Field monitoring of a subsea shield tunnel during standpipe lifting

As a subsea construction method, the vertical lifting standpipe has been widely used for the construction of underwater intakes and outlets for hydraulic tunnels since it was applied in China in 1974. During the standpipe construction process with an opening tunnel ceiling, the lifting counter-force will act on the bottom of the tunnel and impact the internal forces and deformations of the close segments and joints of the tunnel. Because of the risk to monitoring personnel and the narrowness of the construction space, there is shortage of field monitoring data to testify or improve the design, and previous work was mainly concentrated on the numerical simulation of vertical lifting construction without field monitoring testification. In this work, the internal stress and joint deformations of the segment during the lifting process were monitored in the standpipe lifting project of the Liuheng power plant hydraulic tunnel and compared with the numerical simulation. The monitoring data figured out the behaviour of the segments and joints during the lifting process and provided a good proof for the rationality of the numerical simulation to improve the design.