跨断层隔震管道分析

埋地管道在断层错动作用下的内力分析及其抗震措施一直是生命线工程的一个重要问题与研究热点。对地下管道在断层错位下的响应计算,取得的成果较多,比较经典的有Newmark-Hall方法和Kennedy方法。后来又出现基于壳模型的简化方法,如高田至郎提出的简化计算方法等。相对来讲,关于管道抗震措施的研究成果较少。本文提出一种抗震措施,进行了基于壳模型的有限元动力数值模拟,并与4种松到中密场地土条件下的埋地管道断层错位响应进行对比分析。计算结果表明,本方法中三种长度管道的最大轴向拉应变远小于埋地管道的最大轴向拉应变,而且最大轴向压应变亦不大。     

国外对海底电缆管道违法行为处罚对我国的启示 ——以新西兰和澳大利亚为例

近年来,随着海洋油气资源的大规模开发以及跨海电力和通信需求的增加,我国海底电缆管道建设得到迅速发展,近海海底电缆管道分布愈来愈密集,同时与之相关的违法行为也日益增多。目前,我国尚未出台海底电缆管道保护法,现有的处罚规定较为分散、模糊,且处罚力度小,甚至处罚规定之间存在混乱和矛盾的问题,导致难以对海底电缆管道违法行为实施有效打击。澳大利亚和新西兰作为海洋管理经验相对成熟的国家,对海底电缆管道的法律保护较为成熟,其中对海底电缆管道违法行为的处罚分类和方式等,有诸多值得我国学习之处。基于此,文章从违法行为处罚角度深入分析我国海底电缆管道管理与保护的相关制度现状,介绍新西兰和澳大利亚海底电缆管道法律制度概况及处罚规定的特点并与我国进行比较,为完善我国海底电缆管道违法行为的处罚规定和今后的海底电缆管道立法提出了在《中华人民共和国刑法》中增设破坏海底电缆管道罪;制定《海底电缆管道法》等建议。     

Subsea pipeline walking with velocity dependent seabed friction

With the increase in demand and supply gap in the oil and gas industry, new developments of oil and gasinfrastructure are moving into deeper water. This requires design and construction of long high temperature and high pressure pipelines from deep sea to shore. These pipelines are subjected to cyclic expansion during operating cycles. Accumulated axial movement due to repeated thermal cycles may lead to global displacement referred to as ‘walking’. Walking rates depend on the restraint associated with seabed friction. In conventional analyses, seabed friction is independent of the rate of thermal loading and expansion but it has been recognised that the sliding resistance between a pipe and the seabed varies with velocity, partly due to drainage effects. In this paper a numerical model is used to explore the effect of velocity-dependent seabed friction. A velocity-dependent friction model is implemented in commercial software ABAQUS and validated via single element and simple (flat seabed) pipeline cases. This model features upper and lower friction limits, with a transition that occurs as an exponential function of velocity. A parametric study is performed using differing rates of heating and cool-down in walking situations driven by seabed slope, SCR end tension and the difference between heat up and cool down rates. The walking behaviour is compared to cases with constant friction and solutions are proposed to express the velocity-dependent response in terms of an equivalent constant friction. These equivalent friction values can then be applied in existing simple solutions or more complex numerical analyses, as a short cut method to account for velocity-dependent friction.     

Wake II model for hydrodynamic forces on marine pipelines including waves and currents

The Wake II model for the determination of the hydrodynamic forces on marine pipelines is extended to include currents and waves. There are two main differences between the Wake II and the traditional model. First, in the Wake II model the velocity is modified to include the pipe's encounter with the wake flow when the velocity reverses. Second, the model uses time dependent drag and lift coefficients. The flow field is assumed to be the linear superposition of regular waves and uniform current and is treated as wave only but in two different phases. The model requires eight empirical parameters that are obtained from comparisons with field data for various Keulegan–Carpenter numbers and current to wave ratios. The effective velocity and the force predictions are compared with field data from Exxon Production Research Company and with the conventional model. The model gives satisfactory results and predicts lift forces that in shape, magnitude and phase relative to the velocity are in very close agreement with measured forces. For the horizontal forces the results are very accurate. A substantial improvement is obtained over the predictions with the conventional model. This work is applicable to the design of submarine pipelines laying on the sea bottom in water depths where waves or waves and currents contribute to the hydrodynamic forces.     

