海底输油管道底砂床冲刷机理研究     

吴钰骅  金伟良  毛根海  张恩勇  粟京 《海洋工程》2006,24(4):43-48

设计了海底输油管道水槽冲刷试验模型,研究了海底输油管道与砂床处于不同相对位置情况下床砂起动流速的变化,采用理想流体映射定理对其进行了理论分析,探讨起动流速变化规律。结合有限元数值模拟对试验进行细化分析,研究了海底管道底砂床砂粒起动的产生机理,根据研究结果将冲刷过程划分为五个阶段。阐明了海底管道暴露冲刷的危害性和实时监测的重要性。  相似文献   

The impact of shrimp trawling and associated sediment resuspension in mud dominated, shallow estuaries     

Timothy M. Dellapenna  Mead A. Allison  Gary A. Gill  Ronald D. Lehman  Kent W. Warnken 《Estuarine, Coastal and Shelf Science》2006,69(3-4):519

To address the relative importance of shrimp trawling on seabed resuspension and bottom characteristics in shallow estuaries, a series of disturbance and monitoring experiments were conducted at a bay bottom mud site (2.5 m depth) in Galveston Bay, Texas in July 1998 and May 1999. Based on pre- and post-trawl sediment profiles of ⁷Be; pore water dissolved oxygen and sulfide concentration; and bulk sediment properties, it was estimated that the trawl rig, including the net, trawl doors, and “tickler chain,” excavate the seabed to a maximum depth of approximately 1.5 cm, with most areas displaying considerably less disturbance. Water column profile data in the turbid plume left by the trawl in these underconsolidated muds (85–90% porosity; <0.25 kPa undrained shear strength) demonstrate that suspended sediment inventories of up to 85–90 mg/cm² are produced immediately behind the trawl net; an order of magnitude higher than pre-trawl inventories and comparable to those observed during a 9–10 m/s wind event at the study site. Plume settling and dispersion caused suspended sediment inventories to return to pre-trawl values about 14 min after trawl passage in two separate experiments, indicating particles re-settle primarily as flocs before they can be widely dispersed by local currents. As a result of the passage of the trawl rig across the seabed, shear strength of the sediment surface showed no significant increase, suggesting that bed armoring is not taking place and the trawled areas will not show an increase in critical shear stress.  相似文献   

南海高钙沉积物中18种常微量元素的ICP-AES测定方法研究     

王湘芹  陈志华  任红  孙琼 《海洋科学进展》2007,25(2):220-225

在利用ICP-AES分析南海高钙沉积物中的常微量元素时,钙、镁常常干扰其它元素测试。通过采用优化仪器工作参数、扣除背景值、谱线干扰校正和基体匹配的步骤,消除了元素干扰和钙、镁基体效应,提高了方法的灵敏度和准确度。通过对南海沉积物样品的大量实验和国家一级标准样验证,建立了适宜高钙海洋沉积物元素含量的ICP-AES测试方法。该方法检出限为1.55~271μg/L,相对标准偏差RSD<4.54%(n=6)。  相似文献   

Immediate profile and planform evolution of a beach nourishment project with hurricane influences   总被引：1，自引：0，他引：1  

Nicole A. Elko  Ping Wang 《Coastal Engineering》2007

In this study, planform adjustment began during a period of calm weather immediately after nourishment and then the passage of one strong storm caused a substantial portion of the total profile equilibration. Weekly beach profiles, shoreline surveys, and nearshore wave measurements were conducted before, during, and immediately after construction of the 1100-m long Upham Beach nourishment project on the low-energy, west coast of Florida. This project was constructed in three segments: the wide north segment, the central segment, and the narrow south segment. With the exception of the relatively distant passage of Hurricane Charley, calm weather prevailed for 45 days following completion of the south and central segments. Construction of the wide north segment was completed on August 27, 2004. Substantial planform diffusion occurred prior to construction completion via formation of a 300-m long spit extending from the wide north segment. The shoreline orientation was changed abruptly due to this diffusion spit formation, as opposed to the gradual adjustment predicted by most long-term models. Planform adjustment was initiated prior to profile equilibration, and it did not require high-energy conditions. A simple vector sum model for determining the orientation of a potential diffusion spit was developed. This study recommends designing end transitions at the predicted diffusion spit orientation to avoid post-nourishment spit formation during future projects.  相似文献   

Interstitial water chemistry of the inner continental shelf sediments off the gironde estuary     

H. El Ghobary 《Estuarine, Coastal and Shelf Science》1983,16(6)

The interstitial water composition ( , alkalinity, Ca²⁺, Mg²⁺, Sr²⁺, Na⁺, K⁺) and the cation exchange capacity (CEC) were determined for the muddy sediments of the continental shelf off the Gironde Estuary (France), in the area where the sediment represents the deposit of the muddy suspension of the river. In comparison with seawater concentrations, the pore waters below 10 cm depth, show depletions of and Ca²⁺ and below a 30 cm depth show depletions of Mg²⁺. Inversely, the upper 10 cm an enrichment of Ca²⁺ concentration, and an increase of K⁺ concentration to a 40 cm depth. High values of are observed at the top 4 cm. Alkalinity enrichment is observed along the length of the core. Applying the alkalinity models for the sediment below a 10 cm depth demonstrates generally that calculated alkalinities are higher than the measured ones. Ca²⁺ dissolution occurs at the first 10 cm and authigenic carbonate precipitation starts beneath that level. Mg²⁺ depletion is accompanied by bicarbonate loss. This proves that Mg²⁺ depletion is due to a Mg-silicate reaction. The result of the CEC does not confirm the Mg²⁺ uptake by clay minerals in exchangeable site, under reducing conditions. Diffusion and bioturbation play an important role in the pore water concentration at the top of the core.  相似文献   

