浪流耦合对汕尾港台风风暴潮模拟的影响

利用浪流耦合的无结构网格嵌套海洋模式,选取对汕尾沿岸海域影响较大的两次台风风暴潮过程进行模拟,分析浪流耦合作用对汕尾风暴潮增水的影响。结果表明:考虑浪流耦合的影响不仅能够将汕尾港风暴潮主振阶段的增水模拟误差减小5～10 cm,而且可以更好地刻画出港内增水的双峰结构,使得模拟结果的增水峰值时刻准确度提高近1 h。进一步的分析发现,汕尾港内浪致增水过程先于大风、低压引起的增水过程。同时,流场结果的对比表明:在风暴潮主振过程期间,浪流耦合作用对红海湾内的流场影响较为稳定,而对汕尾港入海口的流场影响较大。研究结果对防灾减灾和应急搜救工作有一定的参考意义。     

江苏省洋口港风暴潮数据分析

主要对江苏如东燃气电厂厂址(如东县长沙港海堤外)所在洋口港进行了风暴潮数据分析及对厂址影响评价。通过对风暴潮影响规律和历史强风暴潮过程灾情分析,仔细研究了相关特征潮位与潮位重现期和波浪爬高计算,确定了厂址区域的警戒潮位。研究认为:现有的堤防工程能够抵御重现期为200a一遇的风暴潮过程的堤防设计标准要求。     

胜利油田海堤风暴潮致损初始机制与过程分析

海堤损毁严重威胁着沿海地区人民生命财产安全和油气田正常运行。台风风暴潮期间有越浪时,海堤损毁发生迅速,海堤致损初始机制和破坏过程难以掌握。本文依据“利奇马”台风风暴潮期间损毁的东营胜利油田桩12海堤,建立室内物理模型,对海堤破坏的致损初始机制和破坏过程进行研究。结果表明：在堤顶路面发生破坏和不发生破坏两种工况下,堤内掏蚀空洞的发育情况是台风风暴潮使海堤损毁的重要因素,波浪经空洞对斜坡护面的浮托和推动,使得下部堆积散体暴露并被波浪冲走。通过本次室内模型试验,明确海堤致损初始机制,直观展示海堤破坏过程,为后续油气田海堤修复、修建工作提供数据支撑和理论依据。     

决口海堤水波传播模拟和分析研究Ⅱ:2D传播

应用经验证的SWASH数学模型,分析了海堤决口中心线沿线实测水深分布规律和保护区淹没水量与淹没面积。对不同特征水深进行验证,进而探讨不同波要素对不同形式的海堤决口堤后特征水深分布情况以及波浪传播距离与时间的关系;分析了物理模型试验中海堤决口宽度以及不同波要素对堤后洪水波演进的影响;计算了不同决口深度和宽度对洪水波传播的影响,建立堤后水体淹没水量和淹没面积分布公式。成果可供我国沿海城市和地区在风暴潮和台风浪作用下海堤决口风险图绘制参考。     

黄河三角洲滩涂区海堤护岸结构方案优化实证研究

海堤护岸是抵御和减轻风暴潮灾害的根本措施,是从根本上消除风暴潮对沿岸人民生命财产安全威胁的最有效措施之一。黄河三角洲沿海滩涂广阔平坦,多为沙质和淤泥质,沟壑交错,海堤护岸的建设量大面广,所以对区域内海堤护岸的建设方案进行比较优化,更显得十分必要。文章通过具体的工程案例,阐述了建于黄河三角洲滩涂区的海堤护岸结构方案的比选与优化步骤与方法,这无疑对建于滨海滩涂区的海堤护岸的方案优化具有直接的参考与借鉴意义。     

福建沿岸天文潮-风暴潮-台风浪耦合漫堤预警系统

基于SWAN模式和MATLAB GUI软件建立了福建沿岸天文潮-风暴潮-台风浪耦合漫堤预警系统。该系统包含天文潮-风暴潮-台风浪耦合计算模式和海堤预警显示两部分:天文潮-风暴潮-海浪耦合水位计算采用自主研发的FETSWCM模式(Finite Element Tide-Storm Surge-Wave Coupled Model),台风浪计算采用SWAN模式(Simulation WAve Nearshore),耦合计算时FETSWCM为SWAN提供风场、水位场及流场,SWAN为FETSWCM提供波浪辐射应力;海堤预警显示基于MATLAB GUI软件交互界面,根据模式计算波浪爬高所及高程结果(天文潮-风暴潮耦合水位与波浪爬高的和)对福建沿岸海堤进行可视化预警报。使用该系统进行两场台风过程福建省沿岸的漫堤后报检验,结果表明:1312号台风过程7条海堤及1319号台风过程东山县8条海堤漫堤预警准确率为87%。     

