| The Underground Railroad of the mass rapid public transport system is an important way to solve the problem of urban passenger transport. The cross segment building projects of Guangzhou metro line5and line6is located in the intersection of Huan Shi Dong Road, YueXiu District and NongLinXiaLu. The4th shaft is set at the southern end of the main tunnel in OuZhuang station of line6. Those are located in the downtown area, building density, concentration of passenger flow, busy traffic, and PingAn building, GuangZhou city highway bureau and other high-rise and low-rise buildings around. Traditional cut-and-cover construction method is simple, but the site requirements high, bring nearby residents a lot of inconvenience, also affecting the normal ground transportation. This paper discuss how to resolve the problem in construction of building proximity subway large span tunnel and multiple closely spaced tunnels on small construction site in the city center basing on specific examples of projects.Proximity tunnel, because of its special spatial relationship and porous particularity in the tunnel construction, affecting factors are more than single tunnel, which can cause the stress state of surrounding rock re-distribution and re-distribution again that leading to a series of mechanical behavior change. Although the actual situation is complex and varied, the mechanism exists the same or similar. On proximity tunnel construction mechanics, conformal mapping tools of complex variables functions and Schwarz alternating method are used to solve the problem at two holes in the plane. Given analytical solution to more complex problems is very difficult. Now it is mainly through numerical analysis, model testing, field testing and statistical analysis, using direct and indirect ways (back-analysis) to determine.Cross tunnel is one of the proximity tunnels, its loading, unloading effect, horizontal, vertical and spatial effects vary as the spatial location, excavation time and excavation method. Mastering the complex construction dynamic characteristics is very important to the construction of tunnel and even underground structural engineering. Today proximity engineering is bound by different factors, its available pitch getting smaller and smaller, and its supporting theory is not mature enough. So, research on the change of structure mechanical principle of cross tunnel construction process is significant.Small shaft turn to large span tunnel construction has the characteristic of complex conversion construction process due to the cross-section drastic changes in a small distance. Ground stress of tunnel intersection is in unstable change for the interaction effect of the construction of the up and down load causing disturbance. In this paper, the stability of space intersecting structure formed by Guangzhou metro line5and line6is qualitative analyzed with three-dimensional modeling via ABAQUS by analyzing the stability of surrounding rock in construction process, the internal force and deformation of the lining of the new and the original structure to determine a reasonable construction technology program. Those can ensure the smooth construction of tunnel cross space structures, make the tunnel structure supporting force reasonable, provide reliable basis for optimization design. Then, it study the cross site mechanical properties on the construction of4th shaft of Guangzhou City metro line6to the southern large-span tunnel, the influence scope and degree to ground nearby causing by the construction of shaft. This thesis analyses the global stability and security of constructing small shaft to large-span tunnel at last. |
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