Research On The Transverse Interaction Mechanism Of The Double-Layer Lining Structure For Shield Tunnel

As the underwater shield tunnels with super-long, large cross-section and high hydraulic pressure being common, single-layer segment lining can’t satisfy the safety and durability any more, which results in the increasing demand of double-layer lining. At present, there is a controversy over the role of the shield tunnel secondary lining and a unified structure calculation theory on the double-layer lining used in shield tunnels has not yet formed.This paper conducts research on the basis of Shiziyang Tunnel of Guangzhou-Shenzhen-Hongkong Passenger Dedicated Railway. Theoretical analysis, model test, finite element analysis and other research means are mainly adopted to analyze the transverse mechanical characteristics of the double-layer lining in the large-scale underwater shield tunnel, and to explore the interaction mechanism between segments and secondary lining. It is also used in establishing the three-dimensional discontinuous contact model combined with the model test of double-layer lining. The main results are as follows:1、Taking the composite structure of shield tunnel linings in construction time 0% for example, the double shield tunnel lining segments and the secondary lining structure load distribution model is reserched and the secondary segment mechanical properties of lining structure and internal force distribution ratio between the cross-section linings vary with load step trend is proved based on the different time of the completion of secondary lining, the compound structure and the overlapping structure respectively.2、Model test of double-layer lining structure mechanical characteristics under different water and soil pressure fields is conducted so as to discuss the mechanical characteristics of the double-layer lining in different loading steps in 0% and 100% of the construction time under the compound structure and the overlapping structure respectively and to reveal the interaction mechanism of double-layer lining.3、According to the time effect of mechanical properties of the large underwater shield tunnel segment lining, the mechanical characteristics of the double-layer lining and accumulated damage is analyzed, and also the rational construction time of secondary lining based on the theoretical analysis and the data of model test is obtained.4、Based on the beam-spring model and the shell-spring model for shield tunnel with double-layer lining, the three-dimensional model are established according to the structure forms of contact surface between the primary and the secondary linings. The model adopts plastic-damage model to represent nonlinear characteristic of concrete. Considering the effect on the mechanical behaviors by using rebar built in segment, Esmaeily&Xiao model is adopted to simulate yielding, hardening and softening phenomenon of the reinforcement. In this model, the segments and the segment rings are linked by three-dimensional bolts instead of spring elements. The discontinuity between the assembly block of shield segment and connecting bolts as well as the contact relationship between each assembly block can be truly reflected in this model.