Numerical Simulation of Hydrodynamic Conditions on Closure Gap of Immersed Tunnel in Hong Kong-Zhuhai-Macao Bridge

Abstract

The immersed tube method is adopted in the Hong Kong-Zhuhai-Macao Bridge. Before the final joint is installed, a closure gap will be formed in the middle of the immersed pipes. The closure gap underwater has its own characteristics of water current. In this article, a 3D mathematical model of water flow in the local waters of the closure gap is established, and the flow structure in the closure gap area is simulated, and the relationship of the water flow velocity with the Pearl River runoff and the tidal range is worked out. The simulation results show that the velocity distribution in the vertical section of the closure gap is present that the surface velocity is greater than the bottom and the velocity of ebb tide is greater than that of flood tide. The closure gap water flow increases with the increase of the tidal range under the same runoff, and the flow velocity increases with the increase of the upstream runoff under the same tidal range. The crane ship used in the final joint installation is only 30m away from the closure gap area. The deflecting flow from the ship’s bow makes the flow velocity increased sharply on the west side of the closure gap, but it has less influence on closure gap water flow conditions. According to the numerical simulation results of the hydrodynamic conditions in the closure gap, the external water conditions and the appropriate time for the final joint installation are confirmed. The technical support of the final connection is provided for the project of Hong Kong-Zhuhai-Macao Bridge.