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海底沉积物取样技术对大洋诸多科学研究来说非常重要,各种研究目标的实现与沉积物样品的质量息息相关.在使用常规管状取样器对松软或轻微固结的沉积物取样时,沉积物样品的扰动总是不可避免的.以机械手持式沉积物取样器为原型机,建立了管状取样器的取样过程模型,分析了沉积物样品的扰动机理;采用球形孔扩张理论获得了沉积物土体受到取样管挤压扩张的理论解;结合太平洋具体沉积物土体物理力学参数,对管状取样器取样造成沉积物扰动的状况给出了一个定量描述,并且提出取样管壁的厚度是减小沉积物扰动的关键参数. 相似文献
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重力活塞取样器贯入深度研究对于取样效率的提高和仪器安全有着重要影响,根据取样海底沉积物类型及工程参数对取样器可贯入深度进行预判是研究的重点。基于重力活塞取样器结构,设计并制造了重量可调的重力取样器模型,增加了底质桶与支架等配套设施。按照控制变量法分别设计了针对取样器质量、贯入速度及沉积物类型的试验。试验结果表明,底质类型、取样器质量和贯入速度都可以对贯入深度产生不同程度的影响。在现有重力取样器贯入深度公式的基础上,根据本次试验得到的数据对其进行修正。改进后的公式计算结果与原来相比误差更小、更接近于真实取样数据。 相似文献
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黄河口及渤海中南部沉积物工程特性及其机理 总被引:3,自引:0,他引:3
采用Kasten取样器从黄河口及渤海湾中南部海底沉积物中取样,对样品通过土工性质、微结构研究以及粘土矿物分析,阐明本研究区三维空间展布的海底沉积物形成机理及其工程地质规律,论证水动力作用和斜坡不稳定性对工程特性和微结构的重要影响. 相似文献
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本文探讨了海洋沉积物的工程特性,以及为海岸工程地基而进行的海洋工程地质勘探方法。包括海洋工程地质测绘,海底钻探(Wirth型、MAS—73型、koken型及Maricor型海底钻探机械设备)、用重力、活塞、箱式取样器(管)进行水下取样、以及洋底沉积物钻孔剪切试验装置、旁压试验装置。 相似文献
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为了获得连续、低扰动、超长的深海海底沉积物样品,研制了一套可应用于最大水深6 000 m,最长取样可达25 m的可视可控轻型沉积物柱状取样系统。本套设备主要包括甲板控制单元、取样系统和立式收放机构3部分。在取样过程中,本系统充分利用动能和深海液压锤夯击双动力组合,即取样过程包括前期的重力贯入和后期的夯击取样两个过程。液压锤夯击机构的配置使取样器在不显著增加自身重量的前提下,完成超长、连续、低扰动的深海沉积物柱状样采集工作。取样器的组合与拆卸采用立式吊装的方式,极大地降低了取样过程中的工作量和所需甲板作业空间。水下监测系统的配置解决了以往盲采样的弊端。除此之外,本取样器还设有多个标准通用端口,可以扩展为多种设备的集成平台,完成多种数据的采集。目前本套设备已经成功进行了海试,并作为主要沉积物取样设备成功应用于多个海上调查航次,取得了一系列连续、低扰动的柱状样品,有效地提高了我国深海可视可控柱状取样的技术水平。 相似文献
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Steep wave impact pressures and the structural dynamic response of floating production storage and offloading platform (FPSO) bows are studied using 1:80 scale segmented, instrumented models. The construction of these segmented models is discussed. The ‘new-wave’ theory is adopted and extended to generate steep waves and a limiting form of steep wave that might be found in deep water is proposed. A comparison between linear theoretical, experimental and suggested wave models is made. Experimental results with systemically varying parameters are presented. 相似文献
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Kevin J. Maki Donghee Lee Armin W. Troesch Nickolas Vlahopoulos 《Ocean Engineering》2011,38(4):621-629
In this paper a hydroelastic method for the design of marine structures is used to study the impact of a wedge-shaped body onto a calm free-surface. The method combines computational fluid dynamics and dynamic finite-element techniques to predict the hydroelastic response of a structure in the time domain. The basic idea of the method is to predict the stress field on the fluid-structure interface due to rigid-body impact, and then to transfer the information to a wet modal model. The one-way transfer of information from the fluid simulation to the structure has two important advantages with respect to a fully coupled simulation: a single rigid-body motion computation can be reused for subsequent analyses after the structure has been redesigned, and cost of the fluid dynamic simulation is not increased due to iteration which is required in coupled simulations. The maximum displacement of an elastic wedge during the impact and penetration stages are compared with published results from a fully coupled theoretical model and a fully coupled numerical solver. The present method requires approximation of the flexural added mass, and the comparison with other results shows that the approximation is satisfactory for predicting maximum displacement. 相似文献
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Steep wave impact pressures and the structural dynamic response of FPSO bows are studied using 1:80 scale instrumented models and time domain simulation. Comparisons are made between experimental and calculated impacts and associated pressures. A simple time history simulation method for bow loading in (non-linear) random seas is developed. Simplified design rules for curved bows are proposed. The rules account for the effect of the size of the loaded area on the average pressure, the rise and decay times of the pressure and the dynamic amplification of the response. 相似文献
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This paper considers wave impacts on baffles, on baffles or decks adjacent to a vertical wall, and on porous seawalls and/or sea beds. For seawalls and vertical baffles, impacts can occur in steep waves, whilst a deck can be struck from below by a rising wave crest either in open sea or in a tank with standing waves (sloshing). A simple analytical model for the pressure impulse, P, due to a wave of idealized geometry and dynamics is developed and applied to the following geometries with impermeable surfaces:
- •horizontal wave impact onto a vertical wall with a deck at the waterline,
- •vertical wave impact under a deck in the same configuration (equivalent to vertical water impact of a horizontal plate),
- •horizontal wave impact onto a surface-piercing vertical baffle in open sea,
- •as for 3. but with the baffle in front of a wall,
- •as for 4. but with a deck extending from the vertical wall to the baffle,
- •bottom-mounted baffle in front of a wall with impact occurring on the wall.
