The long-distance flotation of large-scale immersed tubes has consistently posed a substantial challenge in the construction of immersed tube tunnel projects.The Shenzhen-Zhongshan Link's immersed tube,for instance,necessitates a flotation distance of 50 km,which involves multiple channel transitions and faces huge construction risks.Physical model tests are carried out to examine the floating posture of the immersed tube under high-speed conditions.The in-situ measurement of immersed tubes' trim attitude is carried out in the construction of Shenzhen-Zhongshan Link.The results show that the maximum pitch angle of immersed tube can reach 0.27° at a floating speed of 5.12 kn in physical model tests.When following waves,the maximum pitch angle at the same floating speed decreases to 0.16°,and a notable water uplift phenomenon occurs at the top of the immersed tube during this phase.The actual measurement data align generally with the trends observed in the physical model tests.At an actual ship speed of 4.25 kn on-site,the measured maximum pitch angle of the immersed tube is 0.19°,affirming the conclusions derived from physical model tests.