港珠澳大桥西人工岛围护结构正式施工

5月15日,港珠澳大桥岛隧工程西人工岛首个钢圆筒顺利振沉,标志着人工岛围护结构正式开始施工。首个钢圆筒直径22 m,高40.5 m,振沉插入泥面21 m,为目前国内直径最大、高度最高的钢圆筒结构,也是世界上体量最大的钢圆筒结构。这也是全世界第一次采用8台液压振动锤联动振沉体系进行钢圆筒的振沉。     

膨润土泥浆改变砂性土振动密实特性的室内试验研究

钢圆筒结构具有施工工期短、经济、耐久性好、施工便捷等特点，目前已在粤港澳大湾区某工程和国内某跨江通道工程中应用。当地基中存在较硬的夹砂层时，钢圆筒在打设过程中会使砂层发生振密效应，造成砂层板结，给钢圆筒振沉带来了很大的困难，强行打设会导致钢圆筒结构产生破坏。因此有必要对夹砂层和砂层地基进行改性，改变砂层土体振动密实特性，使钢圆筒顺利振沉。通过室内膨润土改性砂样的试验研究发现：1）膨润土可以很好地降低砂土的抗剪强度，改性后的黏聚力c有一定的提升，但是内摩擦角φ降低较为明显。2）水土比对砂土抗剪强度的影响较小，膨润土掺量对泥浆改性砂土的抗剪强度有很大的影响。3）膨润土改性砂土选用的泥浆配合比，建议膨润土掺量为5%、水土比选择在8～20。     

全旋转起重船在大直径钢圆筒振沉施工中的应用

在大直径钢圆筒结构的护岸工程中,起重船规格型号的选用是施工准备阶段的一项重要工作,其直接影响到施工的安全、质量和进度。以某大型人工岛项目为例,对施工中所采用的全旋转起重船在选型过程、锚缆布设、驻位方式、施工振沉、艘班费用等方面进行详细描述。通过对比固定扒杆式起重船,总结出全旋转起重船在大直径钢圆筒振沉施工中的优势为:1)节省了放置锤组的船舶;2)起吊钢圆筒至振沉阶段不需要频繁移船,减少安全风险,提高作业效率;3)有利于钢圆筒定位、纠偏的操作。     

浅插法大直径钢圆筒在换砂振沉施工中的应用

大直径钢圆筒凭借其特有的优势被应用在大型人工岛护岸项目中.以某大型人工岛项目为例,针对浅插法大直径钢圆筒施工中遇到的一些实际问题进行方案比选.通过对振沉方法、纠偏方式、振沉顺序等技术方案的分析对比,总结出浅插法大直径钢圆筒在换砂基础中应用的主要工艺:点振法振沉工艺、起重船纠偏工艺和顺、跳打振沉顺序.     

大直径圆筒振动下沉施工新工艺

本文列举了大圆筒结构在国内的应用实例及施工工艺技术难题。应用液压振动锤组成功地振沉混凝土圆筒和钢结构圆筒，在国内外尚属首次，振动下沉这种新的施工工艺简便快速，解决了深埋式大圆筒施工工艺难题，为大圆筒结构的推广应用创造了条件。     

深中通道项目西人工岛首个钢圆筒顺利振沉

正4月29日,中交水运规划设计院有限公司(水规院)设计的深圳至中山跨江通道项目西人工岛首个钢圆筒顺利振沉,标志着深中通道项目进入了实质性的实体工程施工阶段。钢圆筒作为西人工岛围护结构,为人工岛内隧道干地施工提供重要保障。西人工岛轴线长度为625 m,横向最大宽度为456 m,岛体面积13.7万m~2,岛壁结构长度为1 622 m。西人工岛整体呈菱形,57个钢圆筒和116个副格勾勒出"海上风筝"的素描画。钢圆筒直径28 m,高35~39.5 m,筒质量653 t。深中通道西人工岛采用12台进口APE600型液压振动锤联动振沉方案,以保证钢圆筒振沉顺利。     

大直径钢筋混凝土圆筒振沉试验结果分析

简要介绍了大直径钢筋混凝土圆筒振沉试验概况和试验结果分析。     

深中通道西人工岛钢圆筒成岛应用及稳定性分析

深中通道西人工岛采用大直径钢圆筒插入海床围闭岛体的快速成岛工艺.目前,采用钢圆筒快速成岛的案例相对较少,对钢圆筒施工期倾斜及简体稳定性的研究尚待进一步深化.文中以深中通道西人工岛为例,针对钢圆筒振沉直至人工岛陆域形成各施工工况,就简体在岛内外荷载综合作用下发生倾斜超限的成因进行分析,得出具体成因与地质条件及施工期简体内...     

