Structural Safety Assessment for FLNG-LNGC System During Offloading Operation Scenario     

HU Zhi-qiang  ZHANG Dong-wei  ZHAO Dong-y  CHEN Gang 《海洋工程》2017,31(2):192-201

The crashworthiness of the cargo containment systems (CCSs) of a floating liquid natural gas (FLNG) and the side structures in side-by-side offloading operations scenario are studied in this paper. An FLNG vessel is exposed to potential threats from collisions with a liquid natural gas carrier (LNGC) during the offloading operations, which has been confirmed by a model test of FLNG-LNGC side-by-side offloading operations. A nonlinear finite element code LS-DYNA is used to simulate the collision scenarios during the offloading operations. Finite element models of an FLNG vessel and an LNGC are established for the purpose of this study, including a detailed LNG cargo containment system in the FLNG side model. Based on the parameters obtained from the model test and potential dangerous accidents, typical collision scenarios are defined to conduct a comprehensive study. To evaluate the safety of the FLNG vessel, a limit state is proposed based on the structural responses of the LNG CCS. The different characteristics of the structural responses for the primary structural components, energy dissipation and collision forces are obtained for various scenarios. Deformation of the inner hull is found to have a great effect on the responses of the LNG CCS, with approximately 160 mm deformation corresponding to the limit state. Densely arranged web frames can absorb over 35% of the collision energy and be proved to greatly enhance the crashwo-rthiness of the FLNG side structures.  相似文献   

Experimental prediction of the noncontact jet Trencher’s excavation depth in clay     

Shusen Zhang  Chun Wang  Tong Ge 《Marine Georesources & Geotechnology》2017,35(2):300-304

Trenching depth calculation of traveling jet is a very important field in both pipeline burying and dredging engineering. The trenching ability of a noncontact control flow jet trencher was predicted by experimental method according to the geometry similarity. In the test, the jet pressure, the shear strength of clay, and the translational speed of nozzle were the same with the design parameters, while the nozzle was a reduced scale model. The trenching depth was found about seven to nine times of the nozzle’s diameter. The width of the trench was about four times of the nozzle’s diameter. Based on the test results the noncontact jet trencher was produced and succeeded in practical usage.  相似文献   

Tension and Drag Forces of Flexible Risers Undergoing Vortex-Induced Vibration     

SONG Lei-jian  FU Shi-xiao  LI Man  GAO Yun  MA Lei-xin 《海洋工程》2017,31(1):1-10

This paper presents the results of an experimental investigation on the variation in the tension and the distribution of drag force coefficients along flexible risers under vortex-induced vibration (VIV) in a uniform flow for Reynolds numbers (Re) up to 2.2×10⁵. The results show that the mean tension is proportional to the square of the incoming current speed, and the tension coefficient of a flexible riser undergoing VIV can be up to 12. The mean drag force is uniformly and symmetrically distributed along the axes of the risers undergoing VIV. The corresponding drag coefficient can vary between 1.6 and 2.4 but is not a constant value of 1.2, as it is for a fixed cylinder in the absence of VIV. These experimental results are used to develop a new empirical prediction model to estimate the drag force coefficient for flexible risers undergoing VIV for Reynolds number on the order of 10⁵, which accounts for the effects of the incoming current speed, the VIV dominant modal number and the frequency.  相似文献   

深海布放缆不同材料属性下应力波自由传播频率特性影响研究     

吴丞昊  杨建民  田新亮  胡智焕  彭涛 《海洋工程》2017,35(5):12-22

在频域对深海布放缆系统内应力波自由传播特性进行了分析。在布放缆数学建模时使用了哈密顿原理,并在建模时考虑布放缆的曲率。计算过程中保留了缆绳曲率与其弧长坐标之间的非线性关系,并最后得到了其上传播的应力纵波与应力横波的特性。通过计算得到布放缆属性和缆绳内竖直张力等参数对缆绳内自由传播频率特性的影响曲线。结果表明,这些因素对自由传播应力波的频率关系、色散关系、相速度与群速度影响显著。对于应力纵波,整个频域可被两个截止频率与一个行波截止频率分成四个区域。除了通频带之外,在低频时亦存在抑止带和行波抑止带。应力纵波仅能在通频带中以行波形式传播,而应力横波则可以在所有频率范围内以行波形式传播。  相似文献   

The interrelationship between travel behavior and life choices in adapting to flood disasters     

Qing-Chang Lu  Junyi Zhang  A. B. M. Sertajur Rahman 《Natural Hazards》2017,85(2):1005-1022

Disasters resulting from climate change are shown to be important determinants of people’s life choice decisions. In the literature, travel behavior choice and life choices are usually addressed separately under disasters such as flood and cyclone. However, travel behavior may be interdependent with other life choices, jointly shaping people’s adaptation decisions. To this end, the paper advances the literature by exploring the interrelationship between changes in travel behavior and job and residential location under flood disasters, while separating coastal and inland observations. For this purpose, a stated preference survey was conducted in 14 cities of Bangladesh in early 2013. An analysis approach based on structural equation modeling was developed to investigate the correlations between travel behavior change and job and residential location changes. Model estimation results suggest that flood impacts have significant influences on inland people’s life choices, while coastal people’s life choices are mainly affected by flood adaptation responses and attitudes. Significant correlations between travel behavior change and job and residential location changes are found for both observations. Moreover, both coastal and inland people tend not to change residential locations if changes in job location and travel behavior are made. Inland people may not change travel behavior if their job and/or residential locations are changed, but coastal people’s job and residential location changes are associated with changes in travel behavior. Travel behavior change is found to have more of an effect on residential location change than job location change in both regions. These findings conclude that the two-way relationship between travel behavior and life choices should be taken into account in future analyses, and thus adaptation policies to climate change disasters could be better linked with people’s behavioral responses.  相似文献   

