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81.
Feasible numerical method for a structural analysis of a pipeline configuration during the installation process is presented. The method considers the whole pipeline, which is partially suspended and partially laid-on a seabed, as a single continuous segment, and is valid for a complete range of laying angles between 0°–90°, i.e., valid for both S-lay and J-lay configurations. The method accounts for a pipeline–seabed interaction and the pipeline is modeled by means of nonlinear large deformation beam theory. The numerical solution is carried out in an incremental-iterative manner by following the actual pipeline installation process, and thus allowing efficient treatment of pipeline-seabed interaction circumventing the further complexities with contact detection. At each increment, the length of the pipeline is increased and new sequential equilibrium configuration is assessed by direct minimization of a total potential energy approximated as a Riemann sum, which yields algebraic system of nonlinear finite difference equations that is further solved by iterations with Newton-Raphson technique. The simplicity, flexibility and robustness of the proposed method allow to enhance the efficiency of engineering calculations and design. Accounting for a bending stiffness in a suspended part allows analyzing variations in laying angle and lay tension independently. The method convergence is validated and compared with Abaqus. The results are in an excellent agreement. Moreover, the comparison with Abaqus shows that for the selected parameters the assumption that the pipeline is inextensible and unshearable is very reasonable. Representative parametric study is conducted to demonstrate the feasibility of the method. Parametric study considers the effects of laying angle (0°–90°), lay tension, laying water depth (up to 3000 m) and seabed stiffness. 相似文献
82.
针对利用最小二乘配置处理多波束测深数据,存在二次曲面数学模型通常无法精确表征海底地形的整体变化趋势以及观测数据存在粗差或异常点时,常规方法给出的协方差函数不能精确表征其统计特性的问题,本文提出了一种抗差最小二乘配置迭代解法。该方法首先进行协方差函数和观测值方差阵初始化,以多面函数拟合趋势项,然后应用等价权抗差估计并通过迭代计算,最终给出稳健的协方差函数参数解及最小二乘配置解。利用本文提出的方法及传统的方法处理实测的多波束测深数据,试验结果表明,相比于传统的方法,本文提出的方法能够较好地表征海底地形的整体变化趋势,一定程度上克服了多波束测深数据中粗差或异常点的影响。相比于传统的抗差方法,本文方法更为有效地识别出测深数据中异常点,推估效果较好,具有稳健性。 相似文献
83.
《Marine Policy》2016
The 1982 United Nations Convention on the Law of the Sea declares the seabed beyond national jurisdiction and its mineral resources as the “common heritage of mankind” (CHM). This article examines the operationalisation of the CHM principle in the international seabed mining regime, with focus placed on the sharing of benefits derived from mining. The article begins by providing an overview of the CHM principle, before examining four modalities provided for in the Convention, both institutional and substantial, and their role in giving effect to the CHM principle: (1) financial benefits; (2) the “Enterprise”; (3) the parallel system of reserved areas; and, (4) marine scientific research. Finally, overarching issues are discussed and some suggestions on ways forward are presented. The article considers that the deep seabed mining regime is not yet ready to effectively share the benefits derived from the common heritage of mankind. In particular, the future of the Enterprise is uncertain and changes to the so-called parallel system that affect the CHM have received minimal discussion. Moreover, a lack of publicly available research data related to seabed mining is hindering current benefits for humankind. However, work is underway at the International Seabed Authority to establish rules and policies with respect to the sharing of financial benefits. While the CHM principle remains largely untested, approaches that are transparent, inclusive, accountable, and equitable are more likely to be successful. 相似文献
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The size of individual mining blocks for polymetallic nodule extraction seems to be rather small, not more than 100 km2 in the French mining claim. Even when adding an additional resedimentation zone to the directly impacted area, the size of the affected seabed would remain below 200 km2. We assume that even rare species in the abyss inhabit larger areas and propose discussions of the International Seabed Authority and other stakeholders for the different subregions on mining strategies from the perspective of exploitation versus species extinction and conservation. Although impacts of waste disposal at the abyssal seafloor are different from those of nodule mining, the 200 km2 concept may also be applied. 相似文献
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针对裸露悬跨海底管道,考虑线弹性海床刚度,利用梁的小挠度理论,研究管道在自重作用下的变形和内力,推导给出了未脱离海床的管道段和悬跨管道段的变形和内力公式。在跨度较大的悬跨情况下,悬跨管道段较大的向下弯曲变形可能引起海床上管道脱离海床而翘起。建立管道翘起的判定准则,对于翘起情况推导相应的计算公式,通过算例给出翘起情况下管道的变形和内力。通过计算分析发现:工程上多数悬跨是翘起情况,没有翘起的计算公式只适应于跨度较小的悬跨管道。同时翘起情况下不同海床刚度对悬跨管道无量纲内力影响不大。 相似文献
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