顶管施工对相邻平行地下管线位移影响因素分析

顶管施工引起的管道周围土体移动会对相邻地下管线造成危害。采用三维有限元方法分析了顶管施工引起的相邻平行地下管线的位移,研究了注浆、纠偏、离顶管距离的远近、地下管线埋深、管线与土体弹性模量比及不同管材对地下管线位移的影响。计算结果表明,注浆与纠偏压力越大,地下管线的位移越大;地下管线距离顶管越远,引起的位移越小;地下管线弹性模量越小,产生的位移越大。     

海管碎石保护结构抵抗拖锚危害的模型试验研究

船舶走锚时可能对海底管线造成破坏,实际工程中常用碎石保护结构来对海底管道进行保护。为了研究这种结构的保护效果和保护机理,在大型试验槽中对三种尺寸模型锚进行了模型试验。在试验中测量了锚爪尖端位置和锚爪力在保护结构中的变化,得到锚体从细砂进入保护结构时的运动过程和运动规律,据此研究了碎石保护结构对海底管线的保护效果并分析了保护机理。     

波流联合作用下掺氢输气海管泄漏扩散研究

由于氢气密度低,泄漏后的掺氢天然气在海洋波流作用下的浮升扩散行为有别于纯天然气,其泄漏扩散规律有待明晰。利用计算流体力学方法数值模拟了波流联合作用下掺氢输气海管泄漏扩散的过程,结果表明气体泄漏的过程可分为泄漏初期、向上浮升以及横向迁移3个阶段。当掺氢比φH2 <50%时,氢气泡的运动轨迹受天然气泡的影响显著。气体浮升高度和扩散直径的变化与时间成正相关,且随着掺氢比的增大,泄漏气体到达液面所需的时间延长。天然气泡和氢气泡直径在上升的过程中都逐渐增大,两者的浮升速度随浮升高度的增加先增大后减小,天然气泡的浮升速度衰减更快。氢气泡直径随掺氢量的增加而增大,天然气泡直径随掺氢量的增大而减小,两者的上升速度随着掺氢量的增大都表现出先增大后减小的趋势,且氢气泡的上升速度大于天然气泡的上升速度。波长和海流流速越大,泄漏气体的扩散直径越大。     

基于缓冲区的电力管网重复管线合并算法

针对电力地下管网数据核查过程中因为数据迁移或者数据更新等其他原因导致的电力管线重复问题,提出了一种基于缓冲区的地理拓扑关系判断方法来检测并合并重复管线。在服从电力管线布局原则下,首先,对电力管线进行插值处理;然后,构造出管线缓冲区,其缓冲半径受插值距离调节,在此缓冲范围可以判断出地理点线包含关系;最后,根据不同的地理点线包含关系可以分析出管线间的线-线拓扑关系,从而可以判断出是否存在重复管线从而采取相应的重复管线处理措施。实验结果表明,提出的方法能够高效准确地处理电力管网数据核查中的重复管线问题。     

Analysis on Interface Shear Stress of Thermally Insulated Ocean Pipelines Under Installation

1.IntroductionMost of the crude oil producedfromoffshore China has a highcontent of wax,which makesthe oilagglomerate at hightemperature.Heat preservation measures,therefore,must be adopted to maintainthe temperature higher thanthe oil’s pour point,sotha…     

Buckle propagation in pipelines with non-uniform thickness

Finite element solutions for the steady-state buckle propagation pressure in a pipeline with non-uniform thickness are given. The results are useful in finding buckle propagation pressures in corroded pipelines. It has been found that when corrosion is equal to or less than 10% of the original pipeline thickness, the pipeline collapses in an overall shell buckling mode; otherwise, the pipeline experiences local buckling. The propagation pressure decreases with both the thickness and angular extent of the reduced section, but the rate of decrease with thickness reduction is almost independent of the angular extent of corrosion when it is greater than 90°.