Full-scale experiment on the bearing and deformation characteristics for prestressed double-layered shield tunnel linings under high internal pressure

To investigate the bearing mechanism for two types of circular anchorage prestressed double -layered shield tunnel lining under high internal pressure, a set of loading systems and measuring schemes were dedicatedly designed for the standing full-scale lining model. The results show that when the internal pressure reaches 1.10 MPa, the proportion of internal pressure transferred to the outer lining begins to increase with the expansion of the inner lining. When the internal pressure reaches 1.30 MPa, the local cracking of the inner lining will cause structural stiffness variation and stress redistribution, leading to a further increase in the proportion of internal pressure transferred to the outer lining. In addition, the detached bearing structure makes better use of prestress and has a higher bearing capacity, but lower engineering material economy than the combined bearing structure. For the combined bearing structure, there is an initial gap between the inner and outer lining at the left and right arch due to the prestress tensioning and concrete shrinkage. Moreover, it can give full play to the bearing performance of the segment and surrounding rock, thus optimizing the diameter of the prestressed steel strands. However, the initial gap has a certain influence on load -transferring, and it is necessary to control the concrete shrinkage and adopt the backfill grouting.