福建沿海浪潮耦合漫堤风险评估:以台风天兔为例

漫堤是天文潮、风暴潮与海浪等物理要素作用于海堤后海水翻越海堤的物理过程。本文利用天文潮-风暴潮-台风浪耦合模式(ADCIRC+SWAN)、基于非结构三角形网格和高分辨率地理数据(海堤位置和高程、岸线和水深等)构建福建沿海精细化漫堤风险等级评估系统。该系统在近岸网格分辨率最高达50m,可精确刻画福建沿海复杂地形。利用模拟的水位与海浪参数,采用波浪爬高公式计算得到各海堤堤前波浪爬高。按照总水位与波浪爬高之和与海堤高程的对比,将漫堤风险分为五个等级。对2013年的超强台风天兔过程进行后报检验。结果显示,该系统计算的漫堤情况与灾后调查的漫堤实况基本一致,结果准确,说明本研究中采用的漫堤风险评估标准和方法是可行的。在此基础上,设计了4种不同的台风强度等级,对福建沿海206条海堤进行了漫堤风险等级评估,探究台风强度对漫堤风险的影响。结果表明:波浪爬高对漫堤风险的影响高于单纯的风暴潮增水;风暴潮增水随台风强度的增强增量较小,对于漫堤的风险影响较小;福建沿海波浪爬高普遍较高,随着台风强度的增强,波浪爬高会显著增加漫堤的风险等级,且应重视台风浪对海堤造成的冲击所导致的溃堤灾害。本研究可为沿海防灾减灾提供科学依据。     

龙口港极端设计水位的组合估计

传统的单因素极端设计水位计算方法忽略了天文潮位与风暴潮增水的联合作用.已经提出的天文潮与风暴潮增水的组合方法,也未能把二者当作相关的事件来考虑.选取龙口港连续25 a风暴潮增水和天文潮位资料,采用二维Log-normal理论分布进行计算,估计了多年一遇风暴潮增水与天文潮位的联合重现值,所得极端水位可供海岸防灾部门作为设计参考.     

普陀沿海风暴潮淹没危险性评估

基于ADCIRC模型,建立了1套适用于舟山市普陀区的高分辨率风暴潮漫滩数值模式,对历史上影响该海域最严重的台风——9711号"维尼"进行风暴潮过程模拟,结果与实测吻合良好。以9711号台风路径为基础,构造了对普陀区沿海最有利增水的台风路径,并设定了5个不同强度的天气系统,充分考虑海堤对风暴潮淹没的影响,模拟得到了不同强度等级下普陀沿海风暴潮的最大可能淹没范围。结果表明,将风暴增水叠加到当地的天文高潮位上时,普陀区本岛区域和六横岛地区都存在着风暴潮淹没风险,水位均超过了当地的警戒潮位线,由于其近岸区海堤内的高程普遍较低,一旦出现海水漫堤的情况,将在普陀主城镇区发生大面积的淹没,淹没水深最大达2.5m左右,淹没面积达到26km2。     

渤海风暴潮对沿岸增水的影响及灾害风险评估

近10多年来,我国围填海工程发展迅速,渤海海岸线变化明显,岸线变化会改变潮波传播并影响风暴潮增水。基于FVCOM海洋动力学模型,利用潮汐和风场强迫,建立了渤海风暴潮模型,根据2000年岸线和2010年岸线,分别模拟了包括台风风暴潮和寒潮风暴潮在内的4次典型风暴潮过程,对模拟数据和实测数据进行统计分析,模拟结果与实测数据基本一致。研究了岸线变化前后,渤海风暴潮对近岸増水的影响,并对曹妃甸港、天津港和黄骅港的风暴潮增水灾害进行了风险评估。     

Microbial Biomass and Organic Nutrients in the Deep-Sea Sediments of the Central Indian Ocean Basin

