Artificial Reefs as Restoration Tools: A Case Study on the West Florida Shelf

Artificial reefs are one of a number of tools that should be considered by scientists and managers when planning coastal zone restoration and/or mitigation projects. In this article, the details of one project from the West Florida Shelf are presented. Two types of artificial reefs were used to mitigate pipeline construction impacts on natural hardbottom ledges in the eastern Gulf of Mexico. The project's primary objective was to avoid the paradigm of building artificial reefs as fish attraction devices, and to instead implement a design that would mimic, not augment, natural hardbottom conditions. Fish assemblage parameters (species richness and commercial fish abundances) were compared between the artificial habitats and natural hardbottom reference sites. Results indicate that species richness trends are similar among artificial and natural reefs, while certain commercial fish abundances are significantly higher on the artificial reefs. Recommendations for future restoration/mitigation projects using artificial reefs are discussed.     

Improving the State of Coastal Areas in the Asia-Pacific Region

Stresses impacting the coastal zone in the Asia-Pacific region are briefly reviewed under the headings of sustainable coastal activities, coastal ecosystem management, community/resource interactions, coastal resource economics and sustainability, coastal area planning, and integrated coastal policies. Recent contributions on mitigation of these stresses are introduced, with emphasis on the Coastal Zone Asia-Pacific Conference, held in Bangkok, May 2002, where various innovative approaches to research, education, information sharing, and coastal policies aiming at improving the state of the coastal areas were presented. These include the roles of community in integrated coastal management; tools and planning for management of coastal areas; education program and capacity building; and the establishments of national and regional frameworks for integrated coastal management. As appropriate information and its transfer are critical to these processes, an analysis is presented of the content of the database on coastal projects in the region, highlighting areas of research interests, funding sources, and achievements. Another database on coastal ecosystems, currently under development, is presented as an example of the type of resource that can be expected to help advance our knowledge and ability to improve the management of coastal areas. Overall, these tools should allow us, given the political will, to improve the state of coastal areas.     

One-dimensional modelling of the plankton ecosystem of the north-western Corsican coastal area in relation to meteorological constraints

In order to study the influence of wind mixing on the spring variability of the plankton production of the north western Corsican coastal area, a one-dimensional (1D), vertical, coupled hydrodynamic/biological model (ECOHYDROMV) is used. A hydrodynamic 1D model of the water column with a k–l turbulent closure is applied. The biological model comprises six state variables, representing the plankton ecosystem in the spring period: phytoplankton, copepods, nitrate, ammonium, particulate organic matter of phytoplanktonic origin and particulate organic matter of zooplanktonic origin. The system is influenced by turbulence (expressed by the vertical eddy diffusivity), temperature and irradiance. The model takes into account momentum and heat surface fluxes computed from meteorological data in order to simulate a typical spring atmospheric forcing for the considered area. Results show that primary production vertical structure is characterised by a subsurface maximum which deepens with time and is regulated by the opposite gradients of nitrate concentration and irradiance. Surface plankton productivity is mainly controlled by turbulent vertical transport of nutrients into the mixed layer. The short time scale variability of turbulent mixing generated by the wind appears to be responsible for the plurimodal shape of plankton blooms, observed in the considered area. Furthermore, the model is applied to the study of the spring evolution of the plankton communities off the bay of Calvi (Corsica) for the years 1986 and 1988. In order to initiate and validate the model, time series of hydrological, chemical and biological data have been used. The model reproduces accurately the spring evolution of the phytoplankton biomass measured in situ and illustrates that its strong variability in those years was in close relation to the variability of the wind intensity.     

珠机城际铁路公铁同层合建桥方案比选

珠机城际铁路金海特大桥跨磨刀门水道主通航孔跨径为3×340 m,采用公铁同层布置,结合桥址区建设条件,对桥型方案进行研究比选。从桥式上对比多塔斜拉桥方案与钢桁拱桥方案,由于设计基准风速大、台风频发、多主跨等因素,考虑经济性、施工难度及施工过程抗风稳定性,最终确定采用(58.5+116+3×340+116+58.5)m多塔斜拉桥方案。在此基础上,针对多塔斜拉桥,对桥塔中置和桥塔外包方案,从结构受力、施工、经济性、景观性等进行综合比选,最终推荐采用温度效应小及抗震性能好、施工工期短、经济性相当、景观效果好的桥塔中置方案。     

道岔区轮轨力转移与分配特性研究

道岔区复杂的轮轨接触状态决定了其轮轨力特性与一般线路相比存在较大的差异。利用空间轮轨接触几何关系理论和Hertz非线性弹性接触理论，研究道岔区车轮与同侧并列的2股钢轨同时接触的2点接触问题。依据2点接触时轮轨弹性压缩量计算每一接触点上的轮轨力，由此确定车辆侧向和直向通过时的轮轨2点接触范围以及轮轨力转移和分配特性。结果表明：2股钢轨上轮轨力转移和分配特性不仅与钢轨外形、轨顶高度和宽度有关，而且与车辆过岔方式有关；考虑轮轨2点接触后的计算方法，消除了单点接触轮轨力计算中轮轨接触点从一股钢轨转移到另一股钢轨上时引起的轮轨力突变，使得轮轨力变化更为平顺和真实。     