港珠澳大桥西人工岛钢圆筒及岛内回填砂成岛技术

港珠澳大桥西人工岛钢圆筒及副格围护结构振沉完成后，为确保其整体稳定性，采用定点、接力、分层抛填的方案对钢圆筒及副格内回填砂施工，有效控制了钢圆筒围护结构在回填砂施工期间的结构稳定性，防止了不利工况的出现。人工岛围闭前，采取设置龙口直接抛填以及泵送等方式进行水下回填；人工岛围闭后，采取水上抛填加陆上倒运的方案快速实现了人工岛陆域形成，为外海人工岛快速成岛积累了经验。     

大直径沉管的东营港^#2内港池口门工程中的应用

大圆筒结构由于具有材料用量省，结构尺寸大，受力条件好的优点，在港口工程中被推广应用，目前，已有的工程实例以有基床的大圆筒结构居多，沉入式的沉管结构工程实例极少。文章通过在潮间带就地边预制边下沉的大直径沉管结构的工程实例，介绍结构设计应注意的问题和施工工艺措施。     

Coastal Erosion in Ghana: Causes,Policies, and Management

Coastal erosion is a serious problem that affects the safety and livelihoods of many coastal dwellers along Ghana's coast. Despite the fact that coastal erosion is a natural phenomenon, erosion trends have been largely aggravated by human-induced factors. This study analyzed shoreline change rates for three neighbouring coastal communities in the Central region of Ghana; Elmina, Cape Coast and Moree. Two epochs were analyzed, 1974–2012 (medium-term) and 2005–2012 (short-term), using ArcGIS and Digital Shoreline Analysis System. Overall, the entire study area recorded average shoreline change rates of ?1.24 myear^?1 and ?0.85 myear^?1 in the medium-term and short-term period respectively. Less consolidated shoreline segments recorded higher erosion rates in both periods while cliffs and rocky segments experienced very little erosion or high stability. Because shorelines undergoing chronic erosion do not fully recover after short-term erosion events such as storms, facilities located close to such shorelines are threatened. Taking a proactive approach to coastal erosion management, such as coastal sand mining prevention, inter-sectoral land use management and adopting a construction setback approach may be prudent for the long-term management of the coast since this recognizes future shoreline changes and safeguards coastal landscape for other uses.     

Sediment geochemistry and mineralogy in Milos bay, SW Kyklades, Aegean Sea, Greece

This work aims at studying the geochemistry and mineralogy of Milos bay surface sediments. The bay forms an enclosed marine area, supplied totally by volcanic formations. Totally 16 samples were subjected to sedimentological (grain size), mineralogical (microscope examination and X-ray diffraction of the bulk sample and the pelitic fraction), and geochemical analyses (X-ray fluorescence in the pelitic fraction). Also the carbonate content was determined. Sediments were sandy with a high carbonate content (14–58%). The dominant minerals recognized in the pelitic fraction were smectite, kaolinite and illite, followed by chlorite, quartz, calcite, Mg-calcite and feldspars. In general, element concentrations appeared to be within the normal range, except Pb and Zn, which exhibited relatively high values. The Index of Geoaccumulation I_geo was computed, in order to investigate a possible enrichment of the surface sediments in metals. The analysis revealed again high values of I_geo class for both Pb and Zn. A careful study of the area, in relation to the quality of the catchment basins petrology, lead to a non-anthropogenic origin of these high concentrations. The enrichment of the surface sediments in Pb and Zn is attributed to the weathering of several mineral deposits, pyroclastic rocks and lavas, covering almost all Milos vicinity. A study of the geochemical data correlation coefficient matrix revealed three major groups of elements: (i) the elements of detrital origin represented by Si, Al, K and a part of the metals; (ii) the carbonates group; and (iii) a Fe–Mn oxyhydroxides–oxides group, which attracts a part of Pb, Cr and Ni.     

