Abstract: In order to improve the construction quality of tube segments during full-section casting of immersed tube tunnel, by taking an immersed tube tunnel project in Guangzhou as the background, the orthogonal design principle is adopted in this paper in combination with numerical simulation to systematically study the influencing laws and combined effects of hydration heat control measures such as the inlet water temperature, flow rate and water flow duration of cold water pipe, thermal insulation measures and pouring temperature on the temperature control indicators (the maximum temperature T_max and the maximum interior-exterior temperature difference ΔT_{ie_max}) and cracking risk indicators (the anti-cracking safety factor K_min) during the full-section casting process of immersed tube segments. A suitable and cost-effective temperature control optimization scheme for full-section casting of immersed tube segments is proposed. Research results show that: (1) Reducing the pouring temperature and prolonging the water flow duration can significantly decrease T_max and ΔT_{ie_max}, and reducing the thermal insulation measures can effectively decrease T_max but greatly increase ΔT_{ie_max}, while the inlet water temperature and flow rate have no obvious control effect. (2) Increasing the inlet water temperature, reducing the pouring temperature, and prolonging the water flow duration can reduce the cracking risk, while the flow rate and thermal insulation measures have relatively low sensitivity. (3) The roof above the corridor (peak temperature and temperature difference), the area around the inlet of cold water pipe (cracking risk due to high heat gradient), and the junction of the middle partition wall, and the floor (cracking risk due to geometric mutation) are the key areas for hydration heat control of tube segments during full-section casting, and shall be closely monitored. (4) On the site, the scheme with an inlet water temperature of 15 ℃, a flow rate of 2.0 m³/h, a water flow duration of 2 days and a pouring temperature of 25 ℃ was adopted, and thermal insulation was carried out under the condition of steel formwork. Under this scheme, the measured T_max of the tube segment was 64.57 ℃, and ΔT_{ie_max} was 24.16 ℃, both less than the limits specified in the relevant standards, and the cracking risk of immersed tube segments was effectively controlled.

Key words: immersed tube tunnel, full-section casting, orthogonal experiment, optimization of temperature control scheme, hydration heat, cracking risk