深海海底管线自沉过程数值模拟研究

发布时间：2018-04-02 14:18

本文选题：海底管线　切入点：自沉过程　出处：《天津大学》2014年硕士论文

【摘要】：海底管线是连接油井与平台、平台与陆上储运设施的油气输送工具,具有安全、稳定、经济、输送量大等优点,是海洋油气输运系统的重要组成部分。海底管线的铺设方式分为裸置与埋置两种,不论采取何种方式,海底管线在铺设后,由于自重作用将开始自沉过程,管线逐渐嵌入海床土体,最终达到管土平衡的状态。由于海底环境与陆上不同,在自沉过程中,海底管线受多种荷载的联合影响,易产生较大的变形而失稳,造成巨大的经济损失和环境污染,因此海底管线的安全性和稳定性在海洋油气开发中尤为重要。通过有限元软件ABAQUS,应用Mohr-Coulomb本构关系,建立深海海底管土相互作用模型,模拟海底裸置与埋置管线的自沉过程。通过设置初始地应力平衡,管土接触,重力、浮力施加,土体排水固结等分析步,计算裸置和埋置管线、土体竖直方向的位移,并通过大量计算,探究管线和土体相关参数的变化对自沉过程的影响。计算结果显示,对于裸置管线,土体呈现沉降趋势,且参数的改变使土体越容易发生塑性屈服,土体的竖直方向位移量越大;对于埋置管线,土体呈现隆起趋势,且当管线埋深较浅、管线上方土体重量不大时,参数的改变使管线的平均密度与周围土体的密度相差越大、土体越容易发生塑性屈服,土体的竖直方向位移量越大。同时通过在裸置管线模型中设定生死单元的方式使部分土体失效,模拟海底悬跨管线的自沉过程,并探究悬跨长度对自沉过程的影响。计算结果显示,当管线悬跨长度较小时,土体竖直方向位移与管线未悬跨时的数值相接近,略有增长;一旦管线悬跨长度过大,管线两端支撑土体即被压溃,管线将产生大变形,十分危险。因此在海底管线安装与维护中,一定要采取有效措施降低悬跨长度,保证管线运营安全。
[Abstract]:Submarine pipeline is an oil and gas transportation tool connecting oil well and platform, platform and onshore storage and transportation facilities. It has the advantages of safety, stability, economy and large transportation capacity. It is an important part of offshore oil and gas transportation system.The laying mode of submarine pipeline can be divided into naked and buried. No matter what way, after laying the submarine pipeline, the self-sinking process will begin due to self-gravity, and the pipeline will be embedded into the seabed soil gradually, and finally reach the state of pipe and soil balance.Because the submarine environment is different from the land, during the process of self-sinking, the submarine pipeline is affected by the combination of various loads, and it is easy to produce large deformation and instability, resulting in huge economic losses and environmental pollution.Therefore, the safety and stability of submarine pipelines are particularly important in offshore oil and gas development.By using the finite element software Abaqus and applying the Mohr-Coulomb constitutive relation, the model of the deep sea bottom tube-soil interaction is established, and the self-sinking process of the submarine bare and buried pipelines is simulated.By setting the initial geostress balance, pipe-soil contact, gravity, buoyancy, soil drainage and consolidation, the displacement of the bare and buried pipelines and the vertical direction of the soil is calculated, and a large number of calculations are carried out.To explore the influence of pipeline and soil related parameters on self-sinking process.The calculation results show that for the bare pipeline, the soil presents a settlement trend, and the change of parameters makes the soil more prone to plastic yield, and the vertical displacement of the soil is larger; for the buried pipeline, the soil shows a uplift trend.When the buried depth of the pipeline is shallow and the weight of the soil above the pipeline is small, the variation of the parameters makes the difference between the average density of the pipeline and the surrounding soil mass greater, the more prone to plastic yield of the soil, the larger the vertical displacement of the soil.At the same time, by setting the birth and death element in the model of bare pipeline, the partial soil is invalid, and the self-sinking process of submarine overhanging pipeline is simulated, and the influence of the length of suspended span on the self-sinking process is explored.The calculation results show that the vertical displacement of soil is close to that of the pipeline when the length of the suspended span is small, and increases slightly; once the length of the suspended span of the pipeline is too large, the soil supported at both ends of the pipeline will be crushed.The pipeline will be deformed and very dangerous.Therefore, in the installation and maintenance of submarine pipelines, effective measures must be taken to reduce the length of suspension span to ensure the safety of pipeline operation.
【学位授予单位】：天津大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：P756.2;TE832

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