粉砂淤泥质海岸开敞航道淤积模式探讨

粉砂淤泥质海岸开挖的开敞航道,普遍存在淤积问题,而且在风暴浪作用过后,经常出现泥沙大量骤淤现象．根据已有的研究成果,指出航道淤积除存在悬移质淤积、推移质淤积、层移质淤积外,还有泥沙流滑淤积、航道侧面土体滑坡淤积2种方式,并概念性地分析了粉砂淤泥质海岸航道淤积．在常浪状况下,主要为“悬移质＋推移质＋层移质”的淤积组合模式;在风暴浪状况下,主要为“悬移质＋推移质＋层移质＋泥沙流滑＋航道侧面土体滑坡”的淤积组合模式。     

粉沙质海岸航道骤淤期悬移质挟沙力研究

悬移质挟沙力是粉沙质海岸航道骤淤预测的关键性参数,目前缺乏有效的研究成果。通过大尺度波浪水槽对缓坡下的粉沙质海岸骤淤期破波掀沙机理进行试验观测和研究,根据能量平衡原理,建立粉沙质海岸在崩破波作用下悬浮泥沙运动的能量平衡方程式。能量平衡方程式的要点在于波浪所提供的有效能量损耗中,除了传统的底摩擦损耗和悬浮泥沙所消耗的能量外,还应增加崩破波引起的能量损耗。在此基础上提出粉沙质海岸骤淤期悬移质挟沙力公式,并得到试验资料的初步验证。     

港湾深槽骤淤的条件探讨

深槽骤淤指深槽底部在特定条件下产生的快速淤积,通常以浮泥形式出现.综合分析杭州湾、三门湾和象山港的地形地貌、水文泥沙及深槽固定剖面风暴前后或大、小潮期间的地形变化得出港湾深槽产生骤淤的基本条件:(1)有丰富的细颗粒物质的供应源;(2)迅速衰减的动力条件;(3)存在明显的负地形.三个条件必须同时得到满足,深槽才能产生骤淤.杭州湾泥沙来源丰富,终年悬沙浓度高,东试挖槽附近受长江冲淡水次级锋面和钱塘江冲淡水锋面影响较大,因此在一个大小潮周期内水动力条件减弱时挖槽处可产生骤淤.三门湾泥沙来源较丰富,正常天气的年份内潮滩处于缓慢淤积状态,而深槽处于冲淤基本平衡状态,但在风暴等灾害性天气下发生强烈的滩、槽泥沙交换,若风暴后处于中小潮汛期则深槽发生骤淤.象山港由于环境隐蔽,水清沙少,沿岸潮滩狭窄,缺少骤淤的物源,即使风暴作用后鹰龙山深槽也没有产生骤淤.     

乐清湾港池开挖后骤淤可能性分析

乐清湾避风条件好,潮流动力强,含沙量小,具有较好的建港条件。通过对骤淤机理的分析和试挖槽在台风期间的监测以及大风浪下的悬沙淤积的估算等多种研究后,认为乐清湾港池开挖后不会发生骤淤,实行浅水深用的开发方案是可行的。     

珠江口伶仃洋航道的回淤分析

通过实测资料的统计分析，结合珠江口伶仃洋的动力地貌条件，对该航道的泥沙回淤特征进行了多方面的论证，得出回淤主要发生在航道开挖段北部，洪季淤积占全年2／3以及航道增深后回淤并未成比例增加等研究结果，指出了该航道进一步开发的前景。     

开敞式滩海油田保滩促淤工程研究

分析了飞雁滩油田海区的海洋环境条件,试验研究了不同结构型式潜堤的稳定性和保滩促淤效果,对潜堤的保滩促淤效果和淤积速率进行了预测,对工程布置、潜堤结构方案、基础冲刷防护措施和潜堤顶高程提出了建议．     

淤泥质、粉沙质及沙质海岸航道回淤统一计算方法

根据20世纪80年代初提出的淤泥质海岸航道回淤计算方法的基础上,开展了拓展研究,使之统一适用于淤泥质海岸、粉沙质海岸及沙质海岸。主要研究内容有,在波浪和潮流综合作用下挟沙力含沙量研究中引入了特定的泥沙因子F1/F,从而挟沙力含沙量公式不仅适用于淤泥质泥沙,也适用于非淤泥质泥沙;在动力因素方面,除了一般寻常潮和波浪动力外,进一步考虑了风暴潮和破波的巨大掀沙能力造成航道骤淤的可能性。并结合连云港30万吨级主航道扩建及徐圩港区10万吨级航道的回淤问题(包括骤淤可能性问题),京唐港外航道和黄骅港外航道的骤淤问题,进行预测计算及校验计算,结果都是良好的。此外,对杭州湾强潮和涌潮情况下的挟沙力含沙量也进行了校验计算,结果也非常满意。     

