Research On Construction Technology Optimization Of Xiamen Shield Tunneling In Rail Transit Engineering

With the development of the economy and urbanization process,the problem of ground traffic congestion in our country is becoming more and more serious.It is urgent to develop underground space and underwater space.With the completion of the undersea tunnels such as the Xiamen-Xiang'an Tunnel and the Qinghuang Island-Jiaozhou Bay Tunnel,the technology of undersea tunnels is gradually developed.At the same time,the development of domestic rail transit is fast,in 2017,the total length of urban rail transit lines in China is 5032 kilometers,the length of the pipeline under construction is 6,246 kilometers,and the planned length is 7321 kilometers.At present,the number of tunnels and underground projects in China is the largest in the world.However,with the development of rail transit project,some problems have gradually emerged,such as diversification of geological conditions,normalization of cross-river crossings,diversification of structural sections,and complicated construction environment.In this paper,through the application of literature research,empirical research and comparative analysis,reviewed the research status of shield tunnel theory and application at home and abroad.We analyzed the development tends of domestic and international shield tunnels,especially undersea tunneling.Secondly,we compared the shield tunneling method/TBM method,the immersed tube method and the mining method.It is.concluded that the shield method is the first choice for the construction of rail transit tunnels and undersea tunnels in China.And then,we analyzed the common risk source in construction process of shield tunneling,the risk source in the special case of high water pressure,and the difficulties in the shield tunneling project of Xiamen Rail Transit Line 2(from Haishu Avenue Station to Dongdu Road Station).We put forward corresponding construction measures for these risk sources,and optimize them to effectively reduce the construction risk of shield tunneling.This is also the innovation of this paper.We conducted an in-depth study on the entire construction process of the first shield tunneling cross-sea tunnel in China,Xiamen Rail Transit Line 2(from HaishuAvenue Station to Dongdu Road Station),and determined that the construction scheme of the project includes the shield method and the mining method.The shield method is the main method,and local stratum construction combined with the mining method.Based on the actual engineering situation,we analyzed the major risk sources of the shield tunneling method,such as special stratum blasting operations,special formation pressure changing into the warehouse for tool change and hot work,crossing special strata,mine section shield construction,etc.Then the construction technology optimization measures were put forward.By comparing the construction effects before and after the optimization of the risk source,the result shows that the optimization measures can effectively reduce the risk of undersea construction,and that can provide reference for similar undersea shield tunnels.