固定式海洋平台结构风险设计方法综述     

李晓冬  唐文勇 《海洋工程》2017,35(1):147-156

海洋平台的结构设计中主要考虑海洋环境和工作荷载作用,但近年来事故荷载的影响日益引起设计者关注。在此背景下,以固定式导管架平台结构为目标,综述当前针对事故荷载的风险设计方法的应用现状。首先论述在事故极限状态设计中应用风险分析的必要性;随后综述通用规范,如NORSOK、DNV、API等规范系列中对风险分析方法的使用现状,包括风险决策的不同层次、安全标准的各类形式,重在分析各类规范相关规定的异同,探讨各类方法的适用性;最后结合我国现状,论述若针对事故荷载编制基于风险方法的设计规范,目前尚存的问题,以及解决途径。  相似文献   

150ka以来内蒙古河套古大湖沉积物粒度记录的湖泊水位变化   总被引：1，自引：0，他引：1  

杨星辰  叶培盛  蔡茂堂  常鹏渊  游报捷  李成路  叶梦旎  蔡惠慧 《地质通报》2017,36(6):1043-1050

基于内蒙古河套盆地山前兵房沟湖相层剖面沉积物的粒度记录,结合~(14)C和光释光年代学测试,对比分析沉积物粒度敏感粒级及频率曲线特征,反演了河套古大湖150ka以来的湖泊水位变化。研究结果表明,河套古大湖水位变化经历了4个阶段:(1)初始形成阶段(150~130ka),河套古大湖处于浅湖环境,沉积物粒度由粗变细,湖泊处于水位上升期;(2)发展阶段(130~54ka),早期湖水面较高,处于深水环境,晚期沉积物粒度逐渐变粗,湖泊水位有所下降;(3)萎缩阶段(54~18ka),湖泊水位快速下降,细粒沉积物含量减少,中粗粒沉积物含量增大,湖泊水位迅速下降;(4)消亡阶段(18ka至今),由于山前活动断裂影响,阴山快速隆升,湖泊急剧萎缩,湖相层顶部被山间冲洪积物覆盖。控制河套古大湖湖泊水位变化的主要因素是构造运动和气候环境突变。  相似文献   

Optical dating and soil micromorphology at MacCauley's Beach,New South Wales,Australia   总被引：1，自引：0，他引：1       下载免费PDF全文

Nathan R. Jankowski  Zenobia Jacobs  Paul Goldberg 《地球表面变化过程与地形》2015,40(2):229-242

The ability to position landscapes in a context of time and space is a particular goal of Quaternary science research. The lack of context for dating samples published previously for MacCauley's Beach, an important site for the reconstruction of Australian sea levels, warranted a re‐evaluation of both the site stratigraphy and chronology. In this study, we combined optically stimulated luminescence (OSL) dating of sedimentary quartz grains and soil micromorphology of the same samples to improve our understanding of the depositional history and chronology of the sediments. This combination allowed the contextualization of samples not only in time and space, but also in terms of their depositional histories. The latter is important in OSL dating, where pre‐, syn‐ and post‐depositional processes can all influence the accuracy and precision of the final age estimates. The sediment profile at MacCauley's Beach is made up of three major units. The basal mottled mud layer has undergone extensive pedogenesis since deposition, and only a minimum age of 14.7 ± 2.7 ka could be calculated. The overlying grey mud, with OSL ages from the bottom and top of the unit of 10.0 ± 0.7 and 7.7 ± 0.5 ka, respectively, shows evidence of soil structure collapse. This unit correspond to the onset of the mid‐Holocene sea‐level high stand for this region. The overlying sand layer was first deposited at 7.5 ± 0.4 ka, with deposition continuing beyond 6.6 ± 0.4 ka. Not only does the chronology presented constrain the timing of deposition (and the extent of post‐depositional processes) at MacCauley's Beach, but the methodological approach used here can be applied to any site to aid in the interpretation of formation processes and assess their influence on OSL age determination. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

A meta‐analysis of reef island response to environmental change on the Great Barrier Reef          下载免费PDF全文

