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《中国海洋大学学报(自然科学版)》2017,(5)
随着海洋开发从浅水走向深水,各种特种船舶在海洋工程建设中发挥的作用日益重要。起重船是海洋工程建设的重要工程船舶,是海洋开发的必备工具。为了更好的开发利用海洋资源,有必要进行相关设备的研究。参考某回转式起重船的具体参数,结合该船工作时的具体过程,利用大型水动力分析软件OrcaFlex建立了该起重船回转起吊作业状态下的动力学分析简化模型。通过调节不同海况下的浪向,实现了对大型回转式起重船回转起吊作业过程的的动力学分析,得到了吊物就位时不同浪向下的与接收船甲板的碰撞力、吊缆张力等,对比并分析了不同浪向时吊缆的张力变化,确定了吊物的最小碰撞力和吊缆的张力大小及波浪方向,结合计算结果,给出了大型回转式起重船回转起吊作业的优化设计方案。 相似文献
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针对现有海上吊装模拟方法不能有效考虑浮吊船舶—系泊系统—吊物系统之间的动态耦合,难以实现基座回转、吊臂变幅连续模拟问题,基于Matlab/Simulink、ADAMS联合仿真平台建立了海上吊装作业全耦合动力分析模型,探究了中长周期波作用下波浪周期、吊缆收放、基座回转、吊臂变幅等参数变化对吊装作业系统动力响应的影响规律。结果表明,波浪周期接近吊物系统固有周期时会引发共振,导致吊物摇摆幅值显著增加。基座回转、吊臂变幅等因改变了吊物的空间位置从而引发了浮吊船舶倾覆力矩的变化,进而对浮吊船舶运动响应产生显著影响。当基座回转90°后,浮吊船舶的横倾角增加约2.74°。 相似文献
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近年来深水勘探已成为寻找油气的重要领域,白云凹陷在早中新世经历了复杂的构造沉积环境,解剖深水层序模式有利于揭示深水沉积演化规律。通过井震结合及属性分析对白云凹陷早中新世层序地层进行研究,识别出3个层序界面:ZJSB1(23.8 Ma),ZJSB2(22Ma),ZJSB3(21Ma)。其中ZJSB1、ZJSB3为重大不整合面,ZJSB2为水道下切侵蚀面。与之对应的界面发育3套层序:ZJSQ1,ZJSQ2,ZJSQ3。由于白云凹陷构造运动及古地貌的差异性,总结了2套深水层序模式:水道—深海披覆泥层序模式与块状搬运复合体—砂质碎屑流深海扇—水道—深海泥层序模式,在不同的演化阶段,前者主要受海平面的变化控制,而后者是受构造和海平面双重影响的。而同一地质时期古地貌又控制了沉积发育,高地势区发育下切水道,而低洼区发育深海披覆泥岩。因此,深水层序模式下研究深海沉积单元,对指导深水沉积和油气勘探具有极其重要的意义。 相似文献
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多筒型导管架基础下放安装过程筒顶开口,筒内气—水自由置换,浪溅区下放过程由于浮力、冲击载荷、附加质量、阻尼效应等因素影响具有很强的非线性。开展模型试验研究波浪荷载下外界控制因素对四筒导管架基础下放过程气垫响应、基础运动和吊缆张力响应的影响机理,探究气垫结构对基础下放过程附加质量和固有周期的影响。结果表明：初始下放过程,筒内气体积聚,气垫压力非线性增长,随着下放深度增大,气垫压力趋于稳定;气垫压力响应趋势与基础下放速度和开孔率相关,波浪荷载仅影响气垫响应幅值;筒型基础下放穿越浪溅区阶段受到砰击荷载作用,气垫结构对砰击荷载产生缓冲效果;考虑气垫—水柱耦合作用时,顶盖即将入水阶段,气弹簧和水弹簧耦合作用下整体刚度增大,基础固有周期出现减小趋势。 相似文献
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脐带缆是深海油气开发的关键设备之一,主要由钢管单元、电缆单元、光缆单元、护套及铠装单元组成。脐带缆在全寿命周期经过设计制造、储存、安装、在位运行、修复阶段,其每个阶段的可靠性并不是某个常数,而是随时间变化的函数,因此有必要对脐带缆全寿命周期可靠性的变化进行分析。建立某气田水下脐带缆在储存、安装、在位运行阶段的故障树模型,将其转化为多阶段贝叶斯网络模型进行建模分析,基于OREDA手册数据,假设部件寿命服从指数分布,对脐带缆存储、安装、在位运行阶段的可靠性进行分析,得到不同阶段脐带缆可靠性的变化曲线,并与可靠性框图方法进行对比分析。同时,通过引入条件可靠性对该方法进行了优化,分析脐带缆修复后的可靠性变化,以及对脐带缆关键部件进行重要度分析,针对薄弱环节提出改进措施。可靠性分析可为水下脐带缆的安全运行提供技术支持,同时也为海洋结构与设备的全寿命周期可靠性分析提供了一种方法参考。 相似文献
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在深海采矿车布放回收中,准确预报脐带缆在底部自由悬垂边界条件和顶部波浪载荷随机激励等共同影响下的动力响应是关键点之一。基于三维势流理论与集中质量法,结合水面支持船运动和海流联合激励,对深海布放回收中脐带缆的顶端张力等力学特性进行研究。结果表明：在布放回收过程中,轴向张力在结构载荷中占主要成分;由波浪引起的轴向张力极值与均值差距最大可达到54%;轴向张力的频谱存在双谱峰,分别为 0.14 Hz的主峰和0.10 Hz 的次峰;当浪向角为180°时,轴向张力处于峰谷。 相似文献
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《海洋地质与第四纪地质》2017,(6)
利用广州海洋地质调查局已有的2D地震资料,对南海南部北康盆地拗陷阶段中中新世地层内的地震反射结构进行了精细刻画。通过对地震反射同相轴振幅强度、连续性、接触关系、整体形态特征等要素的系统识别和总结,建立了5种典型的地震相类型。结合南海南部沉积盆地的构造-沉积演化特征,识别出了中中新世时期北康盆地内发育的深水沉积体类型,分别是半深海-深海细粒沉积体、三角洲前缘砂体、浊积体和小型浊积体水道。研究认为,三角洲前缘砂体和浊积体构成了研究区拗陷阶段的两大深水碎屑岩储集体类型,能够与下部断陷阶段的烃源岩和中中新世之后的深海-半深海细粒沉积体一起构成垂向上的生储盖组合,具有较好的油气勘探潜力。 相似文献
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Spar平台垂荡-纵摇耦合运动失稳机理 总被引：1，自引：0，他引：1
研究参数激励和强迫激励共同作用下Spar平台垂荡-纵摇耦合运动的失稳机理.考虑静稳性和排水体积的变化,推导平台的垂荡回复力和纵摇回复力矩表达式,建立规则波浪中平台垂荡-纵摇耦合的运动方程.以经典Spar平台为例,分析平台垂荡-纵摇耦合运动发生马休类型不稳定运动的条件以及平台运动失稳的形式,给出波高和波浪周期平面上平台因大幅运动失稳的参数域.结果表明,当波高相对较小时,波浪的临界周期接近于垂荡固有周期,平台失稳的形式为马休失稳;当波高相对较大时,波浪的临界周期远离垂荡固有周期,平台由于大幅摇摆运动而失稳. 相似文献
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Chandralata Raghukumar G. Sheelu P. A. Loka Bharathi Shanta Nair C. Mohandass 《Marine Georesources & Geotechnology》2001,19(1):1-16
In order to assess the impact of deep-sea mining on the in situ benthic life, we measured the microbial standing stock and concentration of organic nutrients in the deep-sea sediments of the Central Indian Ocean Basin in the Indian pioneer area. Sediments were collected using box core and grab samples during September 1996. The total bacterial numbers ranged from 10 10 -10 11 cells per g -1 dry weight sediment. There was a marginal decrease in the number of bacteria from surface to 30 cm depth, though the subsurface section registered a higher number than did the surface. The highest numbers were encountered at depths of 4-8 cm. The retrievable number of bacteria were two orders less in comparison with the direct total counts of bacteria. An almost homogeneous distribution of bacteria, total organic carbon, living biomass, and lipids throughout the depth of cores indicates active microbial and benthic processes in the deep sea sediments. On the other hand, a uniform distribution of total counts of bacteria, carbohydrates, and total organic carbon in all the cores indicates their stable nature and suggests that they can serve as useful parameters for long-term monitoring of the area after the benthic disturbance. Further studies on temporal variability in this region would not only verify the observed norms of distribution of these variables but would also help to understand restabilization processes after the simulated benthic disturbance. 相似文献