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This paper presents a method to statistically predict the magnitude of impact pressure (including extreme values) produced by deep water waves breaking on a circular cylinder representing a column of an ocean structure. Breaking waves defined here are not those whose tops are blown off by the wind but those whose breaking is associated with steepness. The probability density function of wave period associated with breaking waves is derived for a specified wave spectrum, and then converted to the probability density function of impact pressure. Impacts caused by two different breaking conditions are considered; one is the impact associated with waves breaking in close proximity to the column, the other is an impact caused by waves approaching the column after they have broken. As an example of the application of the present method, numerical computations are carried out for a wave spectrum obtained from measured data in the North Atlantic. 相似文献
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WANG Deyu CHEN Tieyun XIN Guonian
Associate Professor School of Naval Architecture Ocean Engineering Shanghai Jiaotong University 《中国海洋工程》1998,(2)
The impact buckling of a laminated composite bar is investigated in case of one of its endsmoving due to axial impact compression.The governing equations considering the first-order sheardeformation effect are derived by the Hamilton principle and solved by the finite difference method.Thecritical axial shortness is determined by the B-R cirterion.The given example is used to highlight the in-fluences of initial imperfection,impact velocity,stress wave and coupled stiffness.It is found that theunsymmetrically laminated bar has a quite different dynamic buckling behaviour from that of thesymmetrically laminated bar. 相似文献
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M.S.Seif S.M.Mousaviraad S.H.Saddathosseini 《中国海洋工程》2004,18(4):595-604
The effect of the asymmetric water entry over a submerged part of a ship on the hydredynamic impact is investigated numerically. A wedge hotly is considered and the problem is assumed to be two-dimensional. The results of symmetric and asymmetric impacts are compared. The effect is found significant in the numerical simulation. The maximum hydrodynamic pressure at a heel angle of 10 degrees becomes about 95% more than that of the symmetric entry. The result of the present work proves the importance of asymmetrical hydrodynamic impact loading for structural design of a ship. Besides, the numerical procedure is not limited to a wedge type cross section and it is possible to apply it for any real geometry of ships and high-speed craft. 相似文献
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三亚湾秋季桡足类分布与种类组成及对浮游植物现存量的摄食压力 总被引:6,自引:0,他引:6
秋季(11月底),桡足类针刺拟哲水蚤(Paracalanusaculeatus)和拟哲水蚤(Paracalanus)幼体为三亚湾优势种;强额孔雀哲水蚤(Pavocalanuscrassirostris)对浮游植物现存量的平均日摄食压力最大,各站平均为叶绿素a的(6.79±6.82)%,其次是针刺拟哲水蚤,平均为(5.97±5.67)%,亚强次真哲水蚤(Subeucalanussubcrassus)对浮游植物现存量的摄食压力较低,平均为(2.20±2.33)%,桡足类在秋季对浮游植物的日摄食压力占叶绿素a的(22.31±18.92)%。三亚湾属于生产力偏低的海区,对初级生产力的摄食压力以中型浮游动物针刺拟哲水蚤、锯缘拟哲水蚤(Paracalanusserrulus)、红纺锤水蚤(Acartiaerythraea)、微驼背隆哲水蚤(Acro calanusgracilis)和驼背隆哲水蚤(Acrocalanusgibber)为主,小型浮游动物的摄食压力也占一定的比例。 相似文献
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《Marine Policy》2014
General data would seem to indicate that aquaculture and extractive fishing are primary activities with a greater presence in developing and less industrial economies. Despite the scant importance of fishing in the EU (in terms of GDP and employment), it remains a focal point of EU activity by means of the Common Fisheries Policy (CFP). The CFP establishes measures aimed at supporting fishing, often assuming that it is localized activity in rural, less developed regions. This study looks to quantify the importance and economic and social impact of primary fisheries and aquaculture activities in a European urban region (the area of the Ria of Vigo, in Galicia, Spain) through an exercise based on an input–output approach. The exercise carried out will provide results that imply a total impact that could reach around 7% of the study region's income and employment. From these results it can be concluded that fishing as a primary activity may also be relevant in EU urban areas; therefore, fishery management and support measures within the CFP should bear this differentiated reality in mind. 相似文献
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《Marine Policy》2014
Delivering the ambitious renewable energy targets set by the Scottish Government will require significant expenditures. Plans have been set out to develop 1.6 GW of marine (wave and tidal) energy capacity between 2010 and 2020 in the Pentland Firth and Orkney Waters area (off the north coast of Scotland) with construction costs estimated at £6 billion. This paper uses multi-sectoral economic models to explore the impact that these (temporary) expenditures could have on the Scottish economy. It is shown that the standard Input–Output (IO) modelling approach significantly overstates the employment and value added impacts compared to Computable General Equilibrium (CGE) methods—in which short-run scarcity of factors of production are explicitly modelled. CGE results (under myopic and forward-looking model specifications) produce smaller impacts during the timespan of expenditures but, unlike IO methods, identify non-trivial “legacy effects” after the expenditures cease. 相似文献