Abstract:

The upgrade project of LianHuo expressway crosses over Wenxiang tunnel on ZhengzhouXi’an highspeed railway. In the paper, 3D simulation analysis is made on the construction process of the expressway upgrade by means of FLAC 3D finite difference program. The safety state of the highspeed railway tunnel is studied in terms of displacement in both crosssection and longitudinal profile. Conclusions drawn are as follows: 1) In the longitudinal profile, the displacement  of the invert is less than that of the crown, the displacement is influenced by both the topography and by the relationship between the tunnel and the expressway upgrade excavation area, the maximum displacement (6.3mm) occurs at the crown at Station 50m, and the maximum differential settlement in every 10m section is 0.97mm, which is smaller than the limit value of the highspeed railway tracks; 2) In the crosssection, due to the unloading effect caused by the overlying expressway upgrade excavation, the tunnel structure has a uplift tendency toward the excavation area; 3) The  upgrade construction practice and the monitoring data show that, due to the layerbylayer excavation in vertical direction and sectionbysection excavation in longitudinal direction adopted, the structural deformation of Wenxiang tunnel  has been brought under effective control, and the construction safety of the expressway upgrade works and the operation safety of the highspeed railway tunnel have been guaranteed. 

Key words: expressway upgrade, highspeed railway tunnel, safety state, FLAC3D