广东海事局:主动作为靠前服务助力粤港澳大湾区建设

2020年5月8日,《广东省人民政府关于复制推广中国(广东)自由贸易试验区第六批改革创新经验的通知》中,广东海事局实施船舶证书文书"一次通办",以及建立一个核心(以智慧海事应用为核心)、三种方式(政务窗口定点查、电子巡航标线查、现场执法随机抽查)、多种工具(报告服务网、船舶动态管理系统等)"点线面"结合的船舶进出港报告...     

Synoptic transects on the distribution of trace elements (Hg,Pb, Cd,Cu, Ni,Zn, Co,Mn, Fe,and Al) in surface waters of the Northern- and Southern East Atlantic

Surface seawater samples were taken in the framework of the GEOTRACES program on “POLARSTERN” expedition ANT XXIII/1 in the Eastern Atlantic in 2005 to study the distribution of the trace elements Hg (mercury), Pb (lead), Cd (cadmium), Cu (copper), Ni (nickel), Zn (zinc), Co (cobalt), Mn (manganese), Fe (iron), and Al (aluminium). With the exception of Hg, results were compared to earlier datasets from 1989 to 1990. The particulate fraction averaged over the transect was calculated to be 49% for Cd, 23% for Mn and 50% for Fe indicating a release of these TEI's (trace elements and their isotopes) from a leachable SPM fraction in the stored and acidified samples.Total Pb concentrations ranged between 5 and 20 pmol kg^? 1 in 2005 with highest values in the ITCZ (intertropical convergence zone). In 1989 Pb concentrations were twice as high in the region of the ITCZ, while by a factor of 10–15 higher values were obtained in the North Atlantic.Total Cd and Co are dominated, by different seasonal upwelling regimes (Equatorial upwelling, Guinea Dome, Angola Dome).Total Cu, Ni, Fe, Mn and Al show nearly identical concentrations in 1990 and 2005. For total manganese and aluminium strong maxima (3–4 nmol kg^? 1 and 55 nmol kg^? 1 respectively) are observed between 23°N and 0°, while the Fe maximum (6–9 nmol kg^? 1) is located at 7°N. Total Hg concentrations ranged between 0.5 and 4.5 pmol kg^? 1.     

Particle flux, and composition of sedimenting matter, in the Greenland Sea

Vertical flux of particulate material was recorded with moored sediment traps during 1988/1989 in the Greenland Sea at 72°N, 10°W. This region exhibits pronounced seasonal variability in ice cover. Annual fluxes at 500 m water depth were 22. 79, 8.55, 2.39, 3.81 and 0.51 g m⁻² for total flux (dry weight), carbonate particulate biogenic silicate, particulate organic carbon and nitrogen, respectively. Fluxes increased in April, maximum rates of all compounds occurred in May–June, and consistently high total flux rates of around 100 mg m⁻²d⁻¹ prevailed the summer. The increasing flux of biogenic particles measured in April is indicative of an early onset of algal growth in spring. Small pennate diatoms dominated in the trap collections during April, and were still numerous during the high flux period when Thalassiosira species were the most abundant diatoms. During May–June, up to 22% of the Thalassiosira cells collected were viable-looking cells. The faecal pellet flux increased after the May–June event. Therefore we conclude that the diatoms settled as phytodetritus, most likely in rapidly sinking aggregates. From seasonal nutrient profiles it is concluded that diatoms contribute 25% to new production during spring and 50% on an annual basis. More than 50% of newly produced silicate particles are dissolved above the 500 m horizon. High new production during spring does not lead to a pronounced sedimentation pulse of organic matter during spring but elevated vertical export is observed during the entire growth period.     

Economic value of fish,wildlife, and recreation in Michigan's coastal wetlands

On the basis of annual expenditures by recreational participants and standard values of recreation days, as well as estimated sport and commercial harvests, the gross annual return from Michigan's 105,855 acres of coastal wetlands has been estimated. Analysis of fish, wildlife, and recreational values revealed that in 1977 these wetland areas generated an economic value of $489.69 per wetland acre, for a direct annual gross of $51.8 million. Specifically, these average return values per wetland acre/year, in descending order, are sport fishing ($286), nonconsumptive recreation ($138.24), waterfowl hunting ($31.23), trapping of furbearers ($30.44), and commercial fishing ($3.78). These gross annual return values were calculated in an effort to sensitize the general public to the diversity and possible magnitude of selected wetland functions.     