In order to assess the impact of deep-sea mining on the in situ benthic life, we measured the microbial standing stock and concentration of organic nutrients in the deep-sea sediments of the Central Indian Ocean Basin in the Indian pioneer area. Sediments were collected using box core and grab samples during September 1996. The total bacterial numbers ranged from 10 10 -10 11 cells per g -1 dry weight sediment. There was a marginal decrease in the number of bacteria from surface to 30 cm depth, though the subsurface section registered a higher number than did the surface. The highest numbers were encountered at depths of 4-8 cm. The retrievable number of bacteria were two orders less in comparison with the direct total counts of bacteria. An almost homogeneous distribution of bacteria, total organic carbon, living biomass, and lipids throughout the depth of cores indicates active microbial and benthic processes in the deep sea sediments. On the other hand, a uniform distribution of total counts of bacteria, carbohydrates, and total organic carbon in all the cores indicates their stable nature and suggests that they can serve as useful parameters for long-term monitoring of the area after the benthic disturbance. Further studies on temporal variability in this region would not only verify the observed norms of distribution of these variables but would also help to understand restabilization processes after the simulated benthic disturbance.     

Assessing the Validity of Seismo-Acoustic Predictor Equations for Obtaining Seabed and Sub-Surface Sediment Physical Properties

The interdependence between the seismo-acoustic properties of a marine sediment and its geotechnical/physical parameters has been known for many years, and it has been postulated that this should allow the extraction of geotechnical information from seismic data. Though in the literature many correlations have been published for the surficial layer, there is a lack of information for greater sediment depths. In this article, a desktop study on a synthetic seafloor model illustrates how the application of published near-surface prediction equations to subsurface sediments (up to several tens of meters burial depth) can lead to spurious predictions. To test this further, acoustic and geotechnical properties were measured on a number of sediment core samples, some of which were subjected to loading in acoustically-equipped consolidation cells (oedometers) to simulate greater burial depth conditions. For low effective pressures (representing small burial depths extending to around 10 meters subsurface), the general applicability of established relationships was confirmed: the prediction of porosity, bulk density, and mean grain size from acoustic velocity and impedance appears generally possible for the investigated sedimentary environments. As effective pressure increases through, the observed relationships deviate more and more from the established ones for the near-surface area. For the samples tested in this study, in some instances increasing pressure even resulted in decreasing velocities. There are several possible explanations for this abnormal behavior, including the presence of gas, overconsolidation, or bimodal grain size distribution. The results indicate that an appropriate depth correction must be introduced into the published prediction equations in order to obtain reliable estimates of physical sediment properties for greater subsurface depths.     

海上大直径钢管桩打桩过程中桩周土强度弱化研究

海上大直径钢管桩打桩过程中,桩周土体受到强烈扰动而发生强度弱化,掌握桩周土体强度弱化规律对于准确预测打桩过程、保证工程安全具有重要意义。为研究土体强度弱化规律,开展了环剪试验模拟打桩对桩周土体的扰动,测试土体强度随剪切速率的变化规律,建立了描述土体强度弱化规律的拟合公式,引入到打桩分析软件中。研究结果表明：土体的强度折减程度不仅与土体本身的性质有关还受到土体的埋深和剪切速率的影响,埋深越深土体强度折减程度越低,剪切速率越高土体强度折减越高,在打桩分析中可采用这里推荐的线性折减方法来模拟不同深度处土体强度的折减规律。     

Geoacoustic Inversion via Genetic Algorithm and Its Application to Manganese Sediment Identification

An acoustic inversion method using a wide-band signal and two near field receivers is proposed and applied to multiple layered seabed models including a manganese sediment. The inversion problem can be formulated into a probabilistic model comprised of signals, a forward model, and additive noise. The forward model simulates wide-band signals, such as chirp signals, and is chosen to be the source-waveletconvolution plane wave modeling method. The wavelet matching technique, using weighted least-squares fitting, estimates the sediment sound-speed and thickness on which determination of the possible numerical ranges for a priori uniform distribution is based. The genetic algorithm is applied to a global optimization problem to find a maximum a posteriori solution for determined a priori search space. Here the object function is defined by an L 2 norm of the difference between measured and modeled signals. Not only the marginal pdf but also its statistics are calculated by numerical evaluation of integrals using the samples selected during importance sampling process of the genetic algorithm.     

