Study On Limitation Of Tunnel Deeply Buried And Shallowly Buried In Large Cross-section With Mudstone And Sandstone

In recent years, with the rapid take-off in economy of our country, the growing urban development and the contradiction of urban traffic congestion are becoming ever more obvious. In terms of urban development, just relying on the previous "silver road and gold bridge " is unable to solve the problem of urban traffic congestion, the development of ground transportation has been severely restricted by urban land resource which is so scarce, in order to solve the problem, it only depends on the deep development of urban underground space resources, namely, trying to develop the more urban subways and the tunnels. As is known to all, the tunnel belong to the category of underground structure, and how to distinguish the type of tunnel buried depth in tunnel safety and economy will play an important role. Both road tunnel and railway tunnel, when it passes through the mountain or underground,their structure will be pressed by the surrounding rock mass, and what a buried depth is suitable for this kind of geological tunnel? Also it is important for the building and running of tunnel to select the supporting form. Therefore, according to the actual geological category,how to accurately determine the tunnel is in deeply buried or shallowly buried is particularly important, rather than relying on strong fuzzy empirical data to determine. This article will take the monkey rock tunnel in KaiXian of ChongQing as the engineering example, according to the engineering survey, engineering design data and related specifications, and combined with the finite element analysis software ANSYS to the tunnel buried depth limitation the essay provides a reference for similar projects in the future.By consulting and analyzing relevant data and documents, and through ANSYS finite element simulation, we will get the following conclusion:①Proposed a way which through the analysis of surface subsidence rule of tunnel after excavation as discriminant method of tunnel buried depth limit-the surface subsidence variation method. The results show that there are many differences between the depth of buried depth and the specification limitations, therefore, on the current situation, it is not proper to think this method as the discriminant way of tunnel buried depth.②Put forward a method of tunnel buried depth defined- surrounding rock stress changing method, namely,through the analysis of the tunnel vault nodes vertical stress changing rule before the excavation of tunnel and analysis of the tunnel vault nodes vertical stress changing rule after the excavation to get the limit depth. At the same time,the results seem very like to the standard recommended limit.③Through finite element simulation will get two lane highway tunnel which whole section mudstone formation and sandstone formation buried depth limit depth respectively are 19 m and 30 m. Considering the actual engineering geological conditions are a small amount of sandstone and a lot amount of mudstone, and taking the whole section mudstone and sandstone into consideration, from a security perspective the comprehensive geology buried depth limit is 19 meters to 30 meters.④In view of the project situation is more complex, in the actual project when determine the buried depth limitation, the designer should think about the actual situation of engineering.