逆断层黏滑错动对跨断层隧道影响机制的模型试验研究

为指导隧道穿越活动断层时的抗错断设计,避免逆断层黏滑错动造成跨断层隧道结构的严重破坏,以棋盘石隧道为工程背 景,通过 1 ∶ 50 相似模型试验,研究逆断层黏滑错动所引起的山岭隧道破坏模式,分析隧道和地层变形过程及破坏特征,得到以下 结论: 1)逆断层错动在断层迹线附近地层形成剪切带,剪切带沿着断层线略微凸向试验装置上盘的弧线方向发展。2)断层错动对 试验装置上盘内隧道变形破坏的影响大于下盘,最大土压力和最大纵向应变主要分布在上盘隧道中; 土压力和纵向应变变化规律 相似,均随错动位移的增加而不断增加。3)隧道最终破坏为逆断层下的剪切破坏,局部伴随张拉破坏,剪切破坏主要表现为变形缝 两侧隧道衬砌脱落和纵向裂缝;断层错动对隧道影响区域主要集中在断层破碎带及附近2D(D 为隧道洞径)区域,尤其是试验装置 上盘部分,在跨断层隧道的设计阶段需引起足够重视。     

溢油对海洋生态系统的损害研究进展

海上溢油污染规模不断扩大,造成了严重的生态破坏和巨大的经济损失,研究者在溢油事故发生后利用实验研究溢油对各种海洋生物的影响,主要集中于对海洋生物种群的致死和致突变机理的研究。文章在对这些研究进行综述的基础上,对溢油海洋生物损害研究的实用性进行阐述,并提出了溢油实验室研究的发展方向和建立毒性数据库的必要性。     

青藏高原气候环境对混凝土强度和抗渗性的影响

为了研究青藏高原气候环境对混凝土性能的影响，在高原和平原地区完成相同配比混凝土的制备与养护工作，并结合强度、抗渗性、气孔结构、显微硬度以及扫描电镜与原子力显微镜分析等测试对比研究混凝土性能的差异，从宏观、细观和微观多个角度揭示高原气候条件对混凝土性能与内部结构带来的影响与作用机理。结果表明：高原地区制备且标准养护组混凝土的抗压强度与抗渗性都最优，其次是平原地区制备且标准养护组，高原地区制备且室外自然养护组性能最差；低气压导致混凝土拌合物含气量降低和工作性下降；高原标准养护下硬化混凝土含气量最低，平均孔径最小，而高原室外自然养护下硬化混凝土含气量最大，平均孔径最大；高原地区制备的混凝土，在标准养护条件下界面过渡区密实程度最高，结构均匀，其显微硬度最大，而室外自然养护条件下界面过渡区密实程度最差，微裂纹密布，结构粗糙，其显微硬度最小；而高原地区制备且室外自然养护条件下，混凝土气孔结构参数和界面过渡区微结构整体最差，以上原因的综合作用给混凝土力学和抗渗性带来极为不利的影响。总体来讲，青藏高原气候环境对混凝土性能的负面影响主要源于室外养护条件，而非制备过程。     

水平双向地震作用下钢桥墩损伤区域长度研究

钢板局部失稳是典型的钢桥墩地震破坏形式之一，因此在进行结构地震反应分析时需要考虑钢板局部变形对计算结果的影响。为了研究钢桥墩结构的地震损伤特征并为建立合理的杆系-板壳混合单元模型提供依据，以矩形截面钢桥墩为对象，采用板壳有限元模型和修正双曲面滞回本构模型分析了结构在水平双向反复荷载作用下的破坏过程，讨论了加载路径对桥墩承载力、延性以及极限状态下局部变形特性的影响；通过结构参数分析拟合了钢桥墩地震损伤区域长度预测公式；通过全板壳单元模型和杆系-板壳混合单元模型的桥墩弹塑性地震反应分析结果对比，验证了损伤区域长度预测公式的适用性。结果表明：钢桥墩在单方向上的承载能力和延性特性与荷载作用路径有关，沿正方形加载时结构的延性最小，沿斜方向加载时结构的承载力最小；荷载作用路径对钢桥墩极限状态下的损伤区域长度影响不明显；矩形截面钢桥墩地震损伤区域长度主要与截面宽度及横隔板间距有关，根据这2个参数建立的钢桥墩地震损伤域区域长度预测公式能够正确反映结构在水平双向地震作用下发生局部失稳的范围。该公式可为钢桥墩地震损伤范围预测以及合理混合单元模型的建立提供参考依据，但预测结果偏于保守，精度仍有待于进一步提高。     

多温多区铁路机械冷藏车的研发

我国铁路冷藏运输行业基础设施落后，运输损耗大，且难以调节，不能满足现在市场小批量、多品种的运输要求，遭到公路冷藏运输的巨大挑战，如果不能够尽快根据市场发展调整运输方式，很快就会被后者占领市场。针对这种情况，在原有单节冷藏车基础上，提出改装车厢结构，将其划分为多个温区，以实现同时存放不同种类、不同保存温度货物的冷藏运输，探讨了运用管理模式。多温多区铁路机械冷藏车降低了对运输货物量、货物种类的要求，拓宽了冷藏车的适应性，具有良好的市场竞争力。