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Arne Schnack-Friedrichsen Angela M. Davis Jim D. Bennell Dei G. Huws 《Marine Georesources & Geotechnology》2001,19(4):221-243
The interdependence between the seismo-acoustic properties of a marine sediment and its geotechnical/physical parameters has been known for many years, and it has been postulated that this should allow the extraction of geotechnical information from seismic data. Though in the literature many correlations have been published for the surficial layer, there is a lack of information for greater sediment depths. In this article, a desktop study on a synthetic seafloor model illustrates how the application of published near-surface prediction equations to subsurface sediments (up to several tens of meters burial depth) can lead to spurious predictions. To test this further, acoustic and geotechnical properties were measured on a number of sediment core samples, some of which were subjected to loading in acoustically-equipped consolidation cells (oedometers) to simulate greater burial depth conditions. For low effective pressures (representing small burial depths extending to around 10 meters subsurface), the general applicability of established relationships was confirmed: the prediction of porosity, bulk density, and mean grain size from acoustic velocity and impedance appears generally possible for the investigated sedimentary environments. As effective pressure increases through, the observed relationships deviate more and more from the established ones for the near-surface area. For the samples tested in this study, in some instances increasing pressure even resulted in decreasing velocities. There are several possible explanations for this abnormal behavior, including the presence of gas, overconsolidation, or bimodal grain size distribution. The results indicate that an appropriate depth correction must be introduced into the published prediction equations in order to obtain reliable estimates of physical sediment properties for greater subsurface depths. 相似文献
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Geoacoustic Inversion via Genetic Algorithm and Its Application to Manganese Sediment Identification
An acoustic inversion method using a wide-band signal and two near field receivers is proposed and applied to multiple layered seabed models including a manganese sediment. The inversion problem can be formulated into a probabilistic model comprised of signals, a forward model, and additive noise. The forward model simulates wide-band signals, such as chirp signals, and is chosen to be the source-waveletconvolution plane wave modeling method. The wavelet matching technique, using weighted least-squares fitting, estimates the sediment sound-speed and thickness on which determination of the possible numerical ranges for a priori uniform distribution is based. The genetic algorithm is applied to a global optimization problem to find a maximum a posteriori solution for determined a priori search space. Here the object function is defined by an L 2 norm of the difference between measured and modeled signals. Not only the marginal pdf but also its statistics are calculated by numerical evaluation of integrals using the samples selected during importance sampling process of the genetic algorithm. 相似文献
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海上大直径钢管桩打桩过程中,桩周土体受到强烈扰动而发生强度弱化,掌握桩周土体强度弱化规律对于准确预测打桩过程、保证工程安全具有重要意义。为研究土体强度弱化规律,开展了环剪试验模拟打桩对桩周土体的扰动,测试土体强度随剪切速率的变化规律,建立了描述土体强度弱化规律的拟合公式,引入到打桩分析软件中。研究结果表明：土体的强度折减程度不仅与土体本身的性质有关还受到土体的埋深和剪切速率的影响,埋深越深土体强度折减程度越低,剪切速率越高土体强度折减越高,在打桩分析中可采用这里推荐的线性折减方法来模拟不同深度处土体强度的折减规律。 相似文献