江苏如东人工岛建设对周边水动力及泥沙冲淤的影响

在南黄海辐射沙洲这样一个水动力和泥沙环境都相当复杂的区域建设浅水人工岛,不仅要考虑人工岛本身的稳定型问题,还要深入地认识浅水人工岛建设引起的流场和泥沙冲淤是否造成目前潮流动力场和"水道—沙洲"系统格局的较大变异、自然演变的趋势性过程是否因人工岛建设而加速或逆转。通过整体潮流泥沙物理模型研究了西太阳沙人工岛工程对滩槽演变趋势的影响和工程区滩冲槽淤的短期波动,探讨了如东人工岛工程建设后,岛周围水动力和泥砂冲淤的变化规律,提出了相应的防冲措施。结果表明,拟建人工岛工程建设引起的水流动力变化主要在西太阳沙附近的浅水区,并局限在1.5倍人工岛直径范围内,对邻近水道深槽区的潮流动力没有影响。人工岛工程没有改变西太阳沙周边各水道潮流动力场格局,没有引致水道间潮流动力此消彼长的变化、未改变控制西太阳沙"水道-沙洲"系统演变的动力泥沙环境,西太阳沙核心部位的稳定主要取决于西太阳沙北侧潮流动力增强的自然演变过程。就人工岛建设而言,东北岛壁前沿有效的防冲护底措施对沙洲核心部位稳定和减少北水道深槽淤积泥沙来源均有积极意义。     

Late summer stratification, internal waves, and turbulence in the Yellow Sea

Microstructure profiling measurements at two locations in the Yellow Sea (a deeper central basin and a local shelf break) were analyzed focusing on tidal and internal-wave induced turbulence near the bottom and in the pycnocline. A classical three-layer density structure consisting of weakly stratified surface and bottom boundary layers and a narrow sharp pycnocline is developed by the end of warm season. Turbulence in the surface layer was not influenced by the tidal forcing but by the diurnal cycle of buoyancy flux and wind forcing at the sea surface. The enhanced dissipation and diffusivity generated by the shear stress at the seafloor was found in the water interior at heights 10–15 m above the bottom with a phase shift of ~ 5–6 m/h. No internal waves, turbulence, or mixing were detected in the pycnocline in the central basin, in contrast to the pycnocline near the local shelf break wherein internal waves of various frequencies were observed all the time. The thickness of the surface layer near the local shelf break slightly exceeded that of the bottom layer (20 vs. 18 m). A 5–6 m high vertical displacement of the pycnocline, which emerged during the low tide, was arguably caused by the passage of an internal soliton of elevation. During this episode, the gradient Richardson number decreased below 0.25 due to enhanced vertical shear, leading to local generation of turbulence with dissipation rates exceeding the background level by an order of magnitude.     

Facts,Fictions, and Failures of Integrated Coastal Zone Management in Europe

Nearly 40 years on since its first tentative steps in North America, this article considers whether Integrated Zone Coastal Management (ICZM) in Europe has grown to maturity as a form of governance. The article summarizes the findings of recent research concerning the levels of implementation of coastal management in Europe, with particular reference to the UK experience. A research framework is used to identify the different motivations behind the social actor groups involved in coastal management. The application of this framework reveals four major findings about gaps in implementation: (1) the complexity of responsibilities at the coast continues to prevent agencies from taking a “joined-up” approach; (2) a policy vacuum is constraining implementation from national to local scales; (3) informational obstacles are significant in preventing co-ordination between science and policymakers, and between different sectors; (4) a democratic deficit is preventing implementation in the working practices of coastal stakeholders, with little opportunity in decision making for public comment or local accountability, especially offshore. The article also explores different conceptualizations of the role of coastal management and planning held across Europe, providing an analysis using the Strategic Management literature and the experience of the EU Demonstration Programme on Integrated Coastal Zone Management (1996–1999). Recent arrangements, with the availability of priming funds from the European Commission and emphasis on “pilot” and “demonstration” methods, have tended to encourage a project-based approach to ICZM that may fail to realize long-term objectives. The article seeks to present an analysis of the behaviors of scientists, academics, policymakers, and practitioners, and will be of interest to all those seeking to establish ICZM within the wider system of governance, as supported by the Commission of the European Community (2000) Communication on ICZM (COM 547). Some technical solutions are also offered from the UK experience that will be of use to coastal project officers working at national and regional levels.