The Large Span Arch Tunnel Surrounding Rock And The Mechanical Properties Of The Field Test And Numerical Analysis

As a structure type, muti-arch tunnels are widely used in practice due to their advantages of the smoothly line,small area of project and good connecting between the tunnel and bridge. So the double-direction four lanes muti-arch tunnels are gradually replaced by six lanes tunnels as the traffic in domestic increasing in recent years. Because of the large-span and the complex mechanics of double-direction six lanes tunnels , it is a threat to the construction safety and the structure stabilization. It is necessary to study the mechanical characteristics of surrounding rock and tunnel structure of the large-span muti-arch tunnels during the construction.Based on the actual geological and construction conditions of Wujiazhuang Tunnel, field observations and numerical simulation are adopted to study the interaction between surrounding rock and tunnel structure. The mechanics characteristics of large-span muti-arch tunnel under construction are inverstigated systematically. The main contents are as follows:1. A typical field observation section of K41+896 of Wujiazhuang Multi-arch Tunnel was chosen to monitor the behaviors of surrounding rock and tunnel structure. Based on the analysis of the field data measured during the construction, the thesis gains the following conclusions: the change rules and characteristics of the horizontal convergence and settlement of the surrounding rock ,the tangential and radial stress of the shotcreting, the internal force of the steel arch frame, the internal force of inner middle-wall, the contact pressure between preliminary lining and quadric lining and the internal force of quadric lining during the process of construction. At the same time, the security of the middle wall, the quadric lining and the steel arch frame are evaluated.2. According to the actual construction procedure of Wujiazhuang Tunnel, both FLAC3D and FLAC2D are used to simulate the construction of the tunnel, and the simulation results are according with the field data. Finally, the compare between the results of two-dimensional and three-dimensional simulation shows that the 2D model can replace the 3D model in some conditions.3. On the base of the results of field observations and numberical simulations, some suggestions have been proposed on the design and construction of large-span muti-arch tunnels.