Abstract: To solve the concrete pouring difficulties in the construction of a composite lining under high internal pressure, such as the void forming in the vault and low pouring compactness in dense areas, this study conducts full-scale model tests for application of three different mix proportions of prestressed concrete in a double-layered steel strands lining structure. Concrete pouring quality is controlled by a device suitable for monitoring the voids in the vault, and pouring effects of different mix proportions are compared and analyzed. The results show that (1) better pouring effect is obtained by changing the aggregate of ordinary concrete from two-graded to one-graded and adopting a reasonable vibrating technology. (2) Self-compacting concrete can reduce the voids in the vault and improve pouring quality, but it needs to control material shrinkage and creep deformation and take certain temperature control measures. (3) The temperature of concrete flattens out in 8 - 10 days. This study recommends that in the case of the steel strands under tension, the curing should not be less than 14 days.

Key words: shield tunnel, double-layered steel strands, full-scale model test, prestressed concrete, void monitoring