Interannual Sea Level Variations and Annual Tides in the Northwestern Pacific

Specific properties of the interannual sea level variations and annual tides in the Northwestern Pacific were studied. Several tide stations were monitored. The monthly mean sea level for the year of 1995 was analyzed at each tide station. A seismic event in 1995, some tectonic activity around the subject area, and the Kuroshio (the oceanic western boundary current) may possibly contaminate results which would have occurred from the astronomical annual tide alone.     

Deep-Sea Sediment Compression Curves: Some Controlling Factors, Spurious Overconsolidation, Predictions, and Geophysical Reproduction

Oedometer tests have been carried out on 70 undisturbed surficial clays (at approximately 250 mm below the mudline), mostly collected by free-fall corers from sites widely scattered throughout the deep-sea North Atlantic. Acoustic measurements were also made, initially on contiguous samples and ultimately on the same sample using a geophysically instrumented oedometer which also collected electrical resistivity data. Apart from those quiescent areas below the carbonate compensation depth, such as north of the West Indies where very fine clays exist, most of the samples are silty clays whose geotechnical-geophysical properties are dependent on the type of clay minerals present (and their ability to take in moisture), the sand-size fraction, and the quantity of carbonate present. Thus the pure clays have high compressibilities which decrease on the addition of coarse particles, while the converse is true for the acoustic parameters, these increasing with the sand fraction. Using the notion of the intrinsic compression line for all samples, and comparison to it of the measured compression curves, it is clear that, contrary to some previously held ideas, most deep-sea clays are normally consolidated; the addition of carbonate has the effect of creating an open, stronger sediment skeleton. Interestingly, where information is available, the variation with depth of a sample's acoustic velocity follows the void ratio pressure relationship of the compression curve. This allows the construction of an in-situ sediment compression curve using the in-situ geophysical observations.     

Phylogenetic diversity and phenotypic characterization of cultivable bacterioplankton isolated from polar oceans

A set of 27 marine planktonic bacteria isolated from the polar regions was characterized by 16S rDNA sequencing and physiological and biochemical testing. More than half of these bacteria were positive for caseinase, gelatinase and 13-glucosidase, and could utilize glucose, maltose or malic acid as carbon source for cell growth. Twelve isolates expressed nitrate reduction activities. Except for one antarctic isolate BSwlO175 belonging to Actinobacteria phylum, these isolates were classified as γ-Proteobacteria, suggesting that γ-Proteobacteria dominated in cultivable marine bacterioplankton at both poles. Genus Pseudoalteromonas was the predominant group in the Chukchi Sea and the Bering Sea, and genus ShewaneUa dominated in cultivable bacterioplankton in the Prydz Bay. With sequence similarities above 97%, genus Psychrobacter was found at both poles. These 27 isolates were psychrotolerant, and significant 16S rDNA sequence similarities were found not only between arctic and antarctic marine bacteria （ 〉 99% ）, but also between polar marine bacteria and bacteria from other aquatic environments （ ≥ 98.8% ）, including temperate ocean, deep sea, pond and lake, suggesting that in the polar oceans less temperature-sensitive bacteria may be cosmopolitan and have a bipolar, even global, distribution at the species level.     

Flow Cytometric Analysis of Coastal Lagoon Bacterioplankton and Picophytoplankton: Fixation and Storage Effects

The effect of different fixation and storage protocols on the flow cytometric (FCM) simultaneous analysis of bacterioplankton and phytoplankton in coastal seawater samples (Mediterranean coastal lagoons) was investigated. FCM measurements (cell number, fluorescence and scatter characteristics) were obtained through DAPI staining. Three fixatives [glutaraldehyde (GA), formaldehyde (FA) and paraformaldehyde (PFA)] and two storage (3 months duration) methods (5 °C and −196 °C) were tested. Two dominant populations were detected in studied samples: bacteria and eukaryotic picophytoplankton. Adding fixatives (2% final concentration) appears necessary to obtain FCM exhaustive counts of all the bacteria and phytoplanktonic cells. This was related to the permeation effect of fixatives which allowed a better DAPI staining of the cells. Maximum fluorescence, i.e. optimal staining of the cells was obtained with FA or PFA, and significant lower fluorescences with GA. Fixed samples stored at 5 °C induced rapid cell loss. Only storage in liquid nitrogen of samples fixed with FA or PFA, allows mid-term (≥4 months) preservation of bacteria or picophytoplankton cell numbers, and limited evolution of DAPI-induced fluorescence and scatter characteristics.