Historical tsunami records and potential tsunami scenarios near Haikou coastal region     

Xi Zhao  Yunpeng Jiang  Zhiyuan Ren  Hua Liu 《Natural Hazards》2017,89(2):625-645

Historical tsunami records in the South China Sea are collected and analyzed in this paper. There have been about 54 tsunamis in the South China Sea since 1076. The impacts of the transoceanic tsunamis on the southeast coast of China are weak. However, the regional tsunamis in the South China Sea bring varying degrees of influence to the south coast of China, which occurred about 18 times. By the analysis of the potential tsunami sources in the South China Sea, numerical simulations of tsunami induced in the Manila Trench are carried out. It is found that the tsunami wave height is small near Haikou if the general earthquake tsunami occurred. But the tsunami wave height is large when a giant earthquake of M9.3 occurred. If this extreme situation arises, the impacts to the coast of Haikou will be serious.  相似文献   

江苏如东西太阳沙及烂沙洋海域潮流泥沙数值模拟   总被引：10，自引：0，他引：10  

李孟国  时钟 《海洋通报》2005,24(6):9-16

基于不规则三角形网格有限差分法并考虑波浪及其破碎作用,建立了平面二维潮流场和泥沙场数学模型.该模型对有望建设成深水码头和深水航道的江苏如东西太阳沙和烂沙洋海域的潮流场和泥沙场进行了细化数值模拟.数值模拟结果表明：（1）本海区潮流基本上是顺深槽流动的往复流,潮流流速大,烂沙洋北水道和西太阳沙附近大潮涨落潮最大流速分别在2 m/s和1 m/s以上;（2）本海区的潮平均水体含沙量在0.5 kg/m^3以下,落潮含沙量大于涨潮含沙量;（3）小浪对水体含沙量影响很小,大浪作用下水体含沙量明显增加.  相似文献   

栗西沟尾矿坝地震响应及液化分析     

吴远亮  仵彦卿  郭振世 《煤田地质与勘探》2006,34(2):45-47

采用不排水有效应力法,利用Geo-slope软件,对金堆城栗西沟尾矿坝进行了地震响应的综合分析与液化计算。结果显示: a .栗西沟尾矿坝在静态条件下是稳定的; b .在7度地震条件下,尾矿坝的加速度反应较小,其放大倍数为2.204; c .栗西沟尾矿坝内动剪应力和动孔压绝大部分是随着地震历时的增加而逐渐增大; d .坝内孔压比都较小,抗液化安全系数较大,但局部液化区的存在,仍可能影响到整个坝体的安全性,应在液化区采取加固措施。   相似文献   

Field investigations and laboratory simulation of clogging in Lixi tailings dam of Jinduicheng,China     

Jun Wu  Yanqing Wu  Jian Lu  Leonora Lee 《Environmental Geology》2007,53(2):387-397

Clogging is one of the most important factors affecting the stability of the tailings dams. Firstly, this work investigates the clogging materials of Lixi tailings dam using ICP-AES, X-ray powder diffraction (XRD) and SEM analysis methods. The ICP-AES results indicate that Fe is the dominant element in the clogging materials. The iron contents of clogging samples collected from 2# radial-well pipe and the access hole of the starter dam are 54.35 and 40.24%, respectively. XRD spectra show that ferric hydroxide is the main initial component of the clogging materials. Other compounds such as akaganeite, hematite and goethite are products from ferric hydroxide transformation. Therefore, the clogging materials are a mixture of ferric hydroxide and its converted products. The clogging materials commonly exist in an amorphous form with a cluster microstructure when viewed under SEM. Secondly, this work uses a continuous flow column to simulate clogging in the laboratory, and the clogging materials are analyzed with XRD and SEM. The chemical analysis indicates that the iron content of the clogging materials from the experiment is 45.43%. XRD spectra show that hematite is the only compound detected. The clogging materials generated experimentally are also in amorphous cluster microstructure when viewed under SEM.  相似文献   

The effect of grain size on the Cu, Pb, Ni, Cd speciation and distribution in sediments: a case study of Dongping Lake, China     

Ying Zhu  Xiaodong Zou  Suping Feng  Houquan Tang 《Environmental Geology》2006,50(5):753-759

This paper examines the surface sediments collected from Dongping Lake in China for speciation and distribution of toxic heavy metals (Cu, Pb, Ni, Cd) in different grain size fractions, and for the factors that need to be considered in potential hazard of metals to the environment. Four grain size fractions (<63, 63–78, 78–163 and 163–280 μm), divided in wet condition, and bulk samples less than 280 μm in diameter were analyzed for their distribution, density and appearance. A three-stage extraction procedure following the BCR protocol was used to chemically fractionate metals into “acid soluble”, “reducible”, “oxidizable” and “residual” fractions. Correlation analysis was used to analyze the datasets. The results showed that <63 μm grain size part constitutes the major proportion of the sediments, but its density is the smallest among the four grain size fractions. In general, the metal content curve against grain size presents “S” distribution, and the highest concentrations do not exist in <63 μm grain size. Appearance observation indicates that the adsorbed substance increases gradually along with the decreasing grain size. The dominant speciation of elements and the extent of pollution are responsible for the metal distribution in different grain size sediments. While studying bioavailability and mobilization of metals, it is advisable to take metal speciation, grain size distribution and density into consideration.  相似文献