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In the leveling construction of gravel bed of Dalian Bay subsea tunnel, sonar system plays an important role, which can accurately detect the laying quality of gravel bed, but the measurement accuracy of sonar is easily affected by ranging. In order to study the influence degree of different ranging on sonar in water and determine the sonar ranging range that is most suitable for the acceptance of the leveling ship, this paper uses the acceptance method of fully lifted gravel bed of the leveling ship to analyze the influence degree of different ranging degrees of sonar in the leveling ship on the acceptance accuracy by changing the height of sonar ranging in water, so as to obtain the optimal ranging range of sonar in water during the acceptance. The conclusions obtained are used to provide a basis for subsequent gravel bed leveling construction and gravel ridge acceptance of pipe sections. [ABSTRACT FROM AUTHOR]

Due to the limitation of engineering terrain and topography, large-scale immersed tube tunnels need to adopt curved immersed tube to control tunnel alignment, which is greatly affected by curvature radius. The immersed tube in the curved section of Dalian Bay Subsea Tunnel adopts the largest curvature in China（curvature radius of 1 050 m） for tunnel alignment fitting. For analyzing the differences between large curvature immersed tube and straight line tube section in the aspects of prefabrication, anchor system layout, sinking, ballast, pull-in, hydraulic crimping, etc, and put forward solutions. Through sorting out different points, theoretical calculation, process optimization and practice verification, a number of technical problems in the installation of large curvature immersed tubes have been solved, and key technologies in the installation of large curvature immersed tubes have been formed. [ABSTRACT FROM AUTHOR]

The elevation system of a leveling ship is particularly important for the leveling operation. The accuracy of the system directly affects the accuracy of leveling and the installation of immersed tubes. This paper gives mainly the method and process of a total station to check the leveling elevation system, analyzes comprehensively the checking data in different time periods according to the checking data, and then studies the factors, time periods and leveling accuracy that affect the checking accuracy, so as to determine the optimal checking method and means. With the checking method and the elevation system corrected, the leveling accuracy is further improved and, during the construction of Dalian Bay Subsea Tunnel project, the maximum deviation of the elevation at the head of an immersed tube is 11 mm after its installation and the maximum deviation at the tail is 13 mm, with its through-survey results meeting the design requirements. The successful application of this checking method can provide guidance and reference for later leveling operations and checking with similar systems. [ABSTRACT FROM AUTHOR]

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In order to study llie feasibility of first bedding method of the gravel bed and the silling capacity of the gravel bed in Shenzhen-Zhongshan passageway project, we carried out the gravel bed leveling and siltation observation tests in the test trench of Shenzhen-Zhongshan passageway. In this paper, we mainly introduced the leveling of the base bed with different gradations and the furrow width in the test tunnel, and used the silting box, scuba diving exploration and multi beam to monitoring the siltation, and then studied and analyzed the siltation strength of the foundation trench, the silting capacity of the gravel bed and the effect of the flat vessel inserting pile on the stability of the slope. Through the experimental study, it is shown that the silting capacity of different graded gravel beds is more than 13 days. The gravel bed scheme of the first bedding method is feasible in the Shenzhen-Zhongshan passageway, the silting capacity of the gravel bed can meet the requirements of the period of the installation window of the immersed tube, and has great guiding significance for the design and construction of the later cushion plan. [ABSTRACT FROM AUTHOR]

Foundation treatment is very important in the construction of immersed tunnel. It can ensure the deformation stability of tunnel during construction and operation period. With the development of the equipment manufacture, the method of pre laying and leveling came up and was applied to the foundation construction of immersed tunnel. It has high construction accuracy, fast laying speed, high degree of automation, safety and controllability. Its function can greatly increase the bearing capacity of the weak foundation, play the role of the diffusion stress, and drain and accelerate the consolidation and settlement of the lower soil layer. We expounded the application and development of the pre laid leveling technique in worldwide of the immersed tunnel, which will provide reference for similar projects. [ABSTRACT FROM AUTHOR]