Large Span Bifurcation Type Highway Tunnel With Already Existing Rail Tunnel Approaching Construction Influence Research

With the raiding development of our various types of infrastructure construction, there has been a great deal of tunnel engineering. In order to better suit the terrain factors and economic factors and many other factors, more complex construction method and bigger difficulty construction tunnel forms. Because of the terrain factors, tunnel group don’t design and construction in the form. The distance between the upper and lower tracks or left and right tracks is changing, and it is high to the surrounding rock and supporting structure, and those bring certain difficulty to the construction. Therefore, in the new environment of the new requirements, to suit one’s measures to local conditions, proceed from reality, to realize the safety and economy is double win. In this paper, relying on the Chongqing Daleizui tunnel engineering, with three-dimensional numerical simulation analysis method, on the basis of the already existing lower rail tunnels, study excavation of the upper highway tunnel the reasonable construction scheme, the new tunnel mechanical changes, and the safety of already existing tunnel in excavation process. The main research work and achievements are as follows:1. According to the terrain environment and tunnel design requirements, the large span bifurcation tunnel achieves with anterior double arch tunnel, middle small spacing tunnel, and posterior segment separated tunnel.2. Select and comparison in the most reasonable two schemes, cross diaphragm method (CRD method) construction lines clear, disturbance of the surrounding rock in small. The interaction effect with supporting structure and surrounding rock can be very good to achieve the simple construction process and construction safety.3. Use finite element numerical simulation respectively double arch tunnel and small spacing tunnel, with different buried depth, deferent tunnel close spaced between up and down and the middle wall thickness or the middle rock pillar thickness as reference factor, the three together to the surrounding rock and supporting structure of role, and only by gravity, buried depth of greater.4. Use three-dimensional transient numerical simulation respectively of double arch tunnel and small spacing tunnel, with the already existing tunnel, the secondary lining change constantly following the excavation of highway tunnel, and the new location of new tunnel effect settlement and stress.