汕头柘林湾港区航道浚深后的回淤分析与计算

本文在取得大量实测和调查资料的基础上,对柘林湾的水文、泥沙条件作了归纳与统计;还着重对航道的回淤问题进行了分析,并提出了浚深后的回淤量预报值,可供在该海区今后建设深水港口时参考。     

象山港航道冲淤变化初步分析

利用象山港海湾不同年份的水深地形资料,运用GIS技术采用航道轴线剖面水深地形叠加对比和海床平面冲淤计算相结合的方法,应用以往水文泥沙等资料综合分析象山港航道区域的冲淤变化。结果表明40a来象山港航道区域总体冲淤基本平衡,大致以双德山附近海域为界,以东牛鼻山浅段和西屿山-双德山深段两区段以微淤为主,平均厚度分别为0.08~0.24m和0.51~0.58m,并具有缓慢淤积的趋势;以西的浅段和深段则以微冲为主,平均厚度为0.32~0.62m,并具有轻微冲刷的趋势。     

Relation Between Sudden Sedimentation and Wind Energy in Outer Channel of Huanghua Port and Its Application in Binzhou Port

Based on the analysis of ocean dynamic condition and sediment environment, conclusions can be drawn that strong wind is an essential factor influencing sudden sedimentation in outer channel. Through theoretical analysis, it changes the complex process that wind raises wave, wave tilts sediment and current transports sediment into a comprehensive factor, and obtains mathematical formula between effective wind energy and the thickness of sudden sedimentation. The parametees in this formula are determined with field data of Huanghua Port. It may be used to predict siltation thickness and volume along the channel. By analyzing and comparing the difference in ocean hydrodynamic conditions and seabed material between Huanghua Port and Binzhou Port, the proposed formula can be used to predict sudden sedimentation in Binzhou Port and the calculated results is rehable. By predicting it on different combination plans among different recurrence in- tervals, entrance locations and channel classes, it provides references for the plane design of Binzhou Port.     

Pullout Capacity of Horizontally Loaded Suction Anchor Installed in Silty Sand

Current floating structures require more reliable and higher anchoring capacities because of their increased size. A suction anchor is one of the most popular anchors for a floating system. In this study, the behavior of a suction anchor installed in cohesionless soil was investigated when the anchor was subjected to mainly a horizontal load. Three-dimensional finite element numerical analyses were carried out using ABAQUS, and three centrifuge tests were performed to calibrate the numerical analyses. A parametric study with different dimensions and loading points for the suction anchor was conducted. The horizontal capacity of the suction anchor was estimated, and the soil reaction distribution was analyzed when the load was applied at the optimal point. Based on the results, an analytical equation for calculating the horizontal capacity of a suction anchor was proposed that can be easily adopted for design.     

Hybrid Analysis Approach for Stochastic Response of Offshore Jacket Platforms

The dynamic response of offshore platforms is more serious in hostile sea environment than inshallow sea.In this paper,a hybrid solution combined with analytical and numerical method is proposedto compute the stochastic response of fixed offshore platforms to random waves,considering wave-struc-ture interaction and non-linear drag force.The simulation program includes two steps:the first step is theeigenanalysis aspects associated the structure and the second step is response estimation based on spectralequations.The eigenanalysis could be done through conventional finite element method conveniently andits natural frequency and mode shapes obtained.In the second part of the process,the solution of theoffshore structural response is obtained by iteration of a series of coupled spectral equations.Consideringthe third-order term in the drag force,the evaluation of the three-fold convolution should be demanded fornonlinear stochastic response analysis.To demonstrate this method,a numerical analysis is carrie     

海洋工程试验池中风场模拟

在考虑海洋工程装备在极端海况和运行海况下的载荷与受力,风载荷也是一个不可忽视的因素.目前物理模型试验仍是研究海洋工程结构物载荷与运动性能的重要手段,而深海结构物在水平漂移运动较大,如何在较大范围内得到满足试验要求的风场,是提高试验能力的重要问题.应用数值计算方法对大范围的风场模拟进行了分析,并进行了相应的物理实验,在此基础上对海洋工程试验的风场模拟提出了若干建议.     