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Shigehisa Nakamura 《Marine Geodesy》2000,23(1):55-61
Specific properties of the interannual sea level variations and annual tides in the Northwestern Pacific were studied. Several tide stations were monitored. The monthly mean sea level for the year of 1995 was analyzed at each tide station. A seismic event in 1995, some tectonic activity around the subject area, and the Kuroshio (the oceanic western boundary current) may possibly contaminate results which would have occurred from the astronomical annual tide alone. 相似文献
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The effect of different fixation and storage protocols on the flow cytometric (FCM) simultaneous analysis of bacterioplankton and phytoplankton in coastal seawater samples (Mediterranean coastal lagoons) was investigated. FCM measurements (cell number, fluorescence and scatter characteristics) were obtained through DAPI staining. Three fixatives [glutaraldehyde (GA), formaldehyde (FA) and paraformaldehyde (PFA)] and two storage (3 months duration) methods (5 °C and −196 °C) were tested. Two dominant populations were detected in studied samples: bacteria and eukaryotic picophytoplankton. Adding fixatives (2% final concentration) appears necessary to obtain FCM exhaustive counts of all the bacteria and phytoplanktonic cells. This was related to the permeation effect of fixatives which allowed a better DAPI staining of the cells. Maximum fluorescence, i.e. optimal staining of the cells was obtained with FA or PFA, and significant lower fluorescences with GA. Fixed samples stored at 5 °C induced rapid cell loss. Only storage in liquid nitrogen of samples fixed with FA or PFA, allows mid-term (≥4 months) preservation of bacteria or picophytoplankton cell numbers, and limited evolution of DAPI-induced fluorescence and scatter characteristics. 相似文献
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Oedometer tests have been carried out on 70 undisturbed surficial clays (at approximately 250 mm below the mudline), mostly collected by free-fall corers from sites widely scattered throughout the deep-sea North Atlantic. Acoustic measurements were also made, initially on contiguous samples and ultimately on the same sample using a geophysically instrumented oedometer which also collected electrical resistivity data. Apart from those quiescent areas below the carbonate compensation depth, such as north of the West Indies where very fine clays exist, most of the samples are silty clays whose geotechnical-geophysical properties are dependent on the type of clay minerals present (and their ability to take in moisture), the sand-size fraction, and the quantity of carbonate present. Thus the pure clays have high compressibilities which decrease on the addition of coarse particles, while the converse is true for the acoustic parameters, these increasing with the sand fraction. Using the notion of the intrinsic compression line for all samples, and comparison to it of the measured compression curves, it is clear that, contrary to some previously held ideas, most deep-sea clays are normally consolidated; the addition of carbonate has the effect of creating an open, stronger sediment skeleton. Interestingly, where information is available, the variation with depth of a sample's acoustic velocity follows the void ratio pressure relationship of the compression curve. This allows the construction of an in-situ sediment compression curve using the in-situ geophysical observations. 相似文献
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《海洋学报(英文版)》2014,(9):F0003-F0003
<正>Acta Oceanologica Sinica(AOS)is a comprehensive academic journal edited by the Editorial Committee of Acta Oceanologica Sinica and is designed to provide a forum for important research papers of the marine scientific community which reflect the information on a worldwide basis.The journal publishes scholarly papers on marine science and technology,including physics,chemistry,biology, 相似文献