Study On Segment Design And Stress Of Metro Tunnel Under Mining Method And Shield

A shield to pass through the tunnel section excavated by drill and blast(D&B)is a combined construction method appears late,it has the advantages of short construction period,low risk and high economic benefit.The lining segment is the permanent support structure of the tunnel,in order to ensure the long-term stability of the tunnel,its internal force distribution and stress characteristics should be paid more attention to.Here we takes the construction tunnel of the Han River section of Wuhan Metro Line 3as the background,design the shield segment in the combined construction method,and calculate the internal force of the segment.The main research work is as follows:(1)The type of segment and its combination form are systematically analyzed.According to the actual situation of the project,their advantages and disadvantages are compared.The suitable range is given according to the analysis results.On the basis of the specifications and practical engineering,the structural parameters of the segment such as the diameter,thickness,width and the vertical structural forms are determined.It provides the reference and analytical analysis for segment design in similar projects.(2)By comparing the applicable conditions of different segment calculation methods,using modified routine method to calculate segment internal force of shield tunneling method,and the internal force and distribute regulation of the segment are obtained(3)Based on the finite element method,a two-dimensional model of initial lining and shield tunnel lining is established to analyze the stress condition of the segment during the solidification stage.By comparing with the shield method,the bending moment of the segment under the combined method is about 1/10 of the shield segment and the axial force is about 2/3.If the combined method directly employs the segment design of shield method,it will not make full use of the segment's performance,resulting in waste of materials.(4)In order to optimize the segment design,the formation parameters and structure parameters are studied.Quantitative analysis of the relationship between the parametersand the internal force change of the segment have been made.Through polynomial fitting,the function relation is obtained,which provides theoretical reference and basis for the future optimization design.