Analysis of typhoon wind hazard in Shenzhen City by Monte-Carlo Simulation

As one of the most serious natural disasters,many typhoons affect southeastern China every year.Taking Shenzhen,a coastal city in southeast China as an example,we employed a Monte-Carlo simulation to generate a large number of virtual typhoons for wind hazard analysis.By analyzing 67-year historical typhoons data from 1949 to 2015 using the Best Track Dataset for Tropical Cyclones over the Western North Pacific recorded by the Shanghai Typhoon Institute,China Meteorological Administration(CMASTI),typhoon characteristic parameters were extracted and optimal statistical distributions established for the parameters in relation to Shenzhen.We employed the Monte-Carlo method to sample each distribution to generate the characteristic parameters of virtual typhoons.In addition,the Yah Meng(YM)wind field model was introduced,and the sensitivity of the YM model to several parameters discussed.Using the YM wind field model,extreme wind speeds were extracted from the virtual typhoons.The extreme wind speeds for different return periods were predicted and compared with the current structural code to provide improved wind load information for wind-resistant structural design.     

基于EOF分析中西太平洋金枪鱼围网渔场的海洋环境

根据近10 a ECMWF的数值预报资料,主要分析了中西太平洋金枪鱼围网渔场四季和全年的海表温度、海面风场、有效波高的空间分布,利用经验正交方法(Empirical Orthogonal Function, EOF)和经验模态分解(Empirical Mode Decomposition, EMD)分析了空间和时间变化特性。研究表明:海表温度、海面风场、有效波高的四季及全年时空分布有着显著的变化;海表温度的第一、第二、第三模态方差贡献率分别为62.59%、10.98%和6.7%,具有0.5 a、1 a和3 a的周期变化;海面风场的第一、第二、第三模态方差贡献率分别为40.29%、18.39%和9.36%,具有0.2~0.25 a、0.5 a和1 a的周期变化;有效波高的第一、第二、第三模态方差贡献率分别为44.17%、17.35%和10.96%,具有0.2~0.3 a、0.5~1 a和1 a的周期变化。     

A First Generation Stochastic Bioeconomic Analysis of Algal Bloom Control in a Coastal Lagoon (Sacca di Goro, Po River Delta)

Abstract. In this work we have developed a very simple stochastic mathematical model of Ulva spp. growth to quantitatively evaluate the economic costs of algal harvesting and the related benefits in terms of avoided'economic loss'of clam production due to an effective prevention of algal blooms and the consequent anoxic crises. Algal growth was simulated by means of a discrete time difference equation of Ulva biomass where the finite growth rate depends only upon water temperature. In order to explicitly include environmental variability, a seasonal autoregressive model calibrated on available data was used to simulate water temperature. Different harvesting scenarios were analysed in terms of the number of harvesting vessels employed and the threshold biomass of Ulva at which vessels start to operate. Costs of algal harvesting and disposal, as well as monetary damages resulting from the collapse of clam production as a consequence of algal blooms, were assessed by interviewing the managers of the Clam Fishermen's Union of Goro. A Monte Carlo approach was used to estimate the mean and total statistical distribution of costs and benefits of different harvesting strategies. Our analysis shows that the most cost-effective management policy is attained with 4–6 vessels operating at low algal density able to harvest as much Ulva as possible with intensive and short interventions at the beginning of the seasonal growth.     

上海海域站位观测风能资源分析

为探究上海海域风能资源的情况,按照《风电场风能资源评估方法》和《全国风能资源评价技术规定》中的相关方法,对东海浮标（深远海）和南槽灯船（近海）处2013—2018年实测的气象资料进行了分析比较。结果表明,东海浮标处累年平均风速为6.30 m/s,南槽灯船处累年平均风速为5.80 m/s,东海浮标处累年平均风速比南槽灯船处高8.6%;东海浮标处累年平均风功率密度为345.1 W/m²,南槽灯船处累年平均风功率密度为239.5 W/m²,东海浮标处累年平均风功率密度比南槽灯船处高44.1%;东海浮标处湍流强度的累年平均值为0.114,比南槽灯船处（0.125）低8.8%,对发电机组运行的影响低于南槽灯船处。本研究结果表明,东海浮标处的风能资源比南槽灯船处丰富,东海深远海的风能资源比近海丰富。