Research On Mechanical Behaviors Of Foguan Intercity Railway Shiziyang Shield Tunnel During Construction Period

China is in the peak period of constructing underwater shield tunnels recent years with a trend of large cross-section,large cover depth,high water pressure and complex geological conditions.When a shield tunnel passes through rocks,the segment cracking always emerges in large numbers and the theory of segment structure design and load calculation for rock ground still need to be promoted.In view of this,researches are carried out in this paper by means of field test and numerical simulation based on Foguan Shiziyang intercity railway tunnel project to figure out the segmental mechanical behaviors while large diameter underwater shield tunnel passes through meso-weathered argillaceous sandstone strata.The main work and research results are shown as follows:(1)Filed test results of large cross-section shield tunnel which passes through subaqueous meso-weathered argillaceous sandstone strata were analyzed,then the distribution of water pressure,rock pressure as well as axial force and bending moment of segmental lining are presented with time-history curves in different construction stage.It's figured out that the segmental structure produce large internal forces while assembling and local tension would commonly exist in initial assembling.(2)Numerical simulations were counducted for segements assembling and long-term fluidsolid couping tunneling via finite difference method(FDM)and the calculation results were compared and verified with the measured values.It is revealed that the most unfavorable load of shield tunnel construction in full-face weathered argillaceous sandstone is the assembly loads.Then the parameters sensitivity analysis was conducted furtherly and the influence on segmental linings of different construction parameters such as jack force,segment contact paramerts,assembly point and sequence were figured out.(3)Inversion analysis of water pressure and rock pressure as well as surrounding rock parameters was conducted by means of GA-Inversion method when large diameter underwater shield tunnels through meso-weathered argillaceous sandstone strata.Furthermore,the calculation method of corresponding load was proposed.(4)To solve the existing problem reflected by filed test and numerical simulation,relevant suggestions were proposed for shield assembling stage and long-term construction stage based on the results above.For shield tunneling through meso-weathered rock strata,it is reasonable to pay more attention to assembling stage rather than other construction stages.