Aluminum alloy sacrificial anodes applied to protect the subsea immersed tunnels' steel shells are buried in an unfamiliar inhomogeneous backfilled stone/brine media. To verify its influence, the effect of the backfilled stone (10–12, 6–10, and 3–6 mm)/brine (40 Ω cm) media, denoted as Stone 1, Stone 2, and Stone 3, on the initial electrochemical performance of an Al─Zn─In─Si─Sn─Ti anode is investigated by electrochemical and surface analysis techniques. With decreasing the stone size, the Stones 1–3 media's resistivity increases to 100, 125, and 150 Ω cm, respectively. The backfilled stone/brine media inhibits the anode′s free corrosion and pitting process and accelerates its activation in the initial period. The anode′s capacity and current efficiency decrease slightly; however, the anode′s output current and its transmission are depressed more heavily by decreasing the backfilled stone size. Also, the backfilled stone shields parts of the cathode surfaces, decreases dissolved oxygen concentration, and blocks the diffusion of the anode's dissolution product in the media, resulting in the change of the anode's protective effect.

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From the aspect of calculation theory, the beam–spring model method and modified routine method of shield tunnel segment structure calculation were improved, and an efficient integrated software system for segment structure calculation of shield tunnel was developed. The beam–spring method is generally calculated according to the assumption of continuous displacement between beams and joints, and the existing modified routine method assumes that the lateral pressure gradient is constant generally, which does not consider the variation in lateral pressure gradient caused by the difference in the lateral pressure coefficient of soil layers or the water level height, which has a certain deviation from the actual situation. The existing beam–spring method and modified routine method theory were improved, the discontinuous displacement between beams and joints in the beam–spring method was taken into account, and the problem of lateral pressure gradient change in the modified routine method was solved. The calculation software system developed by C# and python programming language was proposed to improve the accuracy and efficiency of segment structure calculation. Based on the actual monitoring data of the internal force of the shield tunnel segment and the adjacent shield tunnel segments under construction in Changsha, China, the segments of the shield tunnel with different cross-section sizes and different hydrogeological conditions are calculated to verify the reliability of the calculation software system. At the same time, combined with the calculation results of the software system and field test data, the stiffness reduction coefficient and equivalent foundation resistance coefficient in the modified routine method were derived to further improve the accuracy of the calculation results, which provided a new idea for the calculation of segment structure of shield tunnel with different diameters under different hydrogeological conditions.

Precast pipe jacking construction technology has been widely applied in bridges engineering, however, the jacking technology in immersed tunnel is different from bridges, the former requires higher synchronization of pushing process and pushing performance of equipment. In particular, precast slide rail layout and selection of slide plate material will directly affect the effect of immersed tube tunnel. In this paper, based on the final pipe joint project of immersed tube tunnel in Shenzhen-Zhongshan Link, the research will not only carry out selection and parameter test of slide rail but also scale model test, which will further verify the engineering feasibility of the slide rail design scheme. The experimental result calculates the value range of friction coefficient of slide plate and points out the influence of machining deviation on slide rail, which provides strong support for parameters design and material selection.