钦州湾蓄泥坑泥沙扩散数值模拟

Numerical Modeling of Sediment Diffusion from a Mud-storage Pit in Qinzhou Bay

关键词:  钦州湾  蓄泥坑  ECOMSED  悬浮泥沙  潮流

Key words:  Qinzhou Bay  mud-storage pit  ECOMSED  suspended solid  tidal current

摘要:

[目的]近年来,钦州港的快速开发在带动海洋经济发展的同时,也对周围的海洋环境造成一定的压力,本研究试图寻找钦州湾海上工程产生的泥沙扩散对周围环境影响最小的施工方法。[方法]基于ECOMSED模型模拟钦州三墩作业区蓄泥坑开挖引起的水动力变化和泥沙扩散情景,通过敏感性实验测试了不同围挡实验对减少泥沙扩散面积的效果。[结果]发现钦州湾潮流场呈往复流特征,落潮流大于涨潮流。涨潮中间时大部分海域流向以偏北方向为主,最大潮流流速为1.85 m/s;落潮中间时大部分海域的潮流为偏南向,最大潮流流速为2.34 m/s。蓄泥坑的北部基本为西南向流,东部基本为南向流,南部和西部为东南向流。无论表层还是底层,蓄泥坑东北部的流场在工程前后变化较大,流速偏差约为10%,表层和底层的平均流向偏差分别为5.05°和4.55°。无围挡泥沙扩散实验中浓度为10 mg/L的悬浮泥沙包络线影响范围较大,可影响到保留区和航道。围挡实验中,东开口和西开口的泥沙扩散面积与无围挡实验基本相同。而南开口和北开口的泥沙扩散面积明显减小。[结论]采用三面围挡仅北端开口的施工方法可以显著降低泥沙扩散对周围海洋环境的影响。

Abstract:

[Objective] In recent years, while the rapid exploitation of Qinzhou Bay has led to the development of marine economic, it has also caused some pressure on the marine environment around it.Therefore, it is necessary to try to find out a construction method that has the least impact on the surrounding environment caused by the sediment diffusion from Qinzhou Bay marine engineering.[Methods] The ECOMSED model was utilized to simulate the hydrodynamic changes and the sediment diffusion caused by the excavation of mud-storage pit in Qinzhou Sandun working area, and the effect of different enclosure tests on the reduction of sediment diffusion area was tested by sensitivity experiments.[Results] It was found that the tidal current in Qinzhou bay was basically reversing current, and the ebb current was larger than the flood current.Most of the current direction was northward and southward in the mid-time of flood tide and ebb tide, respectively, with a maximum speed of 1.85 m/s and 2.34 m/s, respectively.The northern part of the mud-storage pit was basically a southwest current, the east was basically a south current, the south and the west were a southeast current.No matter the surface layer or the bottom layer, the currents to the northeast of the pit experienced the most significant changes before and after the project, with the velocity deviation of about 10% and the average deviation of the surface layer and the bottom layer being 5.05° and 4.55°, respectively.The suspended solid envelope with a concentration of 10 mg/L in the non-enclosure sediment diffusion experiment had a large impact range, which could affect the reserved area and the shipping lane.In the enclosure experiment, the sediment diffusion areas in the east and west gap were basically the same as that of the non-enclosure test.However, the area of sediment diffusion in the south and north gap decreased significantly.[Conclusion] Therefore, the affection of sediment diffusion on the marine environment will be sharply reduced when the construction method uses a three-sided enclosure with only the gap in the north.