Research On The Hydraulic Conditions In The Process Of Cofferdam Blocking-off

Cofferdam blocking-off is one of the most important steps in the cofferdam works. In the process of cofferdam blocking-off, very severe hydraulic conditions often occur when the breadth of entrance is shortening, the elevation of the submerged dyke goes up and the tidal level of outer sea varies with time. In order to ensure successful implementation of blocking-off, it is necessary to have good understanding of the hydraulic characteristics, upon which suitable scale for the entrance may be determined and proper procedure of blocking-off may be maintained. Hydraulic calculations for the second phase project of the blocking-off works of the Southeast End Cofferdam of the Caofeidian Port are performed and the main achievements are summarized as follows:(1)By using the weir flow theory, hydraulic calculations are conducted and analysis is carried out for the velocity variation in different phase of shortening of the entrance and uprising of the submerged dyke. Some principles are proposed for the determination of the procedures in the blocking-off works.(2)The 2D shallow water numerical model ADCIRC is used to simulate flow process in the cofferdam blocking-off. The model is verified by comparing the simulated results of water level and velocity with the measured ones. Velocity fields at high tide and ebb tide are obtained.(3)Comparisons have also been performed between the hydraulic results obtained by the two different methods and some useful suggestions are proposed for practical applications.