A Study On The Characteristics Of Excavation In Upper Part Shield Tunnel And Security Protection Technology Research

With the modernization of Chinese urbanization process, the gradual expansion of urban space focus on the underground space, and thus gave birth to a large number of underground engineering. Structures of underground space have been built to meet the increasing demand for people's life and work, at the same time, the follow-up projects have to face inevitable technical difficulties. Problems came out that how to ensure the stability and security of built underground structures, one of which was the unload of the underground structures at the top.In this paper, base on Shanghai Subway Line No.10, Tongji station to GuoQuan road section, underground interchange project. We research on the upper unloading of the shield tunnel, meanwhile, analysis and compare methods of excavation unloading the construction process, reinforcements of the interchange project and other factors, Then we find out how these factors affect on the shield tunnel under-lying, analysis on sensitivity and response, and conduct portfolio analysis. Based on the comparison of different factors, we find some propose appropriate countermeasures to solve engineering challenges, and environmental protection measures to ensure the safety of rapid construction. The main research contents are as follows:(1) Describe the relevant theory and finite element numerical simulation of tunnel construction methods, using non-linear Drucker-Prager soil model, the approximate assumptions used in analog processing, the selection of soil parameters and conversion, and the implement of construction steps.(2) Through the three-dimensional finite element model, analysis the floating volume of built tunnel under different ways excavation. By assess the excavation process in space-time effect on the basement uplift control, choose the best method of qualitative excavation.(3) Establish a two-dimensional finite element model, then simulate the six selected strengthening program, study the tunnel floating control effect, through out the comparison of displacement by different reinforcement methods, consider the actual construction and engineering economic factors, then select the best integrated reinforcement.(4) Analysis the measured data, under the excavation with appropriate protection program, the surface subsidence of construction process, foundation pit vertical displacement, and building vertical displacement, pipeline displacement are all controlled within reasonable limits.