of the vault in the profile plot; in the cross-section plot, due to occurrence of unloading effect brought by overlying excavation, tunnel structure has the tendency of rising toward the excavation. The calculated result shows that the displacement of WenXiang tunnel locating on the line of ZhengZhou-Xi’an Railway High-speed can be well controlled by adopting the excavation method of layering excavation at vertical direction and section excavation at longitudinal direction, which makes the safety of serviceability state of extension of expressway and the operation of Railway High-speed.