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海流作用下海底管道侧向失稳滑滚机制及分析模型研究
Alternative TitleSliding-rolling Mechanism and Analysis Model for the Lateral Instability of the Pipeline in Currents
徐凯
Thesis Advisor高福平
2019-05-29
Degree Grantor中国科学院大学
Place of Conferral北京
Subtype硕士
Degree Discipline工程力学
Keyword海底管道,在位稳定性,滑滚机制,滑滚比
Abstract

海流作用下海底管道的侧向失稳过程中,管土界面通常存在滑动和滚动两种运动模式。前人对于管土相互作用分析模型的研究很少涉及失稳过程中的滚动模式。本文针对该问题分别开展了机械加载试验和水动力试验研究,探究了管道侧向失稳过程中的滑滚机制,并建立了管道滑滚失稳的分析模型。

利用机械加载装置开展了系列模型试验,研究管道侧向失稳过程中的侧向土阻力特性及管道运动特征。试验结果表明,极限土阻力随着管道水下无量纲重量的增加而增大,相应的无量纲土阻力系数却随之逐渐减小并最终趋于稳定值;当管道水下无量纲重量不变时,初始嵌入深度与管径比越大,极限土阻力及其无量纲系数也越大。流固土耦合水槽中开展的系列水动力试验结果也表明,海流作用下,表征管道侧向失稳的临界Froude数随着管道水下无量纲重量和初始嵌入深度与管径比的增大而增大。

机械加载和水动力试验均发现,在管道侧向失稳过程中,管土界面同时存在滑动和滚动两种运动模式。采用滑滚比的概念及计算方法定量表征管道的滑滚运动;根据量纲分析探究了滑滚比随着管道相对水平位移、无量纲水下重量、嵌入深度与管径比等因素的变化规律。当侧向位移较小时滑动占据主导地位,之后管道逐渐易于滚动,随着侧向位移的发展,滑滚比呈现非线性减小趋势。滑滚比与管道水下无量纲重量和初始嵌入深度与管径比之间均呈现正相关的关系。

采用数值方法模拟了管道侧向失稳的准静态过程,进一步研究了管道周围土体塑性区和位移增量矢量场的发展,并利用机械加载试验结果对数值模型进行了验证。根据滚动摩擦机理和准静态的力矩平衡条件,建立了管道纯滚动失稳的预测模型;根据界面滑动摩擦机理和准静态的受力平衡条件,建立了管道纯滑动失稳的预测模型。进行关联分析,通过滑滚比建立了管道滑滚失稳的分析模型。

Other Abstract

Previous studies on the lateral instability of the pipeline seldom paid attention to the rolling motion at the pipe-soil interface, while in the detailed lateral breakout process of submarine pipelines under ocean currents, the sliding and the rolling motion could be coexistent. In this thesis, the mechanical loading tests, hydrodynamic tests were carried out to investigate the sliding-rolling mechanism in the process of lateral instability of the submarine pipelines. Eventually an analysis model for pipeline sliding-rolling instability is established.

A series of mechanical loading tests were carried out to investigate the characteristics of the soil resistance and the pipeline motion in the lateral instability of submarined pipelines. The test results indicate that the ultimate lateral soil resistance of the pipeline increases with the increase of the dimensionless submerged pipeline weight, but the corresponding dimensionless soil resistance coefficient decreases gradually and finally approaches a stable value. When the dimensionless submerged weight of the pipeline remains unchanged, the ultimate lateral soil resistance and its dimensionless coefficient increase with the increase of the ratio of the initial pipeline embedment to the diameter of the pipeline. Meanwhile, a series of hydrodynamic tests were conducted in a large fluid-structure-soil interaction flume. The results indicate that under ocean currents, the critical Froude number of the pipeline instability increases with the increase of the dimensionless submerged pipeline weight and the ratio of the initial pipeline embedment to the diameter of the pipeline.

In mechanical loading and hydrodynamic tests, it is found that the sliding and the rolling exist simultaneously at the pipe-soil interface in the lateral instability of submarine pipelines. The sliding-to-rolling ratio was introduced to characterize the sliding-rolling motion in the process of the pipeline lateral instability. On the basis of the dimensional analysis, the variation of the sliding-to-rolling ratio with the relative lateral displacement, the dimensionless submerged weight, the ratio of the initial   embedment to the diameter of the pipeline was discussed. When the lateral displacement is small, the sliding dominates, and then the pipeline gradually tends more to roll. With the development of relative lateral displacement, the sliding-to-rolling ratio shows a nonlinear decreasing trend. There exists a positive correlation between the sliding-to-rolling ratio and the dimensionless submerged weight, or the ratio of the initial embedment to the diameter of the pipeline.

The numerical method was used to simulate the quasi-static process of the pipeline lateral instability, and the plastic zone of seabed soil and displacement increment vector field in the process of the pipeline lateral instability were further investigated. The numerical model was verified by the results of the mechanical loading test. On the basis of the rolling friction mechanism and the principle of quasi-static torque balance, the prediction model for the pipeline lateral rolling instability is given. On the basis of the interfacial sliding friction mechanism and the principle of quasi-static force balance, the prediction model for the pipeline lateral sliding instability is given. Making the correlation analysis, an analysis model for the pipeline sliding and rolling instability is established.

Language中文
Document Type学位论文
Identifierhttp://dspace.imech.ac.cn/handle/311007/79114
Collection流固耦合系统力学重点实验室
Recommended Citation
GB/T 7714
徐凯. 海流作用下海底管道侧向失稳滑滚机制及分析模型研究[D]. 北京. 中国科学院大学,2019.
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