Shield Segment Deformation Performance Test And Simulation Analysis Under Complicated Working Condition

Nowadays, the universal segment lining with staggered joints is prevalent in the metro construction in China. However, for various causes, a plenty of shield tunnel lining problems have emerged, including structural and durable damage, impeding the normal operations of the metro seriously. In particular, radical deformation, one kind of structural damages, would not only affect the vehicle’s driving indexes but also reduce the overall bearing capacity of the structure of shield segment lining, and consequently threatening the security and reliability of shield tunnel. Therefore, extensive attention from both the operating companies and the society has been drawn on the security and performance of the universal segment. And it has become evident that segment tunnel deformation mechanism and influence factors need further exploration.In addition, given the lags that build cities around metro line usually, later construction is inevitable, which especially deep foundation pit construction adjacent to the tunnel has a severe impact on the security of the shield structure. Shenzhen metro line 1 is one of the earliest universal segment user in the mainland, and due to historical bottom-soil stack and waterline’s drawdown, the segment structure has suffered in serious convergence deformation and damage.In the meantime, a huge foundation pit is constructing onto the destructed shield tunnel. So at present, whether the tunnel could withstand the subsequent construction load remains untested.For the above, the research is conducted from the following aspects:(1) A full-sale full-ring tunnel segment lining test Based on the damage existed in qianli intertval of shenzhen metro line 1, a full-scale full-ring tunnel segment lining test on two hundreds staggered joints among qianli section and another three ones nearby is designed and conducted to analyze the tunnel ultimate bearing capacity, and to verify the security and reliability of the involved shield tunnel under the dangerous condition.(2) A three-dimensional nonlinear contact finite element simulation A three-dimensional nonlinear contact finite element model is established synchronously,which is used to replay the segment test and verify the correction of the model. Then by comparative analysis, the mechanism of segment structure deformation isDeveloped and meanwhile it has been clear that plastic hinge in seam and the friction between segment rings have decisive influence on segment ring’s deformation and damage.What’s more, parametric analysis is conducted on sensitivity of friction coefficient in order to identify loading path of segment structure.(3) analysis of shield tunnel deformation influence factorsThe research further discusses the influence of load fluctuation caused by the bottom overloading, lateral unloading and waterline’s drawdown on shield tunnel structure and the erection method. The result shows that the difference between the top forces and lateral forces has a controlling effect on convergence deformation of the segment ring.