Immersed Tunnel Fire Test: Reduced-Scale Model & Construction Details

The standard element length of an immersed tunnel is 180 m, which consists of 8 segments, each with a length of 22.5m. These segments are connected through waterproof joints to form an element. Due to the section width of the immersed tunnel being 37.95m and the height being 11.4m, it is difficult to carry out full-scale fire tests. Therefore, a reduced-scale model of the standard segment was built, referring to the reduced-scale tests of the immersed tunnel's shear keys (CCCC Ltd, 2019; Hu et al., 2018). The scale factor was 1:5 due to the limitations of the test site, loading equipment, and heating system. The prototype and reduced-scale model of the immersed tunnel are shown in Fig. 1. The dimensions of the reduced-scale model were 5.8m in length, 7.59m in width, and 2.28m in height. The thickness of the ceiling, arch wall, side wall, and floor were 300mm, while the thickness of the mid wall was 160mm. The structure and rebar form of the immersed tunnel are shown in Fig. 2. The same materials (C50 concrete and HRB400 rebar) were used to build the immersed tunnel. Table 1 contains the information of the C50 concrete mix. The coarse aggregates used in the concrete were broken gravel (siliceous aggregate), and the sand was mix sand.