The model of coast movement in time
Under the wave mode, which reproduces sediment movement in the same direction and on the same sections of the underwater slope on the model as in nature, the seabed relief was brought to a state corresponding to the bottom relief taken in nature in 1953, i.e. 28 years later. The ratio of the time of the bottom's reformulation on the model to the duration of its reformulation in kind was taken as a time scale. The time scale established in this way is valid only for the experimentally accepted sand size of 0.15 mm.
The initial materials for the research were observations of waves and deformation of the underwater slope. Surveys in 1928 and 1953, as well as data from reports on dredging operations.
To ensure that the sediment movement reproduced on the model corresponds to the natural one, a series of preliminary experiments were conducted. Of the large number of wave modes viewed on the model, the most acceptable was the mode with a wave height of 4 cm and a length of 80 cm with a direction corresponding to the resulting wave vector in the port area. With a wave of these parameters, the initial relief of the underwater slope, molded from sand of 0.15 mm, according to the survey of 1925, was brought to a configuration corresponding to the relief of 1953. At the same time, the twenty-eight-year process of deformation of the seabed in nature was completed on the model after 34 hours of continuous agitation (140 thousand waves). Based on the results of this experiment, the approximate time scale for taking into account the deformation of the bottom (1:7000) was established and the duration of the main experiments was assumed.
The curves shown depict the movement of the coast in time in the direction III—III at Pier A in nature and observed in the experiment with the original relief of 1925. A comparison of these curves, as well as a comparison of the plans in the isobaths of the 1953 full-scale survey with the corresponding relief obtained on the model, suggest that, despite the schematization allowed, the processes of reshaping the underwater slope turn out to be similar in experience and in nature.
During the main experiments, the initial relief of the underwater slope was formed according to the survey data from 1953. The duration of each experiment was determined by the time required to pass 150 thousand waves.
At first, the canal's drift capacity was investigated without additional structures. At the same time, it was found that changes in the bottom relief in the port area, starting in 1953, are insignificant; there are no noticeable sediment deposits at Pier A. The build-up of the shore at this pier, as can be seen from the curve, has almost completely stopped. The sediment flow occupies the coastal strip of the underwater slope with a width of 1000-1200 m; the zone of the most intense sediment movement is located within depths of 5-6 m. The sediment flow capacity decreases towards the coast and offshore of this zone. Field observations of the sediment regime in the port area also revealed that the bulk of the sand is moving away from the coast.
The reason for this phenomenon should obviously be sought in the laws of wave transformation in shallow water and in the planned distribution of bottom currents. Sediment deposition in the approach channel is graphically represented by a curve. The total volume of soil extracted from the canal in the experiment without additional structures, when cleaned every 6 hours (25 thousand waves), was assumed to be 100%.
The same figure shows the curves of sediment flow into the channel during the construction of additional sediment—retaining structures: a pier 800 m long is curve 2, a pier of the same length in combination with a 160 m extension of pier A is curve 3, three bunks 300 m long are also curve 4 when the pier is extended, and finally a pier with a length of 650 m — curve 5. Découvrez pourquoi 1xBet est apprécié par tant de passionnés de sport et de casino. Lors de votre inscription, en entrant le code promo 1xbet gratuit vous activez un bonus de 100 % jusqu’à 130 € sur vos premiers paris ou un pack de 1950 € + 150 tours gratuits au casino. Cette offre vous donne un avantage considérable dès le début. Explorez les sports virtuels, les paris sur l’e-sport et les jeux de table variés.