Oxygen Uptake During Repeated Exposure to Temperature Change: Physiological Divergence in Panamanian Cognate Pairs and Latitudinally Distant Populations of Decapod Crustacea     

J. D. Ferraris  J. L. Norenburg 《Marine Ecology》1997,18(2):127-146

Abstract. The emergence of the Isthmus of Panama subdivided the amphi-American biota. In the present study, Pacific and Atlantic populations of four cognate pairs of crabs were used to discern whether exposure to different thermal regimes in habitats, in the putative absence of gene flow, has resulted in physiological divergence. Populations that potentially form a common genetic pool were also used; these were populations of the Atlantic Panama cognate that occur in Belize and Florida. Decreases in water temperature occur periodically in Pacific Panama and Florida, but not in Atlantic Panama or Belize. In this study, physiological divergence in oxygen uptake was assessed in response to repeated exposure to either control and decreased temperature or control and increased temperature. Results indicate that, in only some of the genera tested, exposure to decreases in habitat temperature has resulted in divergence. Partial support is found for the corollary that adaptation to an environment with periods of decreased temperature results in reduced compensation during exposure to elevated temperature.  相似文献   

南海南部大陆架的残留沉积   总被引：1，自引：0，他引：1  

吴时国  罗又郎 《热带海洋学报》1994,(3)

研究了南海南部大陆架的残留沉积物的粒度、石英砂表面结构特征、生物分布等，并指出残留沉积普遍遭受改造。按其早期的形成环境差异和改造作用不同，划分出加里曼丹－巴拉望残留沉积区和亚南巴斯－纳土纳残留沉积区。  相似文献   

Discussion on Coastal Erosion Near Xizhuang, Penglai, China   总被引：1，自引：0，他引：1  

Wu Guiqiu Li Wei Professor  First Institute of Oceanography  State Oceanic Administration  Qingdao Associate Researcher 《中国海洋工程》1994,(2)

-In this work, on the basis of the characteristics of coastal erosion near Xizhuang (Penglai, Shandong, China) and the in-situ measured data and theoretical calculation, the causes of coastal erosion there are obtained: (1) natural erosion, (2) beach sand borrowing, and (3) sand borrowing at the Dengzhou shoal near Xizhuang, which results in the loss of the function of the wave force resistance of the shoal. Since the wave energy is increased, the longshore sediment transport rate is increased. Coastal erosions are more and more serious. A scientific basis to reduced the calamity of coastal erosion in local area is presented. Some experiences are accumulated for studying coastal erosion.  相似文献   

Sediment Transport in Rivers and Coastal Waters     

YANG  Shu-qing 《中国海洋工程》2003,17(4):527-540

Following Bagnold's approach, a relationship between sediment transport and energy dissipation is developed. The major assumption made in the study is that the near bed velocity plays a dominant role in the process of sediment transport. A general relationship between energy dissipation and sediment transport is first proposed. Then the equations for total sediment transport are derived by introducing the appropriate expression of energy dissipation rate under different conditions, such as open channel flows, combination of wave and current, as well as longshore sediment transport. Within the flows investigated, the derived relationships are fairly consistent with the available data over a wide range of conditions.  相似文献   

耗氧速率(OUR)测量方法的实验研究   总被引：4，自引：0，他引：4  

李冰  孙英兰  李玉瑛 《中国海洋大学学报(自然科学版)》2006,36(3):456-460

目前多采用分批实验法和呼吸测量仪测量耗氧速率,而耗氧速率的测量对于研究活性污泥数学模型中的动力学参数及废水特性鉴定具有重要意义。本文根据OUR测量方法的基本原理设计了1种简易的OUR测量装置,为检验测量装置的有效性,设计了相关实验进行验证。在内源呼吸实验中,测定了所用活性污泥的内源呼吸速率是5.1mgO2/L·h,污泥的衰减系数是0.0137h-1,比文献值略高。基质降解实验对人工配水(葡萄糖和淀粉)的耗氧速率进行了测定,实验结果显示有3个显著不同的耗氧速率,分别为35mg/L·h,13mg/L·h,6mg/L·h,它们各代表葡萄糖降解、淀粉降解和内源呼吸的速率。内源呼吸速率高于前1个实验是由于基质降解过程中污泥量增加所致。并计算出异养菌产率系数Kd为0.63mgVSS/mgCOD,Kd略低于文献值。实验结果证明,该装置能很好的实现测量目的。  相似文献