Sarah M. Hamylton  Marji Puotinen 《地球表面变化过程与地形》2015,40(8):1006-1016

Reef islands on the Great Barrier Reef are influenced by a range of environmental factors. A meta‐analysis of 103 islands is presented to express variation in island size (area and volume) as a function of latitudinal and cross shelf gradients in regional oceanographic factors (exposure to incident waves, tidal range and tropical cyclone frequency) and local physical factors (position on the shelf, area, length and depth of supporting reef platform, vegetative cover). Models performed well for unvegetated sandcays (R² = 0.89), vegetated sandcays (R² = 0·72) and low wooded islands (R² = 0.78), with a moderate level of variation explained when all islands were simultaneously regressed (R² = 0.58). Future island dynamics were simulated for anticipated changes in cyclone regime, wave activity and sea level. For 38 islands mapped on the 1973 Royal Society and Universities of Queensland Expedition to the Northern Great Barrier Reef, change over the same 22 year period (1973–1995) was determined and the relative magnitude of observed and modelled changes was compared and found to be consistent through rank correlation analysis (Γ = 0.84 for unvegetated sandcays, Γ = 0.81 for vegetated sandcays). Simulations of island area or volume change from 2000 to 2100 indicated that under a 30% decrease in tropical cyclone activity, unvegetated sandcays continue to accrete at a lower rate, whereas all island types erode under a 38% increase in tropical cyclone activity. Vegetated sandcays initially accrete at higher levels of cyclone activity, entering an erosive state with a 60% increase in activity. Low wooded islands are unresponsive to environmental changes modelled. A sensitivity analysis of vegetated and unvegetated sandcays indicated that the presence of vegetation increases the tropical cyclone activity threshold at which islands begin to erode. Greatest sedimentary losses occur within the central band of high cyclone activity between Cooktown and Mackay. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Prograded foredunes of Western Australia's macro‐tidal coast – implications for Holocene sea‐level change and high‐energy wave impacts          下载免费PDF全文

Max Engel  Simon Matthias May  Anja Scheffers  Peter Squire  Anna Pint  Dieter Kelletat  Helmut Brückner 《地球表面变化过程与地形》2015,40(6):726-740

The Holocene evolution of the Canning Coast of Western Australia has largely been overlooked so far mainly due to its remoteness and low population density. We report on new data from a sequence of foredunes inside the macro‐tidal Admiral Bay, 110 km southwest of Broome. Based on sediment cores, differential global positioning system (dGPS)‐based elevation transects, and stratigraphical analyses on outcrops of the relict foredunes, we aim at reconstructing Holocene coastal changes and relative sea levels (RSLs), as well as identifying and dating imprints of extreme‐wave events. Sedimentary analyses comprise the documentation of bedding structures, foraminiferal content and macrofaunal remains, grain size distribution, and organic matter. The chronological framework is based on 26 carbon‐14 accelerator mass spectrometry (¹⁴C‐AMS) datings. Marine flooding of the pre‐Holocene surface landward of the 2.5 km‐wide foredune barriers occurred 7400–7200 cal bp , when mangroves colonized the area. After only 200–400 years, a high‐energy inter‐tidal environment established and prevailed until c. 4000 cal bp , before turning into the present supralittoral mudflat. During that time, coastal regression led to beach progradation and the formation of aligned foredunes. Drivers of progradation were a stable RSL or gradual RSL fall after the mid‐Holocene and a positive sand budget. The foredunes overlie upper beach deposits located up to >2 m above the present upper beach level and provide evidence for a higher mid‐Holocene RSL. Discontinuous layers of coarse shells and sand are intercalated in the foredunes, indicating massive coastal flooding events. One such layer was traced over three dune ridges and dated to c. 1700–1550 cal bp . However, it seems that most tropical cyclones induce net erosion rather than deposition at aligned foredunes and thus, they are only suitable for reconstructing temporal variability if erosional features or sedimentation reliably tied to these events can be identified and dated accurately. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

城镇化水平与制造业空间分布——基于中国省级面板数据的实证研究   总被引：5，自引：2，他引：3  

陈曦  席强敏  李国平 《地理科学》2015,35(3):259-267

基于2001~2011 年中国省区面板数据,聚焦于城镇化水平与中国制造业空间分布。研究表明,城镇化水平是中国制造业空间分布的重要影响因素之一,两者之间存在倒"U"型关系,以中国各省区制造业产值占全国制造业总产值的份额反映中国制造业的空间分布,当城镇化水平超过36.26%后,城镇化水平的进一步提高不再推动制造业份额上升,反而会导致其下降。进一步研究发现,劳动密集型、资本密集型和技术密集型3 种类型制造业在空间分布、份额变化和与城镇化水平的相关性上均存在一定程度的差异性,并印证了制造业内部存在由劳动密集型、资本密集型向技术密集型转型升级的基本规律。此外,交通设施水平、区位条件等因素也会对中国制造业空间分布产生影响。  相似文献   

