【作者】 胡日军；

【导师】 吴建政；

【作者基本信息】 中国海洋大学 ， 海洋地质， 2006， 硕士

【摘要】 海底沙波是指海底床面沉积物为适应水流剪切作用而产生变形、从而使床面发生规则变化的特征形态,代表了典型的沉积物-流体系统的相互调整性质,一般分布在水动力较强和底砂充足的区域。南海北部水深100～250m的陆架和陆坡斜坡海底分布着大片沙波地貌,沙波波高在0.3～3m之间,波长数米～数十米,波形一般以不对称居多,缓坡向NW,陡坡向SE,波脊线大都沿NE～SW方向延伸。中型沙波和大型沙波两翼及谷部发育有次一级的小型沙波或沙纹,他们形态细小、排列紧密,形成复式沙体。本文采用底形相图参数近似计算和泥沙起动流速两种计算方法,结合海底沙波地貌的实际形态,分析了沙波的成因机制。采用数理计算方法分析了沙波在风海流和潮流的联合作用下的迁移速度和方向。根据实测资料、波浪和流的数值模拟资料从陆架底流速、陆架水深、陆架底砂和海底地形四个方面研究了沙波的形成发育条件。分析结果表明,研究区的沙波符合现代水动力条件,应属于现代沉积地貌而非残留沉积地貌;在风海流和潮流的联合作用下,沙波从总体上来看是向海(SE方向)移动的,由细砂、中细砂和中砂组成的沙波一天最大移动距离分别为5.1～10.2cm、2.4～4.8cm和1.5～3.1cm,迁移速率较小,对海底工程威胁不大;研究区内有足够大的底流速为沙波的形成提供了水动力条件,有充足的砂源、适宜的颗粒粒径和平缓的海底坡度为沙波的形成和发育奠定了物质基础,因此,研究区具备了良好的沙波形成发育条件,有利于沙波的形成和迁移。研究区具有丰富的石油和天然气资源,近年来,随着海洋资源的开发,在海底铺设了大量油气管线和海底电缆。同时,本区属热带海洋季风气候,是台风多发区域,突发事件如台风、海啸等都会对沙波的迁移和形态产生重要影响,造成海底地貌的重大变化。因此,通过对研究区沙波的形成机制、迁移和发育条件的详细了解,一方面可以丰富沙波的相关研究,另一方面对于保证海上安全生产、海洋设施的完整具有重要的实际意义。更多还原

【Abstract】 Sandwaves on seafloor is a kind of characteristic forms where sediments are deformed by current shear function and seabed is regularly transformed correspondingly. They are generally found in the region where there are powerful dynamic conditions and ample sediments and represent a typical character that sediments and liquid adjust one another.A large area of sandwave geomorphology has been found on the seafloor of the outer continental shelf and upper slope within a water depth of 100～250 meters in the northern South China Sea. Wave height of the sandwaves is 0.3～3m and wave length is a few meters long. They usually have anisomerous waveform with gentle slope to NW and steep slope to SE and the wave ridge line is in the direction of extending NE～SW. Second-clas sandwaves and ripples with a small geometry are developed in the two wings and wave hollow of medium to large sandwaves, and comprise duplicate seafloor sandwaves with medium to large sandwaves.Plenty of petroleum and natural gas have been found in the outer continental shelf. Recent years, with the development of marine resources, a lot of pipelines and seabed cable have been laid. At the same time, the study area is tropical marine monsoon climate with typhoon-prone region, incidents such as typhoon and tsunami will have an important effect on sandwaves motion and adjust and cause seabed to change greatly. Consequently, particular study on motion of sandwaves, mechanism of formation and conditions for growth, on one hand, makes study on sandwaves more abundant, on the other hand, have practical meaning for security of manufacture on the sea and integrity of marine establishment.Approximate calculation for bedform stability parameter and incipient motion of sediment combined with actual configuration of seafloor microtopography are adopted to study the mechanism of formation. Mathematical analysis is adopted to study motion velocity and direction of sandwaves so as to analyse stability of sandwaves.更多还原