金融空间联系及K-means聚类中心等级识别研究——以长三角为例     

杨志民  化祥雨  叶娅芬  邵元海 《地理科学》2015,35(2):144-150

以2001年、2006年、2011年长三角城市金融机构人民币存款、贷款额数为样本,构建金融空间联系模型,定量分析长三角城市金融空间联系分异特征。在此基础上构建K-means金融中心等级识别模型,识别长三角城市金融中心等级。研究表明：① 2001-2011年长三角城市金融“质量”空间趋势较为稳定,总体呈现东部高于西部,中部高于南、北部的倒U形分布。② 金融空间联系最大引力线联结格局较为稳定。③ 金融空间联系网络结构格局变化显著,主要从简单的“折线型”空间结构逐渐发展成简单的、复杂的“网络型”空间结构。④ 长三角金融城市中心等级空间分布格局稳定,以上海市金融中心最为突出。  相似文献   

珠江三角洲地区未来海平面上升及风暴潮增水的耕地损失预测   总被引：1，自引：0，他引：1  

康蕾  马丽  刘毅 《地理学报》2015,70(9):1375-1389

珠江三角洲地区是中国海岸带中风暴潮灾害最集中的区域之一。在全球气候变化和海平面上升的影响下,风暴潮灾害将对该地区农业生产造成巨大的损失。在借鉴相关经验与研究的基础上,建立风暴潮增水灾害耕地产量损失评估模型,选择广东省珠江三角洲地区为研究区域,以该地区的DEM、土地利用等数据为基础,通过实地调研获取当地的作物种植结构、轮作方式、作物单产、不同淹没高度下不同作物的损失率等数据资料,基于未来海平面上升及风暴潮增水的不同时间情景,估算并分析了2030、2050及2100年珠三角地区耕地受灾范围的空间分布特征及产量损失变化情况。结果表明：受气候变化的影响,未来珠三角地区风暴潮影响下的耕地淹没面积比重不断上升,其中阳江、佛山和东莞等地耕地淹没面积从2030年到2100年增加较为明显,广州和珠海的耕地淹没面积增加幅度则较为缓和。从耕地淹没造成的农业产量损失来看,蔬菜、稻谷和花生等主要作物的损失产量比重呈现增加趋势,且蔬菜的增幅最大,其次是稻谷。其中广州、江门、阳江等地稻谷、花生、蔬菜的损失产量比重均表现为持续上升。  相似文献   

基于镇域尺度的江苏省人口分布空间格局演变   总被引：4，自引：2，他引：2  

车冰清  仇方道 《地理科学》2015,35(11):1381-1387

基于2000年、2010年人口普查乡镇（街道）数据,运用探索性空间数据分析、半变异函数等方法,分析江苏省人口分布的时空分异特征,并揭示其空间演化机理。结果表明：① 江苏省人口分布呈现较大的空间差异,全省层面上呈现南北人口密度高于中部的“凹”字型结构,城乡层面上呈现街道人口密度高于乡镇的“城乡二元”结构,以及沿江地区明显的“核心边缘”结构;② 研究期内江苏省人口分布的空间不均衡性和集聚性呈增强之势,长江以北镇域的人口密度大多降低而以南普遍增加,苏锡常、南京、徐州三大都市圈的人口集聚能力进一步提升,沿江地区成为全省规模最大的高密度人口连绵区;③ 空间关联作用是引起江苏省人口分布格局变化的空间机理,而政策、区位、经济与自然环境等因素是造成江苏人口格局变化的主要动力。  相似文献   

鄂尔多斯市2005-2014年地下水位变化     

郑玉峰  王占义  方彪  何晨  李路建  李春筱 《中国沙漠》2015,35(4):1036-1040

鄂尔多斯市地处半干旱区,水资源缺乏,监测地下水位的变化对于地区生态和经济发展具有重要意义。本研究利用鄂尔多斯市6个地下水位监测井2005-2014年的监测资料,分析了该地区地下水位变化特征。结果显示:(1)本地区地下水位2005-2006年有所下降,2007-2010年逐年抬升,2011年受严重干旱影响,地下水位为近10年来最低值,从2012年开始至2014年,以每年0.14 m的幅度抬升,2014年为近10年最高值,地下水位的年际变化主要与煤炭开采和经济发展有关。(2)地下水位的年内季节变化明显,与降雨量、蒸发量和农业灌溉用水的相关性较高。3-7月,水位持续下降,7月地下水位为年内最低点;8-10月,水位逐步回升;11月至次年2月水位总体呈略微抬升状态,次年2月